Build, text and photos by Mike Mavrigian
This final article installment covers the completion of the 408 LS build, along with the engine dyno results. Our radical-looking baby pulled a respectable 670.5 HP at 6500 rpm and 581/7 lb-ft of torque at 4900 rpm.
The LQ9’s original valley cover is a cast aluminum piece that’s downright ugly. It features two big bores that accommodate the valley-mounted knock sensors. Since I don’t plan to use knock sensors, and since I definitely didn’t want those two ugly holes visible on the cover, I opted to fabricate my own valley cover using ¼”-thick T6061 aluminum (starting with a piece of flat stock 6” wide x 20” long). The OE cover measures exactly 6” wide, so I only needed to cut my raw piece of flat stock to length, contour cutting at the rear to clear the OE oil pressure sensor location (and drilling bolt holes). Since the LQ9 features its cam sensor at the top rear of the block, and since I’m using an LS2 front cover that features a front-mounted cam sensor, I also needed to plug the original cam sensor bore in the block. Instead of making a separate plug/cover for the cam sensor hole, and since the top surface of the LQ9 cam sensor location is flush with the mounting surface of the valley cover, I simply made the new valley cover a bit longer (total finished length of 19 7/16”) to also cover the cam sensor bore. Mounting the new valley plate now requires 11 bolts instead of the original 10 (10 bolts for the standard locations plus one bolt at the cam sensor bracket hole). All bolts for the valley cover are ARP 12-point polished stainless steel, 8mm x 1.25 x 20mm (snugged to 18 ft-lbs). Because my fabricated valley cover doesn’t feature a milled gasket ring recess (like the original), I sealed the cover with a thin bead of RTV. My favorite choice for this type of application is Permatex’s “The Right Stuff.” This is a high-density black RTV that does a killer job of sealing. In order to keep things neat and tidy, I first masked the valley plate edges and surrounding adjacent block surfaces. After the cover bolts were tightened 10 18 ft-lbs, I then carefully wiped off any excess RTV that squished out. With the masking tape then removed, the result is a clean installation with no RTV exposed.
Instead of using the ugly OE top cover that features the two huge holes for the original knock sensors, I simply fabricated my own top cover using a slab of aluminum sheet stock. I extended the rear of the cover to hide the original entry hole for the LQ9′s rear-mounted cam position sensor. The cover was prepped, etch-primed and painted to match the block. The cover is sealed with an OE-replacement aluminum-core gasket from Victor, and secured with a series of ARP 12-point polished stainless bolts.
Aftermarket valley covers are available for a few LS variants, but I couldn’t find one for the LQ9 (that would also cover the rear cam sensor hole). Besides, the aftermarket covers are pricey ($120 and up). My investment for the fabricated cover: $15 for the flat stock and about 2 hours of my time.
As far as appearance is concerned, the options that I considered included painting it orange-red to match the block or having it wet-dipped to look like black carbon fiber. Unfortunately, the water transfer (hydrographics) source that I’ve used in the past recently went out of business. Considering the deadline I faced with this particular build, I didn’t have the time to locate another source (time to sample their work and time to have my stuff done), so I simply painted the plate. All of the other water transfer printing shops that I contacted were out of state and their current turn-around times were 3-4 weeks. I think it would have looked really cool in carbon fiber, but time simply wasn’t on my side.
My choice of using Holley’s Hi-Ram LS modular intake manifold with dual carbs falls under the heading of “why not?” While it seems that the majority of LS users tend to go with fuel injection or maybe a single carb, I just couldn’t resist slapping an in-your-face tunnel ram setup onto our latest build.
The intake manifold, Holley’s LS Modular Hi-Ram carbureted unit, P/N 300-226, is designed for use with LS1/LS2/LS6 cathedral port heads. The intake manifold assembly I chose consists of two parts: the lower base P/N 300-226, along with the upper carb base P/N 300-216. This top allows the mounting of two 4150 series side-mount carbs. Holley offers the Hi-Ram in several configurations, with lower bases available for cathedraul port heads or for LS3/L92 rectangular port heads, and tops that accept 4150 series carbs, 4500 series carbs or EFI throttle bodies.
Holley’s LS Modular Hi-Ram intake lower base. Holley offers this for both cathedral and rectangular port LS head designs.
Our manifold top accommodates twin side-mounted 4150 series carbs. Other tops are available for 4500 series and for EFI throttle bodies.
The top plenum secures to the lower base with a series of 1/4″x20 socket head cap screws. Note the blank bosses on the front and rear runners to allow throttle bracket assemblies, and the blank bosses along the decks to allow fitting nitrous injection.
During test fitting, I port-matched the intake to the heads, which required very minimal mods. The alignment and dimensions were already very close straight out of the box. The lower manifold decks were also machined ultra-straight, with nicely executed mating from front to rear on both heads. The lower manifold base is sealed via supplied O-rings that insert into machined grooves in the manifold decks. According to Holley, the Hi-Ram manifold is designed for use on naturally aspirated and forced induction engines in the 6.0L to 7.0L range, accommodating power up to the 7000-8000 rpm range.
Port size is 2.49” high x 1.21” wide. Runner length is 6.58”. The as-cast runner cross sectional area is tapered from 4.25” squared to 2.53” squared.
INTAKE MANIFOLD FIT
Depending on the cylinder heads, the intake manifold base may initially interfere with the cylinder head intake decks at the top of the intake manifold flanges (outer edges hit the un-milled section of the heads, immediately above the milled surface of the heads’ intake decks). I encountered this with a set of BMP Warhawk heads, but not with the Trick Flow heads. If you run into this, you could mill the cylinder head intake decks further upwards (increasing the height of the milled surfaces to the tune of about 0.060”). Or you can chamfer the outer edges of the intake manifold flanges instead (removing a bit from the manifold is easier).
