STREET PERFORMANCE & RACING PISTON TECH

Insight into the world of go-fast slugs.

by Mike Mavrigian

photos by author

It should come as no surprise that piston technology has evolved over recent years, largely due to superior material availability and the advent of precision CNC-machining capabilities. While a custom piston order may have once required four to six weeks or longer, computer modeling and CNC processes have cut the waiting time in some cases to a mere few days (naturally, depending on the piston maker’s schedule. Bear in mind that top piston makers are besieged by orders from pro race engine builders prior to the start of each season, so factor this into your expectations). For popular movers such as smallblock Chevy applications, many designs once viewed as “custom” in nature may now be available as in-stock items, ready to ship.
Here, we’ll focus on forged racing pistons. While hypereutectic pistons (high-silicon content castings that are much more dimensionally stable under thermal stresses than a common type aluminum casting) are perfectly adequate for high performance street motors, as well as many race applications, they’re nonetheless castings, which are less ductile than forgings. In other words, if it’s gonna break, a casting will tend to shatter as opposed to a forging, which will go “plastic” before it breaks through.
The two most common alloy materials used in today’s forged pistons are 2618 and 4032 aluminum. The 2618 material is a nearly pure aluminum with very little silicon content.
According to Probe’s Chris Huff, this material provides increased fatigue resistance, with a tendency to bend rather than crack.

4032 alloy, on the other hand, possesses a high silicon content (usually about 12-14%), making it harder, which means that it won’t plasticize as readily as 2618. As a result, pistons made from 4032 need to be thicker and heavier to provide the needed strength. However, the higher silicon content provides a harder wear surface, and subsequently longer piston life. According to Chris, 4032 is a good choice for naturally aspirated street applications (and for relatively lower turbo boost pressures), while 2618 is a better choice for higher boost pressures (16 lbs or more). Top Fuel applications, where extremely high cylinder pressures are a constant, 2618 is the common material of choice. While 2618 alloy provides outstanding high-temperature characteristics, greater wall clearance is usually required due to this material’s tendency to expand and contract.
Dave Calvert at CP Pistons notes that although 4032 aluminum can be an acceptable choice for street and some supercharged applications, the majority of their pistons are manufactured from 2618 forgings, since this grade of very pure and strong aluminum allows precise thermal growth calculations, allowing engineers to accurately predict piston dimensional changes during anticipated cycling operation in any given engine and its track application.
The many technology changes in pistons over the previous five years or so involve increasing piston strength and resistance to fatigue. An example, according to CP’s Dave Calvert, is use of the “box style” (also called strutted) pin boss design to increase rigidity. These reinforcing struts stabilize the pin bosses and the ring grooves, adding dramatically superior strength around the piston periphery.

CNC machining offers precise and repeatable dome configurations.

Top ring grooves are typically hard-anodized to prevent microwelding.

We spoke with Barry Rabotnick, the chief tech honcho at Federal Mogul regarding that firm’s current developments. Barry noted that they’ve recently introduced a new line of high-performance/race entry-level forged pistons that offer big-time benefits at a street-level price. The new line features lighter weight and shorter skirts, with a webbed reinforcement underside. The pin boss area has been shortened up, and cut-throughs are machined into the webbing for quick oil drainback. A notable feature involves a “figure eight” skirt configuration that is slightly larger on the thrust side (a very sophisticated skirt design, made possible via 3-D computer modeling and CNC processing). Further taking advantage of CNC processing, all domes are CNC cut as well.
Ring placement has moved higher, with an accumulator groove featured between the top and second ring locations, which increases the volume of the area between the rings. As Barry explained, when a tight ring package is used, this accumulator groove prevents inter-ring pressure buildup, allowing both top and second rings to function properly. All ring lands are CNC-machined, and a 0.010″ radius is featured at the root of the top and second grooves (instead of a square cut), which increases material strength.
All of these new pistons also feature a silk-screen-applied Duroshield coating (moly graphite with polymer mix, which serves as an anti-friction/scuff coating), as well as lightweight tapered pins.
According to Probe’s Chris Huff, moving the rings higher produces several results, including a reduction in emissions (naturally a concern for the OE side). In racing applications, the top ring seals better when it’s closer to the top. This is good for drag or circle track applications, but if nitrous or a blower is involved, the downside is greater concern for blowing the top ring lands off. In turbo applications, for example, the rings need to move further away from the top to get away from the excess combustion heat and pressure.
Hard anodizing on the top ring groove is a solid move for high combustion temperature situations (turbo, etc.) and in some endurance NASCAR applications to prevent microwelding. However, notes Huff, “ring groove hard anodizing isn’t something we see much in the sportsman realm.”
In terms of piston compression height, according to Huff, “we’re increasingly seeing this in stroker builds where longer rods are being used, with compression heights moving well beyond the once-considered limits of 1.5 – 1.75″, to compression heights in some applications reaching the 1.2 – 1.3″ range.”
Huff also noted that in some cases, pins are moving up far enough that they intersect the oil ring groove. Huff’s advice is to stay away from this on a street engine. Instead, a slightly shorter rod coupled with an offset pin bore in the piston is a better route to take to reduce rod angle, rattle and load on the cylinder wall.
Gas porting (strategically-located holes drilled from the dome perimeter into the top ring groove) applies pressure directly to the rear ring face, basically eliminating side clearance, which prevents ring flutter during high-RPM operation. This works best with thin, narrow top rings (i.e. 0.043″ thick) and short piston compression height. However, since the positive pressure effects of gas porting tends to greatly reduce top ring life, this feature is applicable only to routinely-serviced race-only engines, and is never a good idea for a street motor.

COMPRESSION RATIO FORMULAS

FORMULA ABBREVIATIONS

GV………..gasket volume
DV………..below deck volume
HV………..head chamber volume
VV………..dish, valve pocket, dome volume
(minus for dish or pockets; plus for dome)
PV…………volume displaced by piston
GV = Bore (in) x Bore (in) x 12.87 x head gasket thickness
DV = Bore (in) x Bore (in) x 12.87 x inches below deck
HV = CCs
VV = CCs
PV = Bore (in) x Bore (in) x Stroke (in) x 12.87
Compression ratio = GV + DV + HV – VV + PV
Divided by GV + DV + HV – VV

Cubic inches = Bore x Bore x Stroke x no. of cyls x 0.7854

To convert cubic inches to CCs……..Cubic inches x 16.386
To convert cubic inches to liters…….Cubic inches x 0.016386

To convert CCs to cubic inches……..CCs divided by 16.386
To convert Liters to cubic inches……Liters divided by 0.016386

Engine in Liters = Bore (mm) x Bore (mm) x stroke (mm) x no.
of cyls x 12.87,
Divided by 16386 x 1000

Engine in CCs = Bore (mm) x Bore (mm) x Stroke (mm) x no.
of cyls x 12.87,
Divided by 16386

Mahle Motorsports’ Trey McFarland noted that among the many features in their forged performance and racing piston designs are shorter pins, which enables opening up the sides of the pistons to obtain both lighter weight as well as reducing overall drag. Pin bosses are moved further inboard to work with the shorter pins. This removes flex from the pins, placing the stresses back into the piston, which allows designers to build-in the degree of strength and rigidity that’s needed to best control piston growth.
Trey also noted that all Mahle forged pistons are dip-coated with a dry film phosphate coating. The intent of this coating (a proprietary material Mahle calls Grafal) is multi-faceted. This coating maintains consistency of tolerances in the ring grooves and provides added anti-galling protection in the pin bores. Since this coating is applied to the entire piston, it prevents any potential for microwelding inside the grooves. Another very notable benefit is provided by the coating’s compressible membrane, which “cushions” the piston skirt areas. This extends piston life, generates less noise (important for fuel-injected engines that use knock sensors) and reduces piston inertia as the piston rocks, which in turn reduces shock loads and harmonics that would otherwise be transmitted to the rods and bearings.
In terms of weight reduction and increased strength, Mahle’s “box in box” underside webbing structure works in conjunction with the narrower pin bosses to increase rigidity. Trey noted that this design is sometimes not feasible in applications that use aluminum rods, as these thicker rods may not provide adequate room for this design.
Another feature involves back-cutting the ring lands between the second and third ring grooves, which allows scraped oil to more quickly and efficiently be brought down to the oil ring package for superior oil control.

PISTON COATINGS

Once considered a “snake oil” treatment (in reality, nothing could be further from the truth), skirt coatings have now become accepted and commonplace. This generally involves an application of moly graphite (or similar material) to the skirt surfaces. This slick coating, especially when exposed to engine oil, offers a super-slick contact area for those occasions when the skirt touches the cylinder wall (cold starts, transitional rocking at top and bottom centers). This virtually eliminates skirt scuffing, saving both the skirts and the bore surfaces. The film buildup involved in this coating is so minimal that no honing compensation is required in terms of finished bore diameter.

Dome coatings consist of thermal-barrier ceramic applications. Shown here is a ceramic coating by Swain.

Moly graphite skirt coatings offer anti-scuff protection, providing insurance against potential damage during cold starts and piton rock. Thermal dome and moly skirt coatings shown here are from Polydyne.

Thermal barrier coatings (applied to the piston dome) are generally ceramic-based materials, which serves two purposes: since the coating reflects heat (acting as a heat barrier), a much greater percentage of combustion heat is maintained in the chamber for a more efficient burn. This coating also minimizes piston thermal expansion, since less heat is transferred into the piston body. This allows greater control of, or more even, thermal expansion, theoretically permitting the use of tighter piston-to-wall clearance. These coatings, available in a variety of “grades,” are especially suited to turbocharged applications, since some of these ceramic coatings can withstand approximately 2,100 degrees F exposure.
It’s important to note that by their nature, these hard ceramic coatings MUST be applied properly. If surface prep and curing is not executed properly, this material can flake off, which will result in severe cylinder wall and bearing damage. This is why it’s critical to have these coatings applied only by an experienced and skilled coating application shop that specializes in these treatments. In other words, don’t try this at home.
While not a coating, a hard-anodizing treatment inside the top ring groove has also gained acceptance in applications where ring micro-welding is a concern.

