Chevrolet Performance 350 Main NASCAR Busch Series Block


– CNC’d to +/-.001″ tolerances
– Cylinder decks are blueprinted
– Non-standard cam bearings required
– Cam bosses are enlarged

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Chevrolet Performance 350 Main NASCAR Busch Series Block

– CNC-machined, cast iron NASCAR competition block
– 9.025″ deck height
– 4-bolt NASCAR-block specific steel mains, 17° splayed caps on center 3 mains
– 4.116″ rough bore
– 4.185″ max bore (siamese bores)
– Machined for 2.280″ cam bearings
– .875″ lifter bores
– -06AN water drains
– 45° -10AN front oil feed and valley scavenge
– AN O-ring pipe plugs
– (4) Center lifter valley drains (drilled & tapped)
– Steam holes drilled between cylinders .750″ below deck surface
– 1/2″ NPT water hole on each side of block
– Dry sump only (no oil filter boss)
– Tested to over 800 horsepower!

GM Performance Parts Race Block Technical Notes:
– These blocks are CNC’d to +/-.001″ machining tolerances!
– Cylinder decks, front and rear of case, oil pan rail surfaces and head dowel pins are blueprinted!
– Non-standard cam bearings required (see each block for details)
– Cam bosses are enlarged to allow machining for the use of larger bearings
– Extra thick main bearing bulkhead machined at 5°
– Premium quality main studs & 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 0.210″ to allow machining for use with 400 journal crankshafts
– Priority main oiling system
– 2-piece rear-main crankshafts & pre-1986 oil pans 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″
– 0.225″ min. cylinder bore wall thickness at 4.155″ bore, Sonic bore check data sheet provided
– These blocks may require clearancing the top of lifter bores for some aftermarket mechanical roller lifters
– Timing system clearance should be checked before engine assembly
– Lifter valley oil scavenging boss behind cylinder #8 below bell housing flange is not drilled & tapped
– Oil dipstick holes are not drilled

Note: CNC or computer numerical controlled machining is an automated machining process that guarantees exact tolerances. No one offers as many CNC-machined blocks as GM Performance Parts! No one. Splayed main caps have additional material holding the crankshaft in the block. This makes it even more unlikely that you’ll throw the crank through the oil pan.


Our race blocks take the guess work out of what block you need to make big horsepower. They are competition tested in NASCAR, BUSCH, and NHRA Competition Eliminator! GM Performance Parts offers you a huge selection of race blocks that have been precision, CNC-machined with tighter tolerances than our Bowtie blocks before you even get them. These blocks feature full race-prep machining, 4-bolt splayed main caps, and the very highest grade of materials throughout. When your competition has spilled their guts all over the racetrack, you’ll still be in the show thanks to your GM Performance Parts race block!

Prop65WARNING: These auto parts can expose you to chemicals including phthalates and lead. Installing or using these parts can expose you to other parts containing these chemicals and to engine exhaust, which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to