Once the intake manifold is properly mated to the head intake decks, be sure to inspect port alignment and correct if needed in order to gently blend the intake manifold ports to their respective ports on the heads. With either the BMP or Trick Flow heads, all manifold-to-head bolt holes aligned perfectly, so no fiddling was required at those locations.
The intake manifold is secured to the heads with ten 6mm x 1.0 fasteners and is sealed with silicone bead seals. Apply a light coat of oil or lithium grease to the O-ring seals and insert them into the seal groove that surrounds each cathedral intake port. The lube will help to hold the seals in place during handling.
The entry ports on the manifold base are neatly radiused for improved air flow.
Each intake port features a machined groove that accepts an OE type O-ring seal.
In the midst of port matching, I also test fit all intake port O-rings for fit. The CNC machined O-ring grooves were consistent, with correct shape, width and depth.
Prior to final installation, I test fit to check for clearance issues. The Holley lower manifold required no clearance grinding at all in terms of clearance at the upper cylinder head areas and at the top engine cover.
The upper plenum seals to the intake manifold’s lower base with an O-ring that nestles into a machined groove on the top deck of the lower base. This O-ring wire is supplied as a straight length. Once inserted, carefully cut the excess to create a butted mating between the two ends, and then seal the ends together with a drop of Super Glue.
The manifold kit includes 6mm studs, washers and nuts. I decided (primarily for the sake of appearance) to use a set of 6mm x 1.0 x 60 stainless SHCS and stainless flat washers from Totally Stainless. I still made use of the Holley-supplied studs for manifold placement…since the fasteners are vertical, placing one at each outer corner provides a neat way to lower the intake manifold down to the heads, with the studs serving as guides. Once the manifold was oriented in place, I finger-installed SHCSs in the remaining locations, then removed the four studs and finished placing the SHCSs. I applied a small dab of ARP moly to the screw threads before installing.
All ten fastener locations are initially torqued to 50 in-lbs, followed by a final 106 in-lbs. It’s important to follow Holley’s recommended tightening pattern (starting at the center and working your way outward).
The upper plenum secures to the intake manifold with twelve ¼” x 20 x 7/8” SHCS (socket head cap screws). Before mounting the upper plenum, you’ll need to install the round-profile bead seal (“O-ring”) to the groove that’s machined into the intake manifold’s plenum flange. This seal is supplied extra-long (a single straight length). Insert the seal into the groove, and carefully cut to length to create a tight mating end-to-end. Lift the two ends out of the groove, place a drop of SuperGlue to the ends and secure the ends together. Once the glue sets, reinstall the seal.
The intake manifold flange features open holes, while the upper plenum holes are threaded. As a result, the screws are inserted from the bottom of the intake’s plenum flange. Lightly lubricate the threads and install, tightening to Holley’s spec of 130 in-lbs. I used a set of stainless SHCSs and washers from Totally Stainless.
As long as we were already carried away with the tall, stick-out-of-the-hood intake setup, I opted for Holley’s top-of-the-line Aluminum Ultra HP carbs, P/N 0-80801RD, sized at 600 cfm. This isn’t your traditional 4150 series carb. The Ultra HP is 38% lighter (taking advantage of aluminum for the base, metering blocks, body and bowls, for 97% aluminum construction. While a new Hard Core Gray anodized finish is available, I opted for the natural tumble-polished finish, accented by red anodized billet base and metering blocks.
The aluminum Ultra HP carb is a no-nonsense performance design that’s lighter and more adjustable. For this build, I opted for the tumble-polished body and bowls accompanied by red anodized billet metering blocks and base. Fuel level sight windows are featured on each side of both front and rear bowls.
The Ultra carb weighs in at a mere 4.5 lbs. Air bleeds were moved outward to allow a smoother transition of airflow from the top into the venturis, Hex head squirter screws were contoured for streamlined airflow.
Inlets are featured on each side of each bowl, providing a choice to suit your plumbing needs.
Integrated idle bypass valve eliminates the need for holes in the throttle plates and allows for proper adjustment of idle while maintaining correct throttle plate to transfer slot relationship, which aids in maintaining decent idle when using a radical camshaft profile.
Other cool features of these carbs includes 20% more fuel bowl capacity, fully adjustable (emulsion bleeds, power valve channel restrictors and idle feed restrictors), with power valve channel restrictors machined lower in the metering block for improved fuel delivery to the power valve circuit. Each bowl features easy to view glass sight windows. The accelerator pump channel on the Ultra HP is internally drilled, eliminating the need for an external plug. Another very cool feature are integrated pry-assist points to ease fuel bowl removal without damaging bowl gaskets or gasket surfaces. The bowl vent whistle is a snap-in design for quick and easy replacement. The billet base features elongated (dual pattern) mounting holes for mounting to 4150 square flange or Dominator large flange intake manifolds. Since the Ultra HP is really designed for no-frills race applications, the base plate features a race-only throttle lever, with all unnecessary street attachment points and tangs removed. The new Ultra HP carbs include a long list of additional new features. Basically, this series is designed for ultimate performance coupled with ease of adjustment/service features resulting from years of development.
While I chose a pair of 600 cfm carbs for this LS build, the Ultra HP is also offered in 650, 750, 850 and a true 950 cfm version.
