Dart Big M Sportsman Engine Block Big Block Chevy 4.500" Bore, 10.2" Deck Height
- Part # 31223454
- Material: Superior Iron Alloy
- Bore: 4.500"
- Bore & stroke: 4.625" x 4.750" (max recommended)
- Cam bearing bore ID: 2.120" Std.
- Cam bearings: Coated, grooved, w/3 oil holes PN# 32210030
- Cam bearing O.S. +.010", +.020", +.030" available *Call for Part numbers
- Cam bearing press: .002" Camshaft position: Standard or +.400” (Option / Big M²)
- Cam Drive: Timing chain, Gear drive & Belt drive
- Cam Plug: Standard BBC 2.215" P/N: 32520000
- Cubic Inch: 632" (Max Recommended)
- Cylinder Wall Thickness: .300" min @ 4.625" bore
- Deck Height: 10.200"
- Deck Thickness: Adequate for all applications
- Dist. Tap Hole Valley: None
- Fuel Pump Boss: Mechanical pump provision
- Fuel Pump Pushrod: Std. BBC
- Freeze Plugs: Std. Press in cup plugs 1 5/8 “dia.
- Head Bolt Pattern: Std. BBC Big M Bolt Pattern
- Inside Head Studs: P/N: 64210240 (Not included)
- Lifter Bores: BBC .8427" - .8437" + .300 Taller Gen V, VI style
- Main bearing size: Std. BBC
- Main bearing bore: 2.937" – 2.938"
- Main caps: Ductile Iron (Sportsman) 4 bolt
- Oil system: Wet or Dry Sump - Main Priority Oiling
- Oil Galley, main: Stepped, 9/16" – 1/2" – 7/16"
- Oil Cooler Holes: None (Can use aftermarket inline)
- Oil Galley, filter main: 5/8"
- Oil Filter: Stock oil filter location
- Oil Pan: Std. BBC bolt pattern & Stroker pattern at mains
- Rear Main Seal: STD 2 pc seal / Felpro# 2918
- Hyd. Roller Provisions: None
- Serial No. On main caps / Front passenger side below deck
- Starter: Mounts in standard location
- Stud & bolt holes: Blind tapped
- Tapped Holes: Std. English Thread & Pitch
- Timing chain / gears: Std. BBC
- Timing Cover: Gen IV / V stock 10 bolt cover or Dart +.400” Aluminium cover P/N: 67240002 (Includes Gasket)
- Torque Specs: All ½" bolts – 100 ft lbs w/CMD #3 high pressure lube
- Weight: 4.500" bore (260lbs)
About the Dart Big M
Dart engineered the Big M to be the strongest, most reliable, and easiest to build big block on the market.
With deck heights of 9.800” and 10.200” and bore sizes up to 4.600”, the Big M gives you the versatility to build a wide variety of engine combinations.
The Big M is fitted with Billet Steel 4-bolt main caps for ultimate bottom end strength. The Sportsman block is fitted with Ductile Iron 4-bolt main caps.
• Standard 9.800” and tall 10.200” deck heights.
• Standard 4.250”, 4.500”, 4.560” or 4.600” bore sizes with siamesed extra thick cylinder walls to resist cracking and improve ring seal (minimum .300” thick with 4.625” bore).
• Uses +.300” tall Gen VI style lifters. Modification for Gen IV style available.
• 4-bolt main bearing caps in Ductile Iron have splayed outer bolts for extra strength.
• True priority main oil system lubricates the main bearings before the lifters. Our stepped main oil gallery (9/16“ to 1/2“ to 7/16“) increases the flow of oil to the crank at high RPM, and our front oil crossover eliminates internal oil leaks around the distributor shaft.
• Lifter valley head stud bosses prevent blown head gaskets.
• Dual oil pan bolt patterns fit standard and notched oil pans.
• Big M Sportsman: Parts kit sold separately. 32000002