Sources

Dial 1-800-652-0406 and then the Quik-Link
number after a company to reach them directly!
www.precisionenginemag.com

PISTON MANUFACTURERS

Arias Pistons
13420 S. Normandie Ave.
Gardena, CA 90249-2212
Quik-Link #11054

CP Pistons
1902 McGraw
Irvine, CA 92614
Quik-Link #11055

Diamond Racing Products
23003 Diamond Dr.
Clinton Twp., MI 48035
Quik-Link #11056

Federal-Mogul Performance
26555 Northwestern Hwy
Southfield, MI 48034
Quik-Link #11057

JE Pistons, Inc.
15312 Connector Lane
Huntington Beach, CA 92649
Quik-Link #11058

KB Performance Pistons
4909 Goni Rd.
Carson City, NV 89706-0351
Quik-Link #11059

Mahle Motorsports
270 Rutledge Rd. Unit B
Fletcher, NC 28732
Quik-Link #11060

Probe Racing Components
2555 West 237th St.
Torrance, CA 90505
Quik-Link #11061

Ross Racing Pistons
625 S. Douglas St.
El Segundo, CA 90245-4812
Quik-Link #11062

Wiseco Piston Co.
7201 Industrial Park Blvd.
Mentor, OH 44060
Quik-Link #11063

Dart 11-Degree Big Chief Cylinder Head Specs
P/N………………………18500000
Material…………………355T6 aluminum alloy
Comb. Chambers……….56cc (70cc also available)
Intake valve dia…………2.470″
Intake port dim. …………1.815″ x 2.725″ w/3/4″ radius
Intake port volume………FP CNC – 497cc
Intake port location……..Raised 1.500″ spread ports
Exhaust valve dia………1.800″
Exhaust port volume……185cc
Exhaust port dim………..2.020″w x 1.780″h
Exhaust port location……angled & raised 0.900″ extended flange w/BBC bolt pattern
Intake flow………………520cfm @ 0.900″ lift/28″
SuperFlow 1020/+20cfm on SuperFlow 600
Exhaust flow…………….355cfm @ 0.900″ lift/28″
Lifter……………………..Use 0.180″ offset lifter
Manifold…………………Dart Big Chief Oval 1×4 bbl = 8″ tall
Milling…………………..56cc = 0.145″ (70cc = 0.080″)
Pistons…………………..Must use pistons for Big Chief head
Retainers………………..Titanium 10-deg
Spark plug………………0.750″ reach, gasketed Autolite AR3932
Spring cups……………..1.625″ – 0.060″ cup
Spring pockets………….1.740″ OD for 1.625″ cup (0.030″ deeper max)
Springs………………….Dart 1.625T = 330# @ 2.100″ / 0.910″ max Comp 948
Valve angles…………….Intake 11 deg x 6 deg Exhaust 7 deg x 4 deg
Valve length…………….Intake 6.600″ Exhaust 6.450″ (for 2.150″ installed height)
Valve stem dia…………..0.3415″ (11/32″) (5/16″ optional)
Valve train………………Jesel or T&D 11-deg rocker system
Valve guides…………….1/2″ OD Mag-bronze Cut for 0.500″ PC seals (0.002″ press)
Valve guide length………3.000″
Valve guide clearance……0.0014″ – 0.0021″ (with 0.3415″ dia. valve stem)
Valve guide spacing………widened for use on min. 4.600″ bore
Valve seats……………….Copper-Berylium, 0.008″ press
Valve seat dim. ………….Int 2.520″ x 2.00″ x 0.375″ Exh 2.000″ x 1.560″ x 0.375″
Valve seat angles……….. 55 deg
Head studs……………….ARP # 235-4312 (or Dart kit # 66120015)
Titanium valves………….Must use lash caps
Torque w/oil……………..Head bolts = 70 ft-lb
(Dart’s inner head studs 3/8″-7/16″ = 50 ft-lb
Manifold = 35 ft-lb
Block application………..Dart Big M, Mark IV, Gen V, Gen VI with proper head gasket
Cyl. Head weight………..42 lbs

The 0.5201 intake cam lift, when mated to our Jesel 1.85:1 rockers, will achieve an effective valve lift of about 0.962″. Lobe ramp angles are very shallow (to the eye, they look straight), so this pup should provide quite a rumpety-rump attitude.

Our roller lifters and valve springs were specially selected by Crane to suit our specific build.

This closeup shows the 0.180″ offset pushrod cup for the intake lifters, necessary for the Big Chief II 11-degree heads.

Our rocker system is a shaft roller setup from Jesel, featuring a hefty 1.85:1 ratio. Along with our custom Crane cam, this will provide nearly an inch of effective valve lift. Woof.

Our head gasket choice are MLS units from Victor.

Tri-Armor main and rod bearings from Clevite will create the necessary oil film to support our crank and rods. This is Clevite’s new line of coated bearings. The coating applied by Clevite is a proprietary polymer-based compound.

The Moroso billet gerotor style oil pump is a kick-ass unit with a built-in pickup screen, so there’s no worry about vibrating or cracking a pickup tube.

Here’s a closeup of the oil pump’s built-in pickup screen.

We opted for a Jesel belt drive for precision cam rotation.

We selected an 8″ ATI Super Damper to jive with our MSD flying magnet ignition system.

The Moroso wet sump aluminum oil pan is a recent addition to their line. The pan rail configuration requires extra tapped holes in the block’s rails.

Threaded plugs in the pan allow driver access to the center rail fasteners.

Moroso sheet metal aluminum valve covers will adorn the Dart Big Chief II heads.

The MSD Pro Billet distributor features a length that will accommodate the Dart tall-deck block.

The MSD flying magnet crank trigger will provide accurate ignition timing (this requires the use of an 8″ damper).

MSD Super Conductor plug wires are 8.5mm thick for carrying ample juice to this radical pup.

In order to take advantage of maximum coolant flow, and to eliminate the need for a water pump belt, we chose an electric pump from Meziere. This unit features a chrome finish, but black (and other colors) is also available.

Our giant-gulp carb is Holley’s 1150 cfm Dominator. This will be used if we opt for a single-carb intake manifold.

Depending on our intake manifold choice, we may run a pair of 1050s.

ARP threaded fasteners will be used throughout to anchor everything together. We opted for head studs instead of bolts.

Product Support
Thanks to the following for their involvement in this project…

Dial 1-800-652-0406 and then the Quik-Link number after a company to reach them directly!
www.precisionenginemag.com

ARP INC.
1863 Eastman Ave.
Ventura, CA 93003
Quik-Link #11064

ATI PERFORMANCE
PRODUCTS
6747 Whitestone Rd.
Baltimore, MD 21207
Quik-Link #11065

CLEVITE ENGINE PARTS
1350 Eisenhower Place
Ann Arbor, MI 48108-3282
Quik-Link #11066

CRANE CAMS, INC.
530 Fentress Blvd.
Daytona Beach,FL
32114-1200
Quik-Link #11067

DART MACHINERY
353 Oliver St.
Troy, MI 48084
Quik-Link #11068

DIAMOND RACING
PRODUCTS
23003 Diamond Dr.
Clinton Twp, MI 48035
Quik-Link #11056
HOLLEY PERFORMANCE PRODUCTS
1801 Russellville Rd.
Bowling Green, KY 42101
Quik-Link #11069

JESEL VALVETRAIN INC.
1985 Cedarbridge Ave.
Lakewood, NJ 08701
Quik-Link #11070

LUNATI
(see Holley Performance Products)
Quik-Link #11071

MAHLE MOTORSPORTS
270 Rutledge Rd., Unit B
Fletcher, NC 28732
Quik-Link #11060

MOROSO PERFORMANCE PRODUCTS
80 Carter Dr.
Guilford, CT 06437
Quik-Link #11072

MSD IGNITION
1490 Henry Brennan Dr.
El Paso, TX 79936-6805
Quik-Link #11073

DART RACE SERIES BLOCK
Dart’s new monster big block offers a choice between 10.600″ or 11.100″ deck heights, a cam tunnel that’s moved up 0.600″ for better connecting rod clearance with stroker cranks and a choice between 4.840″ or 4.900″ bore spacing. The new tall-deck block offers engine builders great versatility with variable lifter locations and provisions for symmetrical or siamesed-port cylinder heads.
OIL PUMP & PAN
To avoid pump pickup cracking (due to engine shake), we opted for a very beefy billet gerotor style oil pump from Moroso, their P/N 22167. This pump features a built-in pickup incorporated into the bottom of the billet pump body, so there’s no external pickup to vibrate loose. The matching oil pan to accommodate the Dart block and this pump is Moroso’s billet 2-piece aluminum pan, P/N 20376.
CAMSHAFT SPECS
Crane was kind enough to machine a custom-grind steel billet solid-roller stick for us. This is P/N 13R001027, Grind number R-288/5201-2S-14 SFO (Special Firing Order). Effective lift (with our raunchy 1.85:1 rocker ratio) is almost a full inch…woof!
LIFT
@ cam….. 0.5201″ intake; 0.5001″ exhaust
(with our 1.85:1 rocker ratio from Jesel, valve lift should be 0.962″ intake and 0.925″ exhaust. If used with 1.70:1 rockers, valve lift would be 0.884″ intake and 0.850″ exhaust)