Plumbing a dual-carb, sideways-mount setup is always a challenge. While several approaches were possible, I initially planned to run –6 AN 45-degree hose ends from the carb bowls down to a 4-port fuel distribution block that would be mounted to the engine’s valley cover (holes could be drilled and tapped into the 0.250”-thick cover) in order to secure a fuel block, along with stand-off spacers to reduce ambient engine heat to the fuel block. The black braided –6 hose would then connect to the fuel block with 45-degree –6 hose ends. The rear (inlet port) of the fuel block could be fitted with a –6 male fitting to accommodate fuel feed and a regulator.
However, after anguishing over the fuel plumbing plan for longer than I care to say, I finally decided to plumb the carbs with 3/8” OD aluminum fuel line, using –6 tube nuts and ferrules. Both carb’s lines are fed through a 5-way billet aluminum fuel manifold from Peterson Fluid Systems (their P/N 10-0071). This features a single –10 male inlet and a staggered group of four –6 male outlets. The Peterson manifold also features two handy mounting tabs, which allowed me to mount the unit to the rear of the tunnel ram intake via a fabricated bracket (the tabs accommodate #10 screw size). I fabricated the mounting bracket (allowing attachment of the Peterson fuel manifold) using aluminum 2×1 L-channel stock. This is secured to the two rearmost 1/4×20 cap screw locations where the upper plenum mounts to the intake manifold. This location keeps the fuel lines away from higher heat areas (as opposed to my original thought of mounting a fuel block to the valley cover).
Once our fuel line design was established, Birchwood’s Eric Ritz begins fitting the 3/8″ aluminum tubing.
Each section of tubing running from the carbs terminates to this 5-way billet aluminum fuel manifold, which features a set of four -6 AN fittings for carb line connection and a -10 AN lower fitting for fuel entry from the fuel pump. Pictured here is the fuel manifold temporarily mounted to an unfinished aluminum mounting bracket during tube layout design.
Pictured here is the completed mounting, with the bracket shaped to fit and all four tubes secured to the fuel manifold via -6 AN tube nuts and ferrules.
A view from the right side. The mounting bracket was made to clear the PCV’s T-fitting and hose. All fuel tubes were hand formed with extreme attention to detail. All horizontal runs are parallel and at the same height.
The left side fuel line running from the front carb’s bowl was bent to provide working clearance for the throttle linkage.
Of course, cutting, bending and flaring the tubing required a bit of tedious hand bending in order to obtain a pleasing appearance. This task was artfully handled by Birchwood Automotive’s Larry and Eric Ritz in about 3 hours, using a hand tubing bender, a 37-degree flaring tool and tons of patience.
Once the lines had been fabricated, they were removed and polished to a satin luster using a buffing wheel and polishing rouge, followed by hand-polishing with Wenol polishing paste. Lines were then washed and rinsed and re-installed.
Note: If you plan to plumb using tubing that you intend to connect with –AN fittings, be aware that –AN typically features a 37-degree sealing surface. When using –AN tube ferrules and nuts, a single flare will suffice. However, a common flaring tool will only offer a 45-degree flare, which won’t provide the needed seal. An example of a 37-degree flaring tool kit is the one from Fragola, P/N 900500 (actually made by Imperial), which accommodates a range of tube diameters including 3/16”, ¼”, 5/16”, 3/8”, ½” and 5/8” OD. The tool is a bit pricey at around $169, but it will create the needed 37-degree flare.
With the engine installed in a vehicle, it would be easy to then connect an adjustable pressure regulator, pressure gauge and filter at a convenient underhood location.
A dual-carb throttle linkage kit originally part numbered for biog block Chevy was modified to work with the LS setup. I cut the bearing pivot stand-up from its original base and tig-welded it to a piece of aluminum bar stock, drilled to mount to the intake manifold. The blank bosses at the front and rear of the intake manifold were drilled and tapped for 1/4″ x20 thread.
A left side view of the completed fuel line setup and throttle linkage.
As if the induction system wasn’t tall enough, I decided to slap on a pair of 8”-tall spun aluminum velocity stacks. Hey, if it’s worth doing, it’s worth doing to excess. Each stack features a stamped aluminum screen disc that rests on an inside diameter lip. A ¼” x 20 stud and nut secures the screen to the carb, which holds the stack securely in place. I cut a pair of studs at a length of 2.50”, and installed the studs to the carbs with 1/4×20 female to 5/16×18 male adapters (since the carbs feature 5/16” x 18 female threads). I secured the screens and stacks to the carbs using “Top Seal” 1.5”-diameter knurled aluminum air cleaner lid nuts from Cam Motion. I purchased the stacks (with screens) from CP Performance, a race-boat supplier in California.
TAYLOR/VERTEX VALVE COVER ADAPTERS
Taylor’s “Spacer-Max” P/N 555701 (1999 –2009 LSx) adapters allow you to easily mount Gen 1 smallblock Chevy valve covers, if you wish to eliminate OE-type valve covers and the sight of coil packs mounted atop the covers.
The kit includes Fel-Pro silicone bead gaskets P/N VS50504R (or you can use GM P/N 12560696 gaskets). These bead gaskets will create the seal between the cylinder head’s valve cover rails and the adapters. For sealing the SBC valve covers to the Taylor adapters, Taylor recommends Fel-Pro cork-laminate gaskets, P/N 1604 (5/16” thick). The Taylor kit also includes eight 6mmX1.0 X 45mm SHCS (socket head cap screws) with loc washers and flat washers.
Installing the adapters is easy. With valve covers removed, secure the adapters (with O-ring seal installed) to the heads using the same female threaded holes in the heads used by the OE valve covers. Apply threadlocker and tighten the 6mm SHCS (socket head cap screws) to 106 in-lbs.
Taylor’s valve cover adapters bolt to the cylinder heads with four 6mm SHCS. The underside of each adapter features a milled groove that accepts a silicone bead seal (the same OE type seal normally used for OE valve covers).
