632 Mountain Motor (Part 1A)

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