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

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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