ADV. DURATION
317.0 deg. intake; 356.0 deg. exhaust
VALVE SETTING (hot)
Intake 0.020″; Exhaust 0.022″
CAM TIMING (@ 0.020″ tappet lift)
Intake opens 49.5 deg. BTDC; closes 87.5 deg. ABDC
Exhaust opens 113.0 deg. BBDC; closes 63.0 deg. ATDC
CAM TIMING (@ 0.050″ tappet lift)
Intake opens 35.0 deg. BTDC; closes 73.0 deg. ABDC
Exhaust opens 96.0 deg. BBDC; closes 38.0 deg. ATDC
Duration: Intake 288.0; exhaust 314.0
VALVE SPRINGS (P/N 96849 triples)
Closed 352 lbs @ 2.200″
Open 928 lbs @ 1.370″
(minimum RPM 4700; maximum RPM 8700; valve float 9300 RPM)
NOTE: This is a special firing order (SFO) camshaft.
Firing order is 1-8-7-3-6-5-4-2
As usual, we’ll provide plenty of detailed information relative to all of the components as well as all machining and assembly info in the next article.
As I mentioned earlier, Diamond is making our forged pistons (they have plenty of experience in designing slugs for 632 builds, so this’ll work out peachy). In the next issue, I’ll provide all of the custom piston specifications.
As soon as Eric Simone of Diamond Racing finishes our pistons, we’ll hone-fit the cylinders and file-fit our Perfect Circle rings. At that point, we’ll fit-check our crank and rods for clearance. Once that’s done, we’ll balance the crank, rods and pistons and begin our trial-fit, degreeing the cam and measuring for pushrod length. We expect to perform a host of fitting procedures, including fine-fitting and port-matching our intake manifold-to-head fit, checking pushrod clearance and correcting as needed, etc.
Oh, by the way, we plan to use a new digital cam degreeing system from Cam Logic, which we’ll feature in depth. I saw this at the recent PRI show in Orlando, and it made my mouth water (I wanted to use a different analogy, but I need to watch my language). I can’t wait to try it out.
While we won’t pursue a perfect smooth exterior block finish (remember our recent 383 Dart smallblock Chevy streetrod build?), we’ll nonetheless tidy up the block exterior for enhanced appearance, eliminating any casting flash. We haven’t decided on a block color yet, but I think we’ll stay away from black, mainly because it’s difficult to photograph (black hides too many details).
Once our mutant baby is final-assembled, we’ll trek up to Koffell’s Place in Huron, Ohio for the dyno run, using Scott’s DTS engine dyno. If all goes well, we should be able to comfortably nudge around 1200 HP out of this big-gulper.

Our Dart Big M block features a 10.2″ deck height (9.8″ deck is also available). Camshaft bore position matches standard big block Chevy.

Bores are slightly undersized, providing plenty of meat to hog out to achieve our 4.600″ desired diameter. Minimum cylinder wall thickness is 0.300″.

The steel billet main caps feature splayed outer bolts on #2, 3 and 4 (all caps are 4-bolt), and feature deep-stepped registers on each side. The main bearing bore measures 2.937-2.938″, accepting standard big block Chevy main bearings.

Lifter bore diameters measure 0.8427-0.8437″, accepting +0.300″ longer roller lifters.

Each valley side of the block features two slotted bosses to accommodate the four head bolts that are installed on the underside of the heads.

Clearance reliefs are already provided at the bottom of the bores. Depending on the stroke, additional clearancing may be required. We’ll test-fit our 4.750″ stroker crank to verify.

The Dart Big Chief II alloy heads are, well, big. This is a hefty 42-lb chunk of 355T6 aluminum.

Intake flow is rated at 520 cfm @ 0.900″ lift at 28 inches on a SuperFlow 600 test bench. Intake port volume is 497cc.

Our heads feature 56cc chambers (70cc also available). Intake valve diameter is a whopping 2.470″, and exhaust valves are 1.800″. The heads came equipped with Victory titanium valves.

Intake ports are 2.725″ x 1.815″ and feature a 3/4″ radius.

Exhaust ports (as intakes) are CNC machined. Notice the beautiful blend radius at the valve boss.

This says it all.

Our crank is a steel unit from Lunati, with 4.75″ stroke.

That’s a hefty stroke in anybody’s language.

Our rods are Lunati Pro Billet I-beam connecting rods, P/N LB01.

The Lunati rods feature a center to center length of 6.700″.

The matching Crane set includes cam, offset roller lifters, springs, retainers and locks.

Our bumpstick is a steel billet cutie from Crane. We’re also using their solid roller lifters (offset to work with the Dart heads), titanium keepers and retainers, and big-ass springs (rated for float at 9300 RPM).

We build a big, big block drag mill

just for the sheer hell of it.

by Mike Mavrigian

photos by author

Some folks love to claim that bigger is not always better. While that may be true in some cases, let’s face it…when the conversation turns to displacement, well, bigger cain’t never hurt. After all, if you feed any block huge doses of Viagra, rest assured that you’ll be able to sit back and enjoy the show.
We’ve talked to a few builders who have produced 632 CID all-motor drag engines, and generally speaking, they’re popping around 1,200+ HP out of these big-breathers. So, we figured we might as well build one and provide our readers with all of the pertinent details. Sure, there are larger-cube mills out there, but the popular 632 sounds like a neat build, so that’s what we chose.
The basis of our build will begin with a stout no-nonsense Dart “Big M” iron block that features a 10.2″ deck height. We’ll hog the bores to 4.600″, and mate this to a whopping 4.75″ stroker crank from Lunati. We plan compression on the tight-squeeze side, at about 15:1. No laughing gas or added air-squeeze for this bad boy…it’s gonna pop, dig in it’s hoofs, and bellow and scream by simply igniting the fuel and air fed through either a single 1150 cfm Holley Dominator or a pair of Dominator 1050 carbs, depending on our intake manifold of choice. We’ll mechanically feed fuel to the carbs via -8 plumbing.
We’ve gathered most of the parts needed with the exception of the forged & CNC-cut pistons, which are being custom made by Diamond Racing Products. We discussed our piston specs with Diamond’s Eric Simone, who was a tremendous help in determining the piston configurations based on our specific build. Piston rings are coming from Clevite/Perfect Circle. Top rings will be ductile iron with plasma face, with an axial height of 0.043″ and radial width of 0.170″. Second rings will be gray iron THG with axial height of 0.043″ and radial width of 0.210″. These rings will be file-to-fit. The oil ring package will feature an axial height of 3mm and a radial package width of 0.146″.
Once we perform our initial test-assembly, we’ll order a set of custom-length pushrods (likely 7/16″ diameter). We thought our readers would be interested in reviewing our plans to date. This build should be both informative and fun (hey…fun is always good).

Our Parts List
BLOCK………………………….Dart Big M with 10.2″ deck height
CYLINDER HEADS……………Dart Big Chief II 11-degree with 56cc chambers
CRANKSHAFT…………………Forged 4.75″ stroker from Lunati, P/N BS-421 MN
(counterweight radius @ 3.700″)
CONNECTING RODS………….Forged I-beam Pro Mod 6.700″ Lunati, P/N LB01
CAMSHAFT…………………….Custom billet steel mechanical roller from Crane,
P/N13-R001027; grind no. R-288/5201-2S-14 SFO
LIFTERS…………………………Crane offset solid roller Ultra Pro R/T rollers P/N 13571-16
RETAINERS/KEEPERS………..Crane titanium set P/N 99681-16
VALVE SPRINGS………………Crane triple spring set P/N 96848-16
MAIN BEARINGS………………Clevite Tri-Armor P/N MS-829 HXK
ROD BEARINGS………………..Clevite Tri-Armor P/N CB-743 HXK
OIL PUMP……………………….Moroso billet gerotor P/N 22167
OIL PAN…………………………Moroso 2-pc welded billet aluminum, P/N 20376

CARBURETOR…………………Holley Ultra Dominator 1150 cfm, P/N 0-80673
INTAKE MANIFOLD…………..Profiler tunnel ram
TIMING/COVER………………..Jesel belt drive kit KBD-32000

VALVE COVERS……………….Moroso welded aluminum P/N 68334
ROCKER ASSEMBLIES………..Jesel shaft roller rocker system P/N KPS 24347
(1.85:1 int & exh)
PUSHRODS………………………TBA
PISTONS…………………………Diamond Racing
DISTRIBUTOR…………………..MSD billet, P/N 8558 (tall block)
CRANK TRIGGER………………MSD flying magnet kit P/N 8620
DIST. CLAMP……………………MSD P/N 8110
SPARK PLUG WIRES……………MSD 8.5mm Super Conductor P/N 31239
WATER PUMP……………………Mezier WP300
EXHAUST HEADERS……………TBA
DAMPER………………………….ATI 8″ Super Damper P/N 917062
CYL. HEAD GASKETS…………..Victor MLS P/N 54271
VALVE COVER GASKETS………Victor VS50191HTC
THERM. HOUSING GASKET…….Victor (alum. W/silicone seal) P/N C21331
REAR MAIN SEAL………………..Victor 2-pc P/N JV705
EXH. GASKETS……………………Victor Nitroseal Pro-Stock P/N 95178SG
FASTENERS……………………….ARP
Head studs # 235-4312
Header studs # 400-1403
Oil pan studs # 435-1901
Balancer bolt # 235-2501
Carb stud kit #400-2414
Intake manifold bolt kit # 435-2101
Timing cover bolt kit #400-1501
Thermostat housing bolt kit # 430-7401
Flexplate bolt kit # 200-2902
Valve cover stud kit # 400-7615
Distributor stud kit # 430-1701
Water pump bolt kit # 430-3201
ARP moly assembly lube # 100-9906