Here we’re test fitting a Taylor valve cover adapter to a Trick Flow head, to check for fit and valve spring clearance.
Since our Harland Sharp rocker arms are bridged together on common shafts, the rockers must be installed prior to installing the valve cover adapters. During test fitting, we found no clearance issues at all regarding the Taylor adapters (springs, rockers, etc.). With the adapters secured, I installed ARP radius-nose 1/4″x20 studs and cork-rubber smallblock Checy valve cover gaskets. Using studs always eases gasket and valve cover alignment.
Note: the supplied 45mm-long 6mmx1.0 bolts will work, but (even with the flat washers and loc washers) may come very close to bottoming out in the cylinder head valve cover threaded holes, depending on the specific cylinder heads. After measuring the depth of the four valve cover threaded holes on a pair of BMP Warhawk heads, the 45mm-long screws tended to bottom-out, so 40mm lengths were needed.
For attachment of the SBC valve covers to the adapter, the required thread size is ¼” x 20 (length determined by thickness of the chosen valve covers).
The Taylor/Vertex valve cover adapters fit perfectly. All bolt holes (adapter to head and valve cover to adapter) align, with no need to fudge any of the holes (this, of course, depends on the heads that you’re using…always check carefully for clearance at the pushrod end of the rockers, and check for clearance between the adapter crossbars, where the adapter bolts are located, and the valve spring retainers). Granted, the inboard sides of the adapters (closest to the intake) overhang the heads a bit, but there’s no way around this to accommodate early-generation smallblock Chevy valve covers. During our initial fitting checks, using these adapters on the Trick Flow heads presented no problems at all. The adapters easily bolt to the heads and presented no clearance issues with our rocker arms. During test fitting on the BME Warhawk heads, we found that the inside of the upper area of the adapters would require a bit of clearancing due to the location of the rockers on these heads.
NOTE: The adapters tend to deflect a bit at the front and rear ends (as the adapters are tightened to the heads), possibly minimizing the adapter gasket’s ability to seal. Just as a precaution, I suggest adding a bit of RTV to the blue elastomer seal on each adapter, just at the front and rear sealing areas.
Because I chose to use the Taylor-Vertex valve cover adapters that allow mounting Generation 1 small block Chevy perimeter-bolt valve covers to LS heads, I obviously had a choice of a wide variety of valve cover styles (after all, we’re talking about the Gen I “old school” smallblock Chevy, where style choices abound). Since I planned to have the covers powdercoated and engraved, I chose a pair of relatively inexpensive cast aluminum flat-top style covers. I ordered a pair from Summit Racing, their P/N SUM-G3302. Both covers each feature a 1.220” hole (one for a breather and one for PCV). I had the covers powdercoated in a “silver splash” pebble-textured finish at Ace Powdercoating in Green, Ohio (“Silver Splatter PWB-3044 Wrinkle Prismatic”). The cost of powdercoating was $72 ($30 for material and $42 for labor). I then sent the covers off to my buddy, Art Carlton at Innovators West for engraving. Art engraves valve covers on a CNC mill, then colors-in the engraving in your chosen color. For the sake of identification and simplicity, I chose “408 LS,” with the engravings filled-in with orange-red paint to match the block color.
I installed the SBC valve covers to our Taylor adapters using ARP radius-nosed stainless studs (1/4×20 lower thread/1/4×28 upper thread) and 12-point 1/4×28 stainless nuts and flat washers. A cork/rubber valve cover gasket set (0.250”-thick) provides the seal.
The left side valve cover features a billet breather from Summit Racing. The right side cover features a billet adjustable PCV vale from M/E Wegner.
Our valve covers are cast aluminum “flat tops” that were powdercoated in a wrinkle finish and then engraved by Innovators West. I didn’t really need a tall profile for rocker arm clearance, but I preferred the appearance, given the overall theme of this build.
The satin wrinkle finish of the powdercoat (the particular finish is called “silver splash,” but appears as a dark charcoal) provides not only a tidy appearance but is easy to clean. The engraving of the text was filled in with red paint that matched our block.
I didn’t want to throw too many different colors into this build. The valve cover finish is attractive and a bit understated. At first glance, due to the over-the-top induction setup and the chosen valve covers, many folks might initially assume that this is a smallblock Chevy. That’s exactly the effect that we were after.
ADJUSTABLE PCV VALVE
For this build, we’re experimenting with a newly-introduced adjustable PCV valve from M/E Wagner (P/N DF-17). This innovative valve is adjustable for airflow for idle mode and can be set for fixed constant flow for engines with low vacuum signals (aggressive cams with lots of overlap, etc.). The benefit is to allow optimum scavenging, primarily in an idle and off-idle mode.
M/E Wegner’s billet PCV valve features fine-tuning adjustment to optimize vacuum primarily at idle and off-idle.
Frankly, even if you don’t feel like playing with the adjustability, the Wegner PCV valve looks way cool. We plumbed ours to the rear of the intake manifold using black braided -6 AN hose, with the ends of the hose skrink-tube sealed for a tidy appearance.
PRE-OIL ENGINE BEFORE FIRING
Whenever a fresh engine is to be fired for the first time, it is absolutely essential to pre-oil the engine by sending pressurized oil through the entire oil passage network. This insures that bearings, rockers, pushrods, etc. are lubricated before the engine is fired. A dry start can kill an otherwise properly-built engine. For this task, we used the new pre-oiler unit from Goodson, their P/N EPL-120. This aluminum canister holds 12 quarts of oil and features a very convenient carry handle, a pressure gauge, pressure pop-off safety valve, hose and a variety of fittings to accommodate a range of block oil port sizes. Simply fill the canister with fresh oil of the appropriate type/grade, connect the hose outlet to an oil feed port in the block, pressurize the canister with shop air, and open the unit’s ball cock valve. With valve covers removed, verify that oil is being delivered to the top end.
