12480050 - Bowtie Chevy Small Block - 3.980"-4.190" Bore, 8.700" Deck, 2.30" Mains, 4 Bolt Main, Siamesed Bores - DISCONTINUED
This product may require vehicle validation(s) for proper fitment. Please contact us to confirm correct vehicle fitment and usage.
GM Performance Parts Race Blocks
Our blocks take the guess work out of what block you need to make big horsepower - that is competition tested in NASCAR BUSCH and NHRA competition eliminator! Only GM Performance parts can offer you such a huge selection of race blocks that have been precision CNC machined with tighter tolerances than our Bowtie blocks. These blocks feature full race prep machining, 4 bolt splayed main caps, and the very highest grade materials throughout. When your competition has spilled thier guts all over the racetrack, you'll still be in the show thanks to your GM Performance Parts race block.
Notes for all race blocks:
- Machined to .001" tolerances
- Cylinder decks, front and rear of case, oil pan rail surfaces and head dowel pins are blueprinted!
- Non standard cam bearings required (see notes below for details)
- Cam bosses are enlarged to allow machining for the use of larger cam bearings
- Extra thick main bearing bulkhead machined at 5 drgrees
- Premium quality studs and SAE 8620 steel main bearing caps
- Billet wet sump rear main cap can be adapted to dry sump with plugs
- Bearing cap inner bolts are spread .210" to allow machining for the use of 400 journal crankshafts
- Priority main oil system
- 2-piece rear main crankshaft and pre-1986 oil pan required
- Extra thick deck surfaces with blind tapped head bolt holes for improved head gasket sealing
- Cylinder bores have a nominal wall thickness of .340"
- .225" minimum xylinder bore wall thickness at 4.155" bore, sonic bore test data sheet included with each block
- These blocks may require clearencing of the tops of the lifter bores for some aftermarket mechanical roller lifters
- Lifter valley oil scavenging boss behind cylinder #8 below bell housing flange is not drilled and tapped
- Oil dipstick holes are not drilled
Specifications for this block:
- CNC cast iron competition block designed for drag racing, road racing or restricted oval track racing
- 4 bolt SAE 8620 steel mains, 20 degree splayed caps on center three mains
- 8.700" deck can be machined to 8.500" deck height
- Camshaft tunnel is raised .433" to 4.955"
- Cam bearing bores machined for 2.250" OD X 1.875" roller bearings
- 3.980" rough bore
- 4.190" max bore (will yield minimum of .250" cylinder bore wall thickness)
- Siamese bores
- integral oil restrictors
- Must use big block water pump, must raise water pump with adaptors if using balancers larger than 6"
- Old's Aurora V-8 bellhousing bolt pattern (12.25" max flywheel diameter)
- Lifter holes and cylinder head bolt holes are not machined
- Will accept standard, SB2.2 and splayed lifter patterns
- Can be machined to accept any small block Chevy cylinder head
- Machined as 4.00" bore and main centers, can be machined to 4.500" bore centers
- Shorter than production pushrods required
- Tested to over 800 HP
- Item Requires Shipping
- 273.0 lbs.
- W28.0000” x H17.0000” x L19.0000”
- FREE 48 State Shipping
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