DART BIG M BLOCK SPECS
Part No. ……………….31263344 through 31273454
Material…………………superior iron alloy
Bore…………………….4.250″ and 4.500″
Bore & stroke…………..4.625″ x 4.750″ max recommended
Cubic inch………………632 CID max recommended
Cam bearing bore ID……2.1195″ – 2.1205″
Cam bearings……………Special coated, grooved, w/ 3 oil holes
Cam bearing O/S………..+0.010″, +0.020″, +0.030″
Cam bearing press………0.002″
Camshaft position………standard BBC
Cam drive………………standard timing chain, gear drive or belt drive
Cam plug……………….standard BBC 2.218″ dia.
Cylinder wall thickness…0.300″ minimum @ 4.625″ bore
Deck height……………..9.800″ & 10.200″
Deck thickness………….adequate for all applications
Fuel pump………………mechanical pump provision
Fuel pump pushrod……..standard BBC
Freeze plugs…………….press-in cup plugs
Head gasket…………….Fel-Pro #1037, 1047 or 1067
Inner head stud………….2 slotted bosses per side
Lifter bores……………..BBC 0.8427″ – 0.8437″
Lifter galley……………..raised 0.350″ for longer lifter bore
Lifter type………………roller Gen VI (+0.300″ longer), solid Mark IV
Main bearing size………standard BBC
Main bearing bore………2.937″ – 2.938″
Main caps……………….steel billet or ductile iron (sportsman); all 4-bolt
Main cap register……….deep-stepped register on each side (no need for dowels)
Main cap press………….0.005″
Main cap bolts…………..all 1/2″ (#2, 3, 4 have splayed outer bolts)
Oil system……………….wet or dry sump, main priority oiling
Oil galley, main………….stepped, 9/16″ – 1/2″ – 7/16″
Oil galley, filter main……5/8″
Oil filter………………….stock oil filter location
Oil pan……………………standard pan bolt pattern,
extra bolt holes provided for strokers
Rear main seal……………standard 2-pc seal / Fel-Pro #2918
Rear main thrust width…… 1.622″ – 1.624″
Serial number……………..on main caps
Starter……………………..mounts in standard location
Stud holes, head……………blind holes
Timing chain/gears………..standard BBC
Timing cover………………standard BBC
Torque specs………………all 1/2″ bolts @ 100 ft-lbs
Weight……………………..4.250″ bore = 280 lbs
4.500″ bore = 260 lbs
4.600″ bore = 250 lbs

HANDY ASSEMBLY TOOL
While I’m on the subject, here’s a very cool specialty tool that eases the pain of hose assembly. I just came across this tool recently, and I like it. It’s called the Koul Tool (aptly named). While you don’t absolutely need this tool, if you want to save your fingertips from needle punctures from frayed stainless-steel wire, I’d highly recommend it.
The tool is essentially a guide that allows you to feed the hose onto the hose end’s collar, while encapsulating the sharp tips of the wire braid.
The tool is offered in kit form, to cover all popular hose sizes. Kit P/N 468 covers sizes -4, -6 and -8; while Kit P/N 1016 covers hose sizes -10, -12 and -16.
Here’s how it works: Choose the correct-size tool for the hose end to be installed. The tool is made of two pieces that clam-shell together. Place the hose end collar in one side of the tool, enclose it with the mating side, secure the tool in a vise, lube the funnel entrance and install the hose using a twisting motion. The tool’s funnel entrance guides the hose neatly into the collar with no muss or fuss.
In fact, while the hose end cap is still in the clamshell, with the hose inserted, you can leave the tool in the vise and install the remainder of the hose end, threading it into the collar while the collar is held stationary.
The kits include several adapters, since the various hose end and fitting makers often produce their own unique lengths. The kit instructions advise you regarding the need for adapter spacers. For instance, the kit’s #1 adapter is required for Aeroquip -16, while -16 Fragola, Goodridge, Earls and XRP hose ends require the kit’s #2 adapter. The hose end must fit inside the tool tightly, with no end-play. The adapters simply serve as spacers to prevent the hose end from walking inside the tool.

These are the hose-end installation tools from Koul Tool. Two kits are available. The kit on the left handles sizes -4, -6 and -8, while the kit on the right handles sizes -10, -12 and -16.

Simply place the hose end collar into one half of the clamshell tool, with the hose entry port facing the tool’s funnel end.

Assemble the two clamshell halves together.

Lube the funnel port, and insert the braided hose, “screwing” the hose into the tool in a clockwise movement. You’ll feel the hose stop against the collar threads.

With one half of the clamshell removed, you can see the hose installed into the collar. This is a very “slick” (pun intended) way to install a braided hose into a collar.
Note: because some maker’s hose end collars vary in length, the Koul Tool kits include plastic spacers and instructions regarding the need for a spacer (and spacer size), depending on the specific brand of hose end being assembled. If a spacer is needed, it is positioned between the collar’s threaded port (the hex side) and the inside of the tool. If a certain hose-end maker’s collar is on the short side, as it is pushed back into the tool during hose insertion, the hose entry port might move back behind the funnel port, possibly allowing the hose braid to expand. The object is to place the hose end collar’s hose port directly at the base of the tool’s funnel. This isn’t difficult. The tool instructions clearly tell you when a spacer is needed, so there’s no need for you to figure anything out. Here we used an Aeroquip -10 hose end collar, where no spacer was required.

As long as the hose and collar are in the tool, you can take advantage of this and insert the hose end socket/nipple. Here, we removed the hose and tool from the vise and flipped it 180 degrees to expose the collar’s threaded port. Remember to lube the nipple and threads.

Here we tighten the hose end assembly using an aluminum -AN wrench.

Each Koul Tool is clearly marked for -AN size.

Even for seasoned racers who have assembled countless numbers of -AN hose ends, this little tool is, well, way cool. It’s like using a good shoehorn. It definitely saves your fingers.

PROTECT THE HOSE ENDS AND
FITTINGS
Whenever you’re dealing with aluminum hose ends and fittings, be aware of two precautions: aluminum is softer than steel, so your steel tools can gouge or burr these items. Also, if you’re concerned about appearance (street rod, custom application, etc.), you certainly don’t want to burnish off the attractive anodized finish. Instead of taping a wrench or trying to jam a piece of cloth between the fitting and a wrench, make the investment and buy a selection of aluminum -AN wrenches. The aluminum wrenches, unless they’re dirty and gritty, won’t damage your pretty hose ends or fittings.
Also, be aware that an anodized component’s finish can be damaged by aggressive solvents. You can damage the coloration by using some brake cleaner solvents or thinners. However, some anodized items feature a protective clear anodizing treatment over the color-dyed treatment that helps to protect the appearance. Regardless, don’t take chances. Use only a mild cleaner, and never use any cleaner that contains abrasives (such as buffing compound).

If you care about preserving the appearance of your aluminum hose ends and fittings, invest in a set (or two) of aluminum AN wrenches. The set shown here is from Gearhead Tools, but this type of wrench is readily available from most of the hose/hose end makers. Believe me, you need these tools!

Even when using an aluminum AN wrench, make sure that the surfaces are clean to prevent scratches that could result from grit. Here we install hose assemblies onto a race engine’s dry sump pump.

AN wrenches are clearly marked for the intended AN size, plus they’re usually color-coded per size to make it easy to identify them. Notice the small radiused cutouts at the corners on this wrench, which prevents corner-edge contact. If a bit of dirt has accumulated in the corners, these cutouts help keep grit away from the hose end.

Although aluminum AN wrenches are designed for this dedicated task, bear in mind that not all hose end and fitting hex dimensions are created equal, as some hose end and fitting manufacturers’ hex dimensions may differ. However, these wrenches will fit the vast majority of applications as intended. The fit of this -12 wrench on this XRP -12 hose end is perfect.

Stainless braided hose and AN hardware provides worry-free hose life (don’t need to worry about a hose leaking due to a rub-through) and reliable connections, since the 37-degree AN seating creates a surefire fluid seal.

Considering the many possible combinations of hose end and fitting angle shapes available, it’s easy to obtain exactly the routing that best suits your needs and visual tastes.

SLIP-ON BARBED NIPPLE AN
If you opt to use AN hose ends with barbed nipples and the proper reinforced hose designed for these hose ends, in theory the task is easy. Simply insert the barbed nipple tube into the hose until the end of the hose seats into the shallow stop-collar. However, this is anything but easy, due to the tight interference fit of the nipple in the hose. Lube the nipple with WD40 or lithium grease, and push the hose onto the nipple. You’ll need your strength for this. I’ve found that it helps to first dip the end of the hose into very hot water (to slightly soften and expand the hose). Once the hose is fully inserted, it’s not coming off.

Reinforced hose designed for use with barbed nipple hose ends. This is tough stuff. You’ll need a very sharp razor to cut this.

Shown here is a 90-degree barbed-nipple AN hose end. The two barbs provide an extremely secure retainment to the hose.

Here the hose is pushed onto the nipple about halfway. Keep working with it until the end of the hose seats fully into the shallow stop-collar.

QUICK-DISCONNECTS
Quick-connect/disconnect fittings are available that allow you to quickly (with no tools) disconnect or connect fluid hose assemblies with no fluid loss. Jiffy-Tite (probably the most popular of this genre) offers self-sealing connectors suitable for fuel, oil and water applications. The coupler features a spring-loaded valve that shuts off when the coupler is disconnected, and opens when connected. This is perfect for race cars, where engines are serviced or changed on a regular basis, since this quick-connect feature saves time. Simply slide the coupler collar back to release the connection. You can pop the couplers loose and yank an engine without spilling fluids. Even though these couplers are easy to disconnect and reconnect by hand, once coupled, the connection is secure with no worries about accidental disconnection or leakage.
These self-sealing fittings are available in a variety of thread styles including AN, NPT pipe thread, reusable hose ends and barb type hose ends. Every imaginable configuration is also available (male/male, male/female, female/female, etc.).