I can’t stress the importance of pre-oiling too strongly. Regardless of where the engine came from or who built it (DIY, pro engine builder, OE “crate”, etc.), YOU MUST ALWAYS PRE-OIL ANY FRESH ENGINE (or any engine that has sat dormant for an extended period of time, for that matter), prior to the first start. Don’t rely on simply cranking the engine in order to prime.
By the way, in preparation for a dyno run, or if you wish to use a conventional oil pressure gauge, you can make your own threaded adapter to take the place of the GM oil pressure sensor (GM P/N 12616646). The threaded hole in the top rear of the block features 16mm x 1.5 threads. You can either locate a hex head 16mm x 1.5 x 10 – 15mm bolt and drill through the bolt with an 11/32” dill, then tap the hole for 1/8” NPT. Or you can use junk/spare GM oil pressure sender….on a lathe, machine off the top of the sensor, down into the hex-drive sides, leaving about 3/16” depth at the drive flats. This will remove the “guts” of the sender top, revealing a flat recessed bare aluminum base at the top. Then (still on the lathe), drill an 11/32” hole all the way through the sender, and tap the top of the hole for 1/8” NPT. Using either a 16mm bolt or an old GM sender, you can now connect any oil pressure sender (electric or mechanical) that features a 1/8” NPT connection. Either way, the bolt or old sender must be fitted with a crush washer or aluminum/rubber Stat-O-Seal washer for sealing, since the 16mm threads are straight and will require sealing between the block and the adapter. If you use an old sender, make sure that the bottom of the hex and the threads are clean and free of surface irregularities. Of course, you can use a new sender to make your adapter, but a new one is pricey, to the tune of around $64. Just grab a used sender and machine it by cutting off the top, drilling through and tapping the top of the hole. If you started off with a core engine, chances are you already have a donor sender.
Goodson’s lightweight aluminum engine pre-oiler is the nicest one that I’ve ever tried. It’s slim, light, has a convenient carry handle, and is very user friendly. Just add a max of 12 quarts of oil, pressurize with shop air, connect to a convenient oil port in the block and open the valve. Pressurized oil is quickly delivered throughout the engine.
Prior to firing the fresh LS engine, we pressurized the oil system using the Goodson unit. We fed oil into the block via the top rear oil pressure sending unit port.
Since at this point we’re not concerned with a specific in-vehicle application, we chose exhaust headers that would temporarily serve as examples for an LS application. The Hooker black-ceramic headers were installed to the Trick Flow heads using a set of 8mm stainless steel studs, washers and 12-point nuts from Totally Stainless (these studs feature a very handy female hex for installation/removal aid). The Hooker header flanges fit perfectly to the heads…literally a drop-on installation (I love it when that happens). FYI: the headers that we chose for photos are designed for an LS engine application in a Tri-Five Chevy. Since we’re going to use the dyno shop’s headers for the engine dyno run, our initial choice of headers (for photos) was really immaterial. I simply thought that the long-tube headers shown here look great and dress the engine well. For the engine dyno run, we used a set of headers supplied by the dyno shop, already fitted with air/fuel ratio sensors.
Our Hooker Competition long-tube headers, installed primarily for photo purposes in this article, are actually designed for performing an LS engine swap into a 1955-57 Chevy application.
View of the right side. The fit of these headers to our engine was flawless. Literally a drop-on installation.
Thanks to the flexibility of the Lokar braided dipstick tube and it’s adjustable-pivot bracket, dipstick tube mounting presented no problems in relation to the header primary tubes.
A common area of potential clearance problems is between the LS water temperature sensor and an exhaust header flange. Ours cleared fine, but depending on the header brand you need to be aware of this, as you may need to grind a bit of material from the front tab of the flange.
On the right side of the block, the dipstick assembly was installed. For the sake of appearance, I chose a Lokar LS dipstick assembly that features a flexible stainless-steel-braided tube body and a billet aluminum dipstick knob. The dipstick tube assembly was too long to attach its upper bracket to one of the header studs, so instead of disassembling the dipstick tube, shortening the stainless braided tube and reassembling, I secured the Lokar bracket to an available 10mm x 1.5 thread hole in the head, above the exhaust header fastener area. I needed to enlarge the Lokar bracket’s bolt hole to 10mm, and installed the bracket to the cylinder head using an 8mm ARP stainless bolt and a ½”-long stainless spacer, to kick the dipstick out a bit to clear the valve cover. The lower portion of the dipstick tube assembly features an aluminum tip fitted with an O-ring. After lightly oiling the O-ring, the tube extension slid neatly into the block’s dipstick tube port. However, during test fitting, the dipstick tended to hang-up once fully inserted. Upon close examination, I discovered a nasty burr on the swedged-on tip at the end of the stick’s cable, and a burr on the lower opening of the dipstick tube. After dressing these areas, insertion and removal presented no problem.
The Holley oil pan features a 5.5 quart sump (6 quarts total with filter). Once I added 5.5 quarts to the sump, I checked the level witness mark on the dipstick tip and marked it for reference according to the oil level (using an electric etching pen).
Since we’re running this engine with carbs, we don’t need electronic management to control fuel, but we do need a system to control spark. The EASY way to accomplish this is with MSD’s LS ignition controller. They offer two versions: the 6LS, compatible with a 24-tooth crank reluctor, and the 6LS2, compatible with the 58-tooth reluctor. Our Callies crank came equipped with a 58-tooth wheel, so our ignition controller is the 6LS2.
