632 Mountain Motor (Part 1A)

We build a big, big block drag mill

just for the sheer hell of it.

by Mike Mavrigian

photos by author

632-01

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

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