Straight hose end (left) with self-sealing quick-disconnect coupler. This connects to the coupler fitting (right), which in turn features a male -AN flare. Photo courtesy Jiffy-Tite

Special quick-connect carburetor adapters are available (installed at the carb bowl as seen here) that accept the quick-connect hose end. This allows you to pull the spring-loaded coupler back, and disconnect the fuel line from the carb with no fuel loss, since the hose end seals itself when uncoupled. Photo courtesy Jiffy-Tite

This dry sump oil system connects to its remote oil reservoir using a Jiffy-Tite quick-connect hose end coupler. This particular engine is on a display stand, but in a race car, this allows you to quickly disconnect the oil hoses without spilling oil. As soon as the coupler is disconnected, a spring-loaded valve shuts and seals.

This quick-connect coupler features a male -AN (where it mates to the 90-degree hose end).

Jiffy-Tite offers a wide range of configurations. Pictured here is a 45-degree hose end that features the self-sealing quick-connect coupler. Photo courtesy Jiffy-Tite

Pictured here is a 90-degree quick-connect hose end. Photo courtesy Jiffy-Tite

-AN TUBING
-AN plumbing can also be handled using hard-line tubing. -AN flare-seat connections are made using tube sleeves and tube nuts. We don’t have room in this article to address tubing in detail, so we’ll try to present a separate article in tubing in a future issue.

This custom Chevy smallblock, intended for a street rod build, is adorned with hard-line fuel plumbing. I had a specific theme in mind when I built this engine, and decided that hard lines would look nifty. I sent all of the aluminum tube nuts, tube sleeves and AN adapters to a custom anodizing shop where they were stripped of their original blue color and re-anodized in a dark violet color to contrast with the lavender metallic engine color. We hand-polished the 3/8″ aluminum tubing.

This hard-tube plumbing setup on a Honda engine shows what can be done with a simple hand-held tubing bender and a little bit of patience.

Sources
Dial 1-800-652-0406 and then the Quik-Link number after a company to reach them directly!
www.precisionenginemag.com

-AN PLUMBING HOSE, HARDWARE & TOOL MANUFACTURERS
A-1 PERFORMANCE PLUMBING
(reinforced hose, hose ends, fittings)
1927-2 Stout Dr.
Warminster, PA 18974
Quik-Link #11074

AEROQUIP PERFORMANCE PRODUCTS-EATON
(reinforced hose, hose ends, fittings, adapters)
14615 Lone Oak Rd.
Eden Prairie, MN 55344
Quik-Link #11075

BMRS
(reinforced hose, hose ends, fittings, adapters)
Concord, NC
Quik-Link #11076

BRAKEQUIP
(braided brake hose assemblies)
1470 Amherst Rd.
Knoxville, TN 37909
Quik-Link #11077

EARLS PERFORMANCE PLUMBING (div. Holley)
(reinforced hose, hose ends, fittings, adapters, coolers)
Holley Performance Products
P.O. Box 10360
Bowling Green, KY 42102
Quik-Link #11078

EARLS INDY
302 Gasoline Alley
Indianapolis, IN 46222-3967
Quik-Link #11079

FRAGOLA PERFORMANCE SYSTEMS
(reinforced hose, hose ends, fittings, adapters)
888 W. Queen St.
Southington, CT 06489
Quik-Link #11080

GEAR HEAD TOOLS
(aluminum AN wrenches)
P.O. Box 21887
Carson City, NV 89721
Quik-Link #11081

GOODRIDGE USA INC.
(reinforced hose, hose ends, fittings, adapters)
529 Van Ness
Torrance, CA 90501
Quik-Link #11082

JIFFY-TITE CO.
(fittings, quick-connect fittings)
4437 Walden Ave.
Lancaster, NY 14086
Quik-Link #11083

KOUL TOOLS
(braided hose assembly tool)
405 Jones Dr.
Lake Havasu City, AZ 86406
Quik-Link #11084

RUSSELL
(reinforced hose, hose ends, fittings, adapters)
P.O. Box 2936
Torrance, CA 90509
Quik-Link #11085

XRP
(reinforced hose, hose ends, fittings, adapters)
5630 Imperial Hwy
South Gate, CA 90280
Quik-Link #11086

SEALS/CRUSH WASHERS FOR STRAIGHT THREAD
With NPT threads, simply apply Teflon sealing tape or compound. However, when using an AN adapter that features straight thread at one end, you need a sealing washer. Depending on the applications, you’ll need either an O-ring or a crush washer. O-rings are available in both Buna N synthetic rubber and in Viton. Buna is compatible with most fuels, hydraulic fluids and lubricants up to about 275 degrees F. Viton is preferred for synthetic lubricants, oxygen-bearing fuels and additives and non-ether-based brake fluids. Viton also offers better scuff resistance, longer service life and offers a higher operating temperature range of about 400 degrees F.
Crush washers do exactly that….they crush under compression, providing the needed seal between two flat surfaces, where there is no groove relief to accept an O-ring. Crush washers are commonly available in aluminum and copper. Banjo fittings, for example (as used on brake line connections to calipers) require two crush washers…one between the banjo fitting and the caliper, and one between the banjo fitting and banjo bolt head.
Crush washers MUST match the inside diameter of the adapter. Whether you’re dealing with aluminum or copper, it is highly recommended to never re-use old crush washers. Always replace with new, since once they’re crushed, they don’t “spring back” to their original thickness, and the “fingerprint” will have mirrored the parent surface of the original installation, and might not seal against a different surface.
Crush washers are generally available in hole diameters including 3/8″, 1/2″, 10mm, 12mm, 7/16″ and 9/16″.
Another…and better approach to sealing banjo assemblies are aluminum washers with built-in rubber O-rings. This approach offers the best of both worlds…the strength and crush of aluminum, plus an O-ring that expands to provide a superior seal. This type of sealing washer is available in two basic formats (one is of American design and the other was born in England). The American design, called the Stat-O-Seal, features a synthetic rubber O-ring captured (mechanically locked) inside the I.D. of an aluminum washer. This is a great choice to seal anything that normally would use an aluminum or copper crush washer.
The English-origin version is called the Dowty seal, which is similar to the Stat-O-Seal, but the O.D. is smaller and the washer is thicker. Either works well, but the Stat-O-Seal is more readily available.
As an example of the superior sealing offered by a Stat-O-Seal, I recently reconfigured the front brakes of a 1973 Duster (fitted with a non-original 426 Hemi) to disc brakes. The owner wanted an “OE” look, so I chose single-piston cast iron calipers from a well-known caliper remanufacturer. I initially installed copper crush washers at the banjo fittings, but could not achieve a seal (constant wetness). I tried different-thickness copper crush washers, and even tried aluminum crush washers, but to no avail. Further inspection showed that the sealing seats on the calipers (where the crush washer was position between the caliper seat and the banjo fitting) were never re-faced after the caliper bodies were blasted during cleanup. The sealing seat surface was irregular (not milled). I exchanged the calipers for replacements, but got the same pitiful results. Finally, I replaced the crush washers with Stat-O-Seals. Guess what? Instant perfect seal. No leaks, no more cussing and no more re-bleeding.

O-rings are available in either BUNA N or VITON.

Aluminum crush washers.

Stat-O-Seals. These feature synthetic rubber O-rings captured inside aluminum washer shells. These buggers work great.

Dowty seals. These sealing washers are of British origin. They feature a smaller-O.D. and a thicker cross-section than Stat-O-Seals, but essentially work the same way, with an O-ring inside an aluminum housing.

While we’re on the subject of sealing fluid, here’s something many people aren’t aware of: If you have a damaged AN 37-degree sealing surface (hose end of adapter) that may have been caused by galling when assembled dirty, etc., you can make a quick and easy field-fix without the need to replace the hose end or adapter. Aluminum conical seals are available in all AN sizes. This is simply a small, shallow conical “cup” that matches male and female seat angles. Simply push the conical seal over the male cone and reassemble the hose end to the adapter in the normal manner.

Conical seals offer a quick field-fix for damaged 37-degree AN hose end-to-adapter connections.

HOW TO ASSEMBLE -AN HOSES
NOTE: -3 and -4 sizes are relatively small in diameter. Especially for brake hose applications, these are very difficult to assemble by hand and often require crimped hose ends. For brake lines, or high-pressure hydraulic clutch hoses, don’t try to make your own. Buy brake hoses or clutch hoses already assembled in the lengths you need.
The following instructions apply only to stainless steel braided hose and appropriate hose ends. Crimp-type hose ends require special crimping dies, available from the hose maker. Dedicated hydraulic crimping machines are also available and come in handy, especially if you plan to assemble a bunch. Slip-on hoses and barbed nipples are self-explanatory. Simply “slip” the hose over the barbed nipple. Be aware that this isn’t as easy as it sounds, since the fit will be very tight. Eat your Wheaties before tackling slip-ons.