The controller (which can be mounted anywhere in the engine bay within reach of the MSD harness) features six pre-programmed ignition curve plug-in “chips.” This literally provides a plug & play selection. If you prefer, you can create your own custom ignition curve using the supplied CD (plug the controller into a laptop or desktop PC with a USB cable, and follow the instructions).
The MSD harness simply needs to connect to the ignition coils, the engine’s water temperature sensor, cam position sensor and crank position sensor (you can also connect to a MAP sensor). That’s it. I’ve installed this MSD system several times, and it’s a piece of cake. This system makes converting an LS engine to carburetion so easy that it’s almost embarrassing. By the way, the MSD 6LS or 6LS2 controller will also work with a fuel injection setup, allowing independent control of the ignition curve.
The ignition coils (just like any LS platform, you need one coil per cylinder) are MSD’s P/N 82858. These are listed as applicable to the LS1/LS6, but work just fine with a 58-tooth reluctor and the LS2 style cam sensor. No issues at all.
One of the design aspects of this build focused on using early-generation smallblock Chevy valve covers and relocating the coilpacks. I’ve never met anyone who likes the look of four coils mounted on top of each valve cover. Even though the pretty red MSD coils look far better than the ugly black OE coils, I still didn’t want to clutter the valve covers.
NGK #4177 spark plugs (3/4” reach, tapered seats) were installed with an adjusted gap of 0.054”. With anti-seize applied to the threads, all plugs were tightened to 10 ft-lbs.
When you convert an LS engine to carburetion, you still need to control spark. using MSD’s ignition controller and available wiring harness makes this a piece of cake.
Depending on the vintage of your LS type engine, the crankshaft will feature either a 24-tooth or 58-tooth reluctor wheel (this provides the crank position signal for ignition control). The ignition controller unit must be matched to the existing reluctor tooth count. MSD offers both versions. The 6LS controller is matched to the 24-tooth reluctor, while the 6LS2 accommodates the 58-tooth reluctor.
The MSD ignition controller includes six pre-programmed plug-in “modules,” each with its own ignition curve (the curves are explained in the instruction manual). This makes it easy to choose the curve you want by simply plugging in the selected module.
Simply plug & play. If you prefer, you can map out your own custom curve using the supplied CD software. Simply connect the controller (via a USB cable) to your laptop or desktop computer and follow the prompts.
Why mess with OE ugly black coils when you can have quality-built and attractive MSD coils? Since our smallblock Chevy valve covers require relocating the coils, you have several choices, which will vary depending on the available location in your engine bay. The coils can be mounted to the rear of the cylinder heads (a bank of four coils per head), using aftermarket or fabricated coil mounting brackets. Or you could mount the coils to the firewall, or to the inner fenders, etc. For our engine dyno session (and since we didn’t have a particular vehicle application in mind), we simply paid the coils on a cart at the front of the engine, using full-length MSD 8.8mm spark plug wires.
MSD 8.5mm spark plug wires were obtained as P/N 32079. This set features both straight “multi-angle” and 90-degree spark plug boots and terminals, and a set of LS style coil boots and terminals (the multi-angle boots allow easy custom angle adjustment, from straight to almost 90-degree or anywhere in-between. The multi-angle boots would protrude out between the primary tubes (with adequate clearance), while the use of 90-degree boots would allow me to route the wires behind the headers. After experimenting with each style, I decided to go with the multi-angle ends at the spark plugs. For the dyno session, we simply placed our MSD coils on a cart that we parked immediately in front of the engine. After cutting off the 90-degree boots at the opposite end of the wires, I installed the necessary LS coil boots (supplied in our MSD wire kit). For future in-car installation, the coils can be mounted to suit the builder (via aftermarket or fabricated mounting brackets bolted to the rear of the cylinder heads, or onto the firewall or inner fenders, etc.)
We’re all now aware of the critical need for a high zinc phosphate content in engine oil for a flat tappet cam-equipped engine, for both initial break-in as well as long-term use. However, when running high lift and higher than stock valve spring pressures, even a roller cam engine will benefit from this, in order to provide high-pressure lubrication to valve stem tips. This can be accomplished by either using your oil of preference and adding a zinc phosphate concentrate (ZDDP), or by using a specialty engine oil that’s already formulated with this protection. This type of oil is now readily available from companies such as Brad Penn, Joe Gibbs, Royal Purple and others. For this application, I chose Brad Penn 20-50 break-in oil, high in zinc phosphate. Any performance engine, whether flat tappet or roller cam equipped, will benefit from this (and is absolutely critical for flat tappet break-in). Even though this engine features a roller valvetrain, I feel the need to remind readers about this issue. For break-in of a flat-tappet cam, it’s best to use a dedicated “break-in” oil that’s high in ZDDP. Following flat tappet break-in, as well as for high performance roller cam applications, long-term oil should contain appropriate levels of ZDDP.
OUR DYNO RESULTS
We recently ran the 408 LS engine on the engine dyno. The results: 670.5 HP at 6500 RPM and 581.7 lb-ft of torque at 4900 RPM. The dyno session was conducted at Gressman Powersports, in Fremont, Ohio, on their new Superflow 902S engine dynamometer.
Josh at Gressman Powersports sets up the shop’s dyno headers, equipped with air/fuel sensors in preparation for our runs.
Our engine was set up on Gressman’s new Superflow 902S engine dyno. Note that the water “steam” lines at the front of the heads are plumbed to the dyno’s water system.
With the velocity stacks mounted and the dyno air box in place, she’s ready to fire.
