Less weight and the same great horsepower are the benefits of a GM Performance Parts Aluminum Race Block. GM Performance Parts Aluminum Race Blocks provide the same competition-level strength and reliability of our cast-iron Race Blocks, but their lighter weight improves chassis dynamics. The super-tough A-356 aluminum competition blocks are CNC-machined to +/- 0.001-inch tolerances. GM Performance Parts Aluminum Race Blocks are ideal for road racing applications or high horsepower turbocharged engines.*

GM Performance Parts Aluminum Race Block