CUTTING STAINLESS BRAIDED HOSE
When you buy a length of -AN stainless-steel braided hose and plan to cut pieces to desired length and make your own assemblies, you first need to know how to properly cut the hose.
Yes, you can use a hacksaw, but frankly, that method stinks. It’s difficult to obtain a square cut. To do so, you need to use a special hardened blade, and chances are very high that you’ll end up with frayed wire ends that you’ll then need to snip off with wire cutters (by the way, snipping this hard stainless wire braid isn’t as easy as it may seem). If you secure the hose in a vise to make your cut, you’ll have a tendency to smash the hose out of round, which will only aggravate the problem.
The best method is to use an abrasive “chop saw.” First, wrap the area to be cut with electrical tape or a quality bodyshop masking tape (wrap the hose tightly). Mark your intended cut on the tape, carefully cinch the hose in the saw’s vise without distorting it, and let the abrasive wheel slice through. Don’t apply a bunch of pressure on the saw arm. Light to moderate pressure works best.
Once the cut is made, remove the tape and thoroughly rinse the hose out using compressed air to remove all wire and rubber particles. This is important! Make sure the hose is clean inside. Naturally, you must always wear eye protection when cutting hose, when trimming stainless braid or when blowing hose clean.

Mark the hose at the cut location. Body masking tape works well not only as a background for marking, but to help retain the stainless steel braid ends once the hose is cut.

An electric “chop saw” fitted with an abrasive cutting wheel works well for cutting stainless-steel braided hose.

Position the hose on the saw, making sure that the saw clamp is adjusted for a 90-degree cut. Avoid cutting the hose at an angle.

Allow the saw wheel to gain full speed before contacting it to the hose. Maintain steady, moderate pressure. Don’t push so hard as to deform the hose.

This is exactly what you don’t want. This is what happens when someone tries to cut stainless-steel braided hose with a dull hacksaw, with “snips” or by cutting the hose without wrapping the cut area with tape. This cut is useless. Don’t even attempt to install a sloppy hose like this onto a hose end. If you start to snip the frayed ends with metal snips, you’ll just end up making more of a mess. If you have a cut like this, simply start over.

This hose was cut on the abrasive wheel chop saw. Once the cut is made, be sure to blow the hose out with compressed air to remove bits of rubber and braid. We lightly secured this hose in a vise only for the photo.

If you plan to assemble -AN hose ends, buy a pair of these soft aluminum vise jaws. You can secure aluminum hose ends or adapters in these jaws without damaging the material. If you keep the jaws clean, you can also eliminate surface scratches on the anodized pieces. The jaws feature female V-cuts that accept the hex of the hose end or adapter, in either horizontal or vertical planes, as you wish.

The backside of the soft jaws feature a step (this locates the jaw onto the top surface of the vise jaw) and a magnet, which holds the aluminum jaw to the vise.

A pair of soft jaws installed on a vise. These jaws will come in handy for plenty of non-related future fab work as well, such as whenever you need to secure a piece of aluminum round bar stock, etc.

Here we insert a stainless-steel braided hose into a hose end collar. There are many ways to go about this. Often, I simply screw the hose end collar onto the hose by hand. We’re simply showing the collar in a vise for illustration. However you approach this, be careful of the braids at the cut end. If you’re going to draw blood, this is when it’s gonna happen.

Push/twist the hose into the hose end socket roughly 1/8″ to 3/16″ short of the threaded area.

Check to make sure that the hose is fully seated in the hose end socket. Don’t push the hose into the threaded area If the hose (and its stainless-steel braid) enters the threads, they can jam between the male and female threads when the hose end is assembled.

The section of the hose end that features the metal sleeve threads into the hose end’s socket. Apply a bit of lube to the sleeve and to the threads to aid assembly and to prevent galling. A light lubricant such as WD-40 or lithium grease works fine.

A 45-degree hose end shown here before being fully tightened. The hose end’s socket (attached to the hose) can be secured in an aluminum vise jaw, while the hex on the hose end’s threaded collar is tightened. Note that some hose ends are designed to rotate, while others are designed to retain a fixed position once tightened. If the hose end is not designed for rotation after it’s assembled, make sure that the angle aligns with your intended fitting once installed.

Once the hose end collar is installed, I like to place a piece of tape on the hose, flush to the base of the collar. This provides a visual reference so you will still be able to tell if the hose begins to pull out of the collar during the rest of the hose end assembly.

Here, the hose end collar is secured in aluminum soft jaws on the vise. There’s no need to tighten the living daylights out of the jaws. Just snug the jaws to prevent the collar from moving.

Apply a bit of lube to the hose end’s nipple and threads.

Insert the hose end’s tube into the collar, being careful to center the nipple to the hose I.D. If you try to insert the nipple off-center, you can force the nipple edge into the hose rubber, damaging the hose. Take your time. You’ll be able to feel the nipple entering the hose.

Continue to insert the nipple until you can engage the threads. Make sure the threads are not crossed. Tighten as far as you can with your fingers, verifying that thread engagement feels/looks good.

If you care about the finish of your hose end, use a clean aluminum -AN wrench to tighten the hose end assembly. Here we’re using a -10 wrench, which fits our -10 hose end.

Continue to tighten the socket/tube into the collar, using moderate pressure. Do not overtighten! Remember: These are aluminum parts. Also, as you tighten, the nipple seals into the hose I.D., creating a leak-proof connection. Note: it’s a good idea to apply a bit of a push of the hose towards the collar during tightening just to make sure the hose isn’t pushed out of the collar. Again, observe your reference tape.

You’ll know the assembly is fully tightened when it stops or offers too much resistance. This narrow nut is almost touching the collar.

Blow with compressed air again. Once a hose is fully assembled, I like to run hot soapy water through it, followed by compressed air, followed by air-drying. Do everything you can to make sure the hose is clean inside. I know plenty of guys who gripe about clogged carburetor jets or stuck needles and seats when it’s their own fault because they didn’t take the time to inspect and clean new hose assemblies before installing them.

Hose end fully installed onto a braided hose. Note that the reference tape only moved about 0.020″, which is fine. Using the tape helps. If the hose walked out noticeably, the hose end socket/nipple must be removed, the hose repositioned and re-assembled.

SPECIAL-PURPOSE ADAPTERS
(Unique adapters for special applications)

90-degree dash AN male to straight-thread male (note sealing O-ring on straight thread).
This adapter features swivel for rotation of male AN.

90-degree dash AN female to NPT male swivel.

90-degree dash AN male to dash AN female swivel.

90-degree dash AN female to dash AN female swivel.

90-degree dash AN female to dash AN female swivel, low profile.

45-degree dash AN male to dash AN female swivel.

45-degree dash AN female to dash AN female swivel.

45-degree dash AN female to dash AN female swivel.

Dash AN female to tubing adapter. This allows connection between flexible AN hose to a tube. The tube side seals on a compression fitting.

Dash AN female to dash AN male reducer.

Dash AN T female swivel on run. All three connections are dash AN (featuring 37-degree cone seating). This version features two male AN and one female AN, all the same size.

Dash AN T female swivel on branch. This adapter features three same-size AN connections, with two males on the main run and one female at the branch.

Straight AN female swivel coupling. Same size female AN at each end. The two halves swivel.

Straight dash AN female to female reducer swivel coupling. This adapter features two female AN fittings of two different sizes. For example, allowing connection of a -8 AN to a -6 AN.

Straight dash AN female to NPT male swivel adapter.

Extended straight male AN to straight thread. The example shown here features a male -8 AN and a 7/8″ x 20 male thread, with a sealing crush washer. This application would suit certain carburetor feed applications.

Dash AN male to straight thread male. This example features a -6 AN male and a 9/16″ x 24 male thread with a crush washer, suitable for fuel plumbing or other custom application.

Dash AN male to straight thread. The example here features -6 male AN to 7/8″ x 20 straight thread, with a crush washer. Suitable for certain carburetor applications.

Straight male to male dash AN union. Allow connection of two same size hose ends.

Male to male AN reducer. Allows connection of two different-size hose ends. Available in a variety of combinations.

Male AN to male AN 90-degree fitting. Same size AN at each end.

BULKHEAD ADAPTERS
(Designed to allow plumbing through wall surfaces, such as firewall, rear bulkhead, etc.)

Straight bulkhead adapter. Same size AN male at each end. The longer section passes through a hole in a bulkhead wall. The exposed straight threads accept a nut that secures the adapter to the bulkhead. Separate hoses can then be connected to each end of the adapter while the adapter remains in a fixed position.

45-degree bulkhead adapter.

90-degree bulkhead adapter.

AN bulkhead T on run. All three male AN same size. The long section (that will be secured to the bulkhead) is on the main run.

AN bulkhead T. The long section is the T, which mounts to the bulkhead. All three ends feature the same AN size.

Bulkhead nut. This allows you to secure the bulkhead adapter to a wall. Drill an appropriate-size hole in the wall, pass the long end of the bulkhead adapter through the hole, and secure the adapter with this nut.
Always order the bulkhead nut based on the size of the bulkhead adapter
(-3, -4, -6, -8, -10, -12 or -16). Always match nut and adapter material. If the adapter is aluminum, use an aluminum nut. If the adapter is steel, use a steel nut.

CAPS AND PLUGS
(these include caps and plugs for AN 37-degree, AN straight thread and NPT applications)

Dash AN cap. Features a female AN (37 degree sealing cone). Designed to cap-off a male AN fitting. Common uses include capping-off a fitting when hoses are disconnected, to prevent fluid leaks or to protect fluid passages from contaminants (during engine storage, repairs, etc.). All dash AN sizes available.

Male AN plug. This can be used to cap-off disconnected hose ends when not in use. Features a male hex head.

AN straight thread port plug with O-ring seal. For capping-off an AN straight thread port.

NPT internal plug. Features male NPT thread and a female hex drive. For capping any NPT port. Available in all NPT sizes. Remember: always apply Teflon tape or sealing compound during assembly of any NPT thread.

NPT hex head plug. NPT male threads with a male hex head.

STEEL ADAPTERS
In addition to the wide array of aluminum hose ends and adapters, steel components are also available for high pressure hydraulic and other severe duty applications where steel is preferred.