Scott Gressman fires the engine and controls initial test running from his isolated control station. After several short test runs to establish temperatures, oil pressure, fuel pressure, etc., the actual runs under load revealed our peaks at 670.5 HP at 6500 rpm and 581.7 lb-ft of torque at 4900 rpm. Additional tuning (via timing and carb adjustment) would likely yield an additional 10-15 HP, but given our time constraints of the shop’s busy schedule, we were satisfied with the results.
Gressman’s newly remodeled dyno room is even outfitted with an additional monitor, allowing him to keep tabs on data even if he’s inside the cell. Pretty cool.
Aside from playing with timing, no issues arose…no leaks, no mechanical glitches, etc. We ran the ignition via an MSD 6LS2 ignition controller, which (when plugged into a laptop) allowed dyno shop owner Scott Gressman to quickly adjust timing during the session. While we were satisfied with the results, we’re confident that additional testing time (messing with timing and carburetor tweaking) would likely provide us with an additional 10 – 15 HP, but we only had a specified amount of time allotted, since the shop had quite a few customers’ race engines waiting their turn on the dyno. Listed here are the horsepower and torque results summary during the final pull for both torque and horsepower. Ignition timing was 9 degrees cranking, 15 degrees at idle and (during incremental testing) was happiest at 26 degrees.
NOTE: One of my previous LS builds was virtually identical to this 408 engine, in terms of displacement, compression and valvetrain (same Trick Flow heads, and near-identical cam specs). The previous engine featured a near-stock bore (6.0L block overhoned by 0.005”) coupled with a 4.000” stroke, for 403 CID. The only big difference between the two builds was the fuel/intake system. The 403 CID engine featured a single plane intake manifold with a single 800cfm carb, while this current 408 CID build featured Holley’s Hi-Ram intake manifold and a pair of their 600 cfm Ultra HP carbs. The 403 engine pulled 625.4 HP, while the 408 engine pulled 670.5 HP, a difference of 45.1 HP. In addition to the added 5 cubic inches of displacement, the 45 HP gain can be attributed primarily to the Holley dual-carb setup.
RPM LB-FT TORQUE HP
3700 484.5 367.2
3800 495.3 383.9
3900 507.8 402.2
4000 520.7 421.3
4100 529.0 437.4
4200 539.5 455.5
4300 558.1 473.2
4400 559.5 491.1
4500 567.7 509.3
4600 574.6 525.8
4700 579.4 540.6
4800 581.5 553.2
4900 581.7 564.0
5000 580.8 573.9
5100 579.5 583.3
5200 577.2 591.7
5300 574.9 600.0
5400 571.7 607.2
5500 567.6 613.5
5600 565.2 621.3
5700 563.1 629.4
5800 562.0 638.5
5900 561.4 648.1
6000 559.0 655.8
6100 556.1 662.7
6200 549.9 665.6
6300 543.2 667.6
6400 536.3 669.1
6500 531.1 670.5
OUR LS 408 PARTS LIST
ENGINE BLOCK………………………..GM, 6.0L LQ9 Iron
MAIN CAPS………………………….….OE PM (powdered metal) CAPS
MAIN STUDS…………………….……..ARP, P/N 234-5608
MAIN BEARINGS……………………….MAHLE CLEVITE, P/N MS-2199HK
ROD BEARINGS (UPPER)………………MAHLE CLEVITE, P/N CB-663HNK
ROD BEARINGS (LOWER)……………..MAHLE CLEVITE, P/N CB-633HXK
CAM BEARINGS…………………………MAHLE CLEVITE, P/N SH-2125S
CAM BEARING INSTALLER TOOL……..GOODSON, P/N CBT-300
4.000” Stroke Compstar forged, 58-tooth reluctor, P/N AP031N-CS
CONNECTING RODS……………………CALLIES, 6.125”, Compstar forged, P/N CSC6125 DS2A2AH
PISTONS………………………………….JE flat-top, FSR, Asymm, 4.030” bore, 1.115 CD, P/N 311979
CYLINDER HEADS (ASSEMBLED)…….TRICK FLOW P/N TFS-3061T001-C02
(HEADS ACTUALLY USED ON DYNO)
(OPTIONAL HEADS IN BARE FORM)……………BILL MITCHELL PRODUCTS
WARHAWK, LS1, 235cc Int; 72cc chambers, P/N 001-025250
THREADED BLOCK PLUGS (X3) 16mmX1.5……….GM, P/N 11588949
THREADED BLOCK PLUG, 28mmX1.25…………….GM, P/N 12561663
FRONT OIL GALLEY CUP PLUG……………………..GM, P/N 9427693
REAR OIL GALLEY PLUG BARBELL (15mmX64mm)….GM, P/N 12573460
CYL. HEAD DOWELS (X4)………………………….…GM, PN 12570326
OIL PRESSURE SENSOR………………………………GM, P/N 12616646
WATER TEMP. SENSOR……………………………….GM, P/N 12608814
CRANK POSITION SENSOR (FOR 58 TOOTH)………GM, P/N 12585546
CARBURETORS (X2)…………………..…..HOLLEY 4150, 600 cfm, P/N 0-80801-RD
INTAKE MANIFOLD…………………….…HOLLEY HI-RAM, P/N 300-226
INTAKE MANIFOLD TOP…………………HOLLEY P/N 300-216
INTAKE MANIFOLD BOLTS
(TO HEADS)………………..…TOTALLY STYAINLESS, 8mm X 1.25 X 80mm SHCS
UPPER PLENUM TO INTAKE MANIFOLD BOLTS… TOTALLY STAINLESS,
1/4X20 X ¾ SHCS
CARBURETOR LINKAGE………………………………HOLLEY, P/N 4022
CARBURETOR VELOCITY STACKS………..CP PERFORMANCE P/N 620-60445
VELOCITY STACK STUD KIT………….…ALLSTAR P/N 26056 (studs cut to length)
VELOCITY STACK STUD NUTS………….CAM MOTION TOP SEAL (1/4X20 threads)
RED 5/16” ROD ENDS (for main throttle shaft)……..…..QA1 P/N AMR5
VACUUM FITTING FOR PCV…………………….……EARL’S P/N 984206ERL
VALVE COVER BREATHER………………..….SUMMIT RACING, P/N SUM-G3403
VALVE COVER BREATHER GROMMET……..MOROSO P/N 68772
PCV VALVE GROMMET…………………….….MOROSO P/N 68775
OIL PUMP…………………………………………MELLING hi-volume, P/N 10296
CRANKSHAFT DAMPER…………….…………..FLUIDAMPR P/N 740111
CRANKSHAFT DAMPER BOLT…………….…..ARP P/N 234-2503
(16mm X 2.0)
CYLINDER HEAD STUDS……………………….ARP, P/N 234-4316
EXHAUST HEADERS……………………..HOOKER, black ceramic, P/N 2292-3HKR
HEADER FLANGE STUDS……………….TOTALLY STAINLESS 8mm X 1.25 X 40mm
CYLINDER HEAD GASKETS………….…MAHLE VICTOR, MLS, P/N 54445
GASKET SET………………………..……..MAHLE VICTOR, P/N CS5975
ENGINE PRE-OILER/PRESSURE UNIT……………..GOODSON, P/N EPL-120
CAMSHAFT………(HYD. ROLLER)……………….COMP P/N 54-462-11
PUSHRODS (5/16” X 7.500” X 0.080” WALL)……..COMP CAMS P/N 7957-16
LIFTERS…(SHORT/RACE-HYD)……………….…..COMP P/N 15850-16
LIFTER GUIDE TRAYS ………GM P/N 12595365 (GEN IV) OR 12551162 (GEN III)
(EITHER STYLE FITS THE LQ9 BLOCK)
NOTE: DRILL OUTBOARD SIDES FOR BETTER OIL DRAIN
(FOR BMP HEADS)……….. 2.080” X 5.300” X 5/16” BMP P/N 702830RM
(FOR BMP HEADS)…………………..1.600” X 5.300” X 5/16” BMP P/N 702715SD
VALVE SPRING KIT
(FOR BMP HEADS)………………………COMP 26926TS-KIT
ROCKERS (rollers; 1.7:1 ratio)………..…..HARLAND SHARP P/N SHLS17
OIL PAN…………………………………….HOLLEY, cast aluminum, P/N 302-1
OIL PAN BOLTS………………………..….ARP, P/N 434-6902
OIL FILTER…………………………..…….AC DELCO PF48 or equivalent
TIMING SET……………………..…………CLOYES P/N 9-3172A
CAM GEAR BOLTS……………………….ARP P/N 134-1003
TFS TIMING CHAIN DAMPER (LS2 STYLE)……….TFS-30675540
TFS TIMING CHAIN DAMPER ADAPTER…………..TFS-30675600
CAMSHAFT RETAINER PLATE BOLTS…..ARP P/N 134-1002
WATER PUMP……………………………MEZIERE P/N WP319U
WATER PUMP WATERNECK…………..MEZIERE P/N WN0019U
WATER PUMP BOLTS (6)……….TOTALLY STAINLESS 8mm X 1.25 X 115mm
FRONT COVER (OE)…………………..GM, LS2 (w/cam sensor) GM P/N 12633906
FRONT COVER (COMP)…………………COMP CAMS P/N 5496
FRONT COVER BOLTS………………….ARP P/N 434-1502
REAR COVER……………………………..GM P/N 12633579 (P/N 12639250 KIT)
REAR COVER BOLTS…………………….ARP P/N 434-1504
VALLEY COVER……………..BIRCHWOOD, FABRICATED (0.250-thick aluminum)
VALLEY COVER BOLTS (12)……….TOTALLY STAINLESS 8mm X 1.25 X 20mm
ENGINE BLOCK PAINT………….CHEVY ORANGE-RED (Dupont base/clear)
SPARK PLUGS………………………………….NGK 4177 or equivalent
VALVE COVER ADAPTERS………………………TAYLOR/VERTEX, P/N 555701
VALVE COVERS…………………………………..SUMMIT P/N SUM-G3302
PCV VALVE………………………………..M/E WAGNER, billet adj., P/N DF-17
PCV VALVE HOSE……………………….. –6 black braided (w/shrink tube ends)
OIL COOLER ADAPTER KIT……………….LINGENFELTER P/N L300025297
STEAM HOLE FRONT FITTINGS (-4 AN)……………TFS-30600611
STEAM HOLE REAR CAPS……………………………TFS-30600612
FRONT STEAM PLUMBING………..Two –4 90-deg hose ends; two –4 straight hose ends, -4 T-fitting, -4 black braided hose
FUEL LINES………………………………………….. 3/8” OD aluminum, fabricated
FUEL LINE FITTINGS…………………………..…. –6 tube nuts and ferrules
FUEL MANIFOLD……………..……..PETERSON, P/N 10-0071 (5-way –6AN/-10AN)
FUEL MANIFOLD BRACKET……………..BIRCHWOOD (fabricated aluminum)
37-DEGREE FLARING TOOL…………….FRAGOLA, P/N 900500
IGNITION CONTROLLER………………..MSD P/N 6LS-2 (for 58-tooth reluctor)
IGNITION COILS……………………………MSD P/N 82858
SPARK PLUG WIRES……………………….MSD P/N 32079
DIPSTICK ASSEMBLY……………………LOKAR P/N 5008
TIMING POINTER………………………….TCI P/N 871005
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