Steel -AN to NPT adapters are available most all of the same sizes and configurations as aluminum adapters.

BARE ALUMINUM ADAPTERS
For those who wish to have their AN adapters custom anodized in other colors, bare, un-anodized aluminum adapters are available from select manufacturers (not all makers offer un-anodized items). If you want un-anodized hose ends, you need to check with the various makers. Depending on existing stock or backorder situations, you might be able to place a custom order, or you might get lucky and be able to snatch what you need from existing stock. There are several anodizing shops in the country that do excellent work. While the “standard” colors that all anodizing shops carry usually include black, blue and red, there are other shops that offer a dozen or more colors, and yet other shops that can attempt to match the color you want.
If you purchased already-anodized hose ends and adapters, but want to change color, this can be done, but you need to be aware of a few things. If the item has already been anodized, and since anodizing is essentially an oxidation process, the surface is now etched. When the original color is stripped off (chemically), the resulting surface will be rather dull. If you like a “flat” look, you’re in business. If you want a gloss surface, you have two choices: each piece must be polished before anodizing, or you can request a clear gloss finish over the color (an option not all anodizing shops offer). From a standpoint of appearance only, be aware that one of the big variables lies with the composition of the aluminum stock. Depending on the hardness and alloy makeup, some aluminum pieces will provide a glossier finish than others. Also, the same color anodizing will appear lighter or darker when applied to different grades of aluminum. If you want all of the custom-anodized pieces to match, be sure that you obtain all of the pieces from the same manufacturer!

Here’s an un-anodized aluminum AN to NPT adapter. If you can obtain these in their “bare” form, the results from custom-color anodizing will be outstanding. Otherwise, if the part must be stripped, it may require polishing before anodizing; or a clear-coat may be applied over the anodized color by the anodizing shop.

HOSE END STYLES

Swivel-Seal straight hose end (Swivel Seal style allows full 360-degree rotation even after plumbing connection).

Swivel-Seal 30-degree hose end.

45-degree low-profile hose end, for added clearance.

45-degree swivel hose end.

90-degree low-profile hose end. This neck style, as opposed to a tube neck, offers a shorter-profile if clearance is a concern.

Swivel-Seal 90-degree hose end.

Swivel-Seal 120-degree hose end.

Swivel-Seal 150-degree hose end.

Swivel-Seal 180-degree hose end.

Straight hose end with male NPT (national tapered pipe thread) on one end, and tube and collar to accept -8 hose.

45-degree low-profile hose end with 3/8″ NPT male threads.

90-degree low-profile hose end with NPT threads.

Straight hose end with male AN thread and 37-degree seat.

45-degree low-profile hose end that features straight-thread with a sealing O-ring.

90-degree low-profile hose end with straight thread and O-ring.

Pictured here is an Earl’s “Auto-Fit” straight hose end. The Auto-Fit design does not allow swiveling after assembly, placing the hose end in a fixed position. The Auto-Fit hose ends are offered in all the same sizes and shapes as the swivel line, but cost a bit less. When you’re performing hose assembly using this style, and if you’re using an angle hose end at each end of the hose, you’ll simply need to pay attention to hose end clock position to align to the fittings.

-AN hose ends are also available for hose slip-on applications. The female thread accepts dash size fittings, but the hose end features a barbed tube. This design offers easy assembly, but is designed to be used only with specific hose intended for this type of application, and will not work with stainless braided hose. This is a popular and economical option for OE replacement hose assemblies. Available in all popular sizes and shapes.
NOTE: Depending on the size of the AN hose end, assemblies with pipe thread connections are available in a full range of NPT sizes, from 1/8″ NPT all the way up to 1/2″ NPT (with 3/4″ NPT also available from some makers).
Generally, hose ends that feature female dash-size connections are designed to accept the same hose dash size at each end (for instance, a hose end may be labeled “-6 female to -6 hose,” which means that a -6 hose will connect to the tube/sleeve end, and the female threaded connection will accept a male-thread -6 fitting). However, some makers offer sizing differentials. For example, a -6 female to a -8 hose hose-end might be available to suit a specialty need. However, the most common approach for hose ends is a design that accommodates the same dash size at each end.

HOSES
We’re all accustomed to seeing braided stainless-steel hose with blue and red hose ends on custom cars and race cars. However, great strides have been made by the various hose makers, resulting in a wide array of choices with various benefits. There’s certainly nothing wrong with stainless braided hose. It works great and looks great. The only downside of stainless braided hose is its weight and its abrasive outer surface. Although the durable stainless braid does a wonderful job in protecting the hose itself, this surface can scratch, or even file-through an adjacent surface if the hose rubs against anything. Where weight savings are needed, and/or abrasion damage needs to be avoided, the industry now offers a selection of optional hose designs that are lighter and that won’t abrade nearby surfaces, but still provide the strong reinforcement and protection for the hose itself.
One type isn’t better than another…it’s simply a matter of selecting the type that best suits a particular application or preference.

A dry sump pan-to-pump scavenge plumbing. Beauty plus brawn. Form and function, etc. You get the drift. It works at a pro level and looks cool to boot.
As an alternative to stainless braided hose, lighter-weight high-performance hose is offered with Kevlar outer woven braid or nylon braided sheathing, and special elastomeric hose that features no outer braided cover. Synthetic rubber hose featuring interior braided fabric sheath (for strength) is available with maximum pressure ratings in the 250 psi range and can be assembled using hose nipples and beaded tubing. Hoses with a tough, abrasion-resistant outer nylon sheathing bonded to a textile inner braid and synthetic rubber liner can be assembled using traditional AN hose ends or crimp hose ends, with maximum pressure ratings in the 1,400 psi range. Ultra-light Kevlar-outer-sheathed hoses are available that weigh about 50-60% lighter than stainless-steel braided hoses, with maximum pressure ratings in the 1,100-1,200 psi range, but may require only the use of dedicated crimp hose ends. A wide range of choices are available today, not only in terms of weight, flexibility and materials, but in colors as well.

-AN THREAD SIZE
The thread size of the AN hose end and its mating fitting are as follows:

Note: UNJ threads simply refer to the thread root shape. UNJ threads offer stronger threads that are less prone to stress fatigue. Without going into a bunch of engineering lingo, UNJ thread features a shallower thread root, with a more gentle curve of the thread root. This reduces stress concentration. UNJ really stands for Unified Controlled Root Radius thread (so why isn’t it called UCRR? Who knows?). The “J” probably refers to the shape of the root curve.

Metric Thread Sizes
AN -4 to 8mm x 1.5
AN -4 to 10mm x 1.25
AN -4 to 10mm x 1.5
AN -4 to 12mm x 1.5
AN -4 to 14mm x 1.5
AN -6 to 10mm x 1.25
AN -6 to 10mm x 1.5
AN -6 to 12mm x 1.5
AN -6 to 14mm x 1.5
AN -6 to 16mm x 1.5
AN -8 to 12mm x 1.5
AN -8 to 14mm x 1.5
AN -8 to 16mm x 1.5
AN -8 to 18mm x 1.5
AN -10 to 14mm x 1.5
AN -10 to 16mm x 1.5
AN -10 to 18mm x 1.5
AN -10 to 20mm x 1.5
AN -12 to 14mm x 1.5
AN -12 to 16mm x 1.5
AN -12 to 18mm x 1.5
AN -12 to 20mm x 1.5
AN -12 to 30mm x 1.5
AN -16 to 16mm x 1.5
AN -16 to 18mm x 1.5
AN -16 to 20mm x 1.5
AN -16 to 30mm x 1.5

Aeroquip’s Pro Crimp 1380 crimping machine allows easy and fast assembly of AN crimp-type hose ends. Photo courtesy Aeroquip
FITTINGS/ADAPTERS
The fitting (also called adapter) allows the connection of the hose end to the component. In some cases, the fitting will be provided as part of the component (for example, an engine oil cooler might already feature welded-on -10 fittings, so a -10 hose end will thread directly onto the cooler). In other cases, you’ll need a separate fitting to finish the connection. Fittings are available with AN threads (and 37-degree flare seat) on one end, and an appropriate thread on the opposite end to fit the component. For example, let’s say that you need to plumb a -10 hose assembly to your water pump-to-heater routing. The water pump may feature a 1/2″ NPT female threaded hole. In order to complete the connection, you’ll need an AN fitting that features a 1/2″ male NPT at one end and a -10 male at the opposite end to attach to your hose end. Fittings are available in a wide variety of both thread size combinations to accommodate any reasonably practical connection between various AN hose ends and NPT threads. Fittings are also available in straight thread (as opposed to tapered pipe thread), for locations that feature straight-thread holes. If the AN fitting features straight thread for the component connection, a sealing O-ring will likely be required.

Fittings, like hose ends, are also available in various shapes, including straight, 45-degree and 90-degree, to further accommodate plumbing routing and clearance issues. With the combination of hose flex and hose end and fitting shapes, it is possible to achieve extremely neat and tidy plumbing routing that would please even the most demanding appearance-conscious builder.
Metric adapters are also available, to accommodate all domestic and import OE vehicle applications for the use of AN 37-degree plumbing connections. The AN threads are the same as always, but the opposite end, instead of featuring NPT or AN straight thread, features metric thread size instead.
AN adapters for metric applications are available in all common AN to metric sizes, including:

This example shows an AN adapter with a male AN (37 degree seat) at the right side as shown here, where the hose end will attach; and a straight thread male at the opposite end. Notice the sealing O-ring at the straight thread side. No thread sealant is required for straight threads. If a cone seat is featured, the mating of the 37-degree seats will achieve the seal. If the AN straight threads feature no seating cone, an O-ring is required for sealing.

This fitting features straight threads and a sealing O-ring, which will mate to an aluminum fuel log for a fuel-injected engine. Notice that the fuel log threaded opening features a recess to accommodate the O-ring.
Note: as far as hose end and fitting materials are concerned, both steel and aluminum are available. For purposes of weight saving and appearance, most people favor aluminum (as you already know, hose hardware makers commonly offer aluminum AN hose ends and fittings in blue and red anodized colors). However, for brake system connections, steel hose ends and fittings are often preferred to avoid the however-unlikely potential for fatigue cracks.
ALUMINUM NPT TO AN ADAPTERS
Fitting adapters that allow connection between pipe thread locations and AN hose ends.
Photos courtesy Earl’s

Straight male AN to NPT adapter. A wide variety of pipe thread and AN sizes are available to suit any requirement.

Male AN “T” to NPT on branch. On branch means that the NPT connection is located between the AN to AN run. Again, a variety of size combinations are offered.

Male AN “T” to NPT on run adapter. On run means that the NPT threaded connection is on the T’s main run.

45-degree elbow male AN to male NPT.

NPT female T. All three ends feature female NPT threads. The flats at the center allow the use of an open-end wrench to hold the adapter steady while installing the three connections.

Female NPT to male NPT reducer. This allows the use of a smaller NPT male fitting at a larger female NPT hole. For example, if the female NPT hole in an intake manifold featured 1/2″ NPT threads at a water jacket port, but you want to connect a 3/8″ NPT fitting, this pipe bushing reducer would allow that change.

90-degree elbow male AN to male NPT. The flat surfaces at the bend accommodate an open-end wrench.

NPT female to NPT female straight coupler. Each end features the same size NPT thread.

Straight NPT male to NPT male coupler, with the same NPT size at each end.

45-degree female NPT to male NPT elbow. Shown here is an adapter featuring the same size NPT at each end (one male and one female).

90-degree female NPT to male NPT elbow. Same NPT size at each end shown here.

90-degree female NPT to female NPT elbow. Same size NPT at each end shown here.

We answer all (or most) of your -AN questions.

by Mike Mavrigian

photos by author

Dash sizes, or AN sizes, were first used in military applications, on aircraft, ships, etc., for hydraulic, fuel and coolant plumbing. The tough, braided/reinforced hose, coupled with threaded connections that were reliable in combat conditions, led early racers to buy military surplus hose, hose ends and fittings in the years following WWII and the Korean War. The racing community quickly made this type of plumbing popular, resulting in common use in today’s performance and racing markets. The term AN (a common abbreviation for Army/Navy specification) sticks with us to this day. That’s why the reinforced hose/hose end assemblies we see today are referred to as AN assemblies.
So, we refer to these hoses, hose ends and fittings sizes with the word (or symbol) dash, or by the term AN, or by the term -AN. It all means the same thing. For example, “I’m plumbing my fuel system with dash 6 hose” or “I used dash 8 AN hose for my carburetor feed.” When in written form, the dash symbol (-) or the word dash might be used.
-AN (ARMY/NAVY) hose sizing is based on single and double-digit identification numbers. Common sizes for performance automotive applications include -3, -4, -6, -8, -10, -12, -16 and -20 (the larger the number, the larger the hose diameter).
-3 and -4 sizes are typically used for brake line applications, small oil lines, some small fuel line applications, pressure gauges and vacuum lines.
-6 size is typically applicable for fuel and oil plumbing
-8 size is typically used for fuel, coolant and oil plumbing
-10 size is typically used for oil, fuel or heater hose plumbing
-12 size is typically used for coolant, large fuel delivery or dry-sump oil
-16 size is typically used for coolant, dry-sump oil or large fuel delivery
-20 size is typically used for coolant (radiator hose)
What do these AN dash numbers really represent? Actually, there is a logical reason for these numbers, which otherwise might seem like made-up codes. The dash number refers to the hose inside diameter, in denominations of 1/16″ of an inch. For example, a -10 size translates to 10/16″, or 5/8″ inside diameter. This is an easy way to understand dash sizes. Just think in terms of 1/16″ increments. A -6 means that the inside diameter is 6/16″ (or 3/8″). A -8 size is 8/16″ (or 1/2″) inside diameter. Just remember that the format is based on 1/16″.
Not to make things confusing, but those 1/16″ increments are “nominal” numbers that indicate the O.D. of the hose end’s internal metal tube (this tube slips into the hose). In reality, most AN hose makers actually make their hoses a bit on the tight-tolerance side, to the tune of about 1/32″ smaller than the theoretical nominal diameter size, which aids in hose sealing onto the hose end’s tube. So, a -6 hose, which theoretically should have an inside diameter of 6/16″ (3/8″ or 12/32″), actually has an inside diameter of 11/32″. Nevertheless, using the 1/16″ theory as your guide will help you to easily visualize what the inside diameter will be. For example, a -6 hose will provide about a 3/8″ I.D. and a -8 hose will provide about a 1/2″ I.D. If you’ve decided that your fuel line should feature a 1/2″ inside diameter, you know that a -8 AN size will be the correct choice.

(NOTE: The above sizes are based on Russell hose. Outside diameters may vary among hose manufacturers and among hose materials. Operating pressure ratings will vary depending on the specific type of hose construction).

The “standard” of the AN hose world, at least for automotive performance applications, is a red and blue anodized finish. Although aluminum fittings and adapters are usually solid blue (sometimes red), two-piece hose ends are generally blue and red. Color shades, as well as finish gloss, will vary among makers, with items also offered in black or clear anodized finishes as well. So, if it’s important to you that everything looks matched, it’s best to stick with one particular manufacturer’s hose ends and fittings. Remember: Anodizing is not a “coating.” It’s actually a controlled oxidation process that is used to protect the finish of an alloy, to allow the use of a color dye and/or to harden the alloy surface. A dull, non-gloss appearance is actually quite normal. If a higher gloss is desired, manufacturers can polish the aluminum beforehand, and they even have the option of using a gloss clear anodizing. The point is to look at the various makers’ offerings, and if appearance is critical, decide what color and finish you prefer. Then stick with that one manufacturer’s hardware. Otherwise, if you mix it up, you’ll have different shades of blues and reds and gloss and flat finishes under the hood. If it’s a race car, function is most important. But if it’s a show car or street rod, it’ll look best if all pieces match. These samples from XRP feature a stunningly beautiful appearance, with rich color and satin gloss finish.

HOSE ENDS
Hose ends attach directly to the hose and provide a high pressure seal. The hose end features a two-piece arrangement consisting of a socket (this slips over the end of the hose and features a female threaded opening) and a male/female tube assembly. The male/female piece features a male threaded nipple that threads into the hose end socket. The female (exposed) end is then ready to thread onto a male fitting at the desired installation location. These components are called “hose ends” because they comprise the end of the hose.

Note: Although this is the most common configuration, not all assembled hose ends feature female threads. Some makers offer special male threaded ends that fit into female fittings.

Here’s a lineup of common -AN hose ends, shown here simply for size comparison. From left, shown here is a -6, -8, -10, -12, -16 and a 45-degree -20.

Here’s the same lineup pf -6, -8, -10, -12, -16 and -20 hose ends, with a U.S. quarter in the foreground, just to give you a size reference.
Hose ends not only allow hose connection and sealing, but because hose ends are available in various shapes, the selection of the hose end shape will allow you to obtain installed angles necessary for clearance and preferred routing. Hose ends are available in straight, 30-degree, 45-degree, 90-degree, 120-degree, 150-degree and even 180-degree shapes. With regard to angled hose ends, these are also offered in two basic “profiles,” including standard profile and low profile. Standard profile hose ends feature a tube neck, while low profile hose ends feature a forged or machined neck that shortens the hose end’s distance from the fitting connection to the bend. Low-profile versions are good choices where installation space is at a premium.

Here’s a 90-degree hose end in a standard profile (note the tubular neck). In this example, the red end (upper left in this picture) attaches and seals to the hose, in practical terms becoming an integral part of the hose. The blue end (lower right in this picture) features a female AN thread and 37-degree internal seat, which will attach onto a male AN fitting.

(Photo courtesy Aeroquip)

Here’s a -16 straight hose end with the collar removed. Hose ends feature a nipple that inserts into the I.D. of the hose.

Note the smooth bore in this hose end for unrestricted fluid flow. This is typical of all makers hose ends.

The male threads on hose ends (to retain the hose end collar) are very fine. Even with a new hose end straight out of the box, make sure that the threads are clean and free of any contaminants. The anodizing helps to harden the aluminum surface, but you can still gall the threads if you don’t pay attention.

The inside of this hose end’s collar shows the wide-spaced “coarse” threads on the hose side of the collar. These threads, or ridges, help to retain the hose.

Shown here are three straight -AN hose ends and straight -AN to NPT adapters. From left: -6 straight hose end and -6 male to 3/8″ NPT male straight adapter; -8 straight hose end with -8 male to 3/8″ NPT male straight adapter; and -10 straight hose end with -8 male to 1/2″ NPT male straight adapter.

This simply illustrates how a -AN hose end attaches to a -AN adapter. The hose end pictured here features a female threaded port with a 37-degree female (concave) sealing seat. The adapter shown here features a male threaded -AN tip with a 37-degree male (convex) sealing seat. The two angled seats mate, creating the seal. All -AN connections obtain their seal by the mating of these angled seats (these angled seats are sometimes called cones). No additional sealing material is required, so there’s no need to add thread tape or compound to the -AN threads. -AN seals at the cone seating. NPT (tapered pipe thread) always requires thread tape or compound. Straight -AN thread that does not feature an angled seat requires an O-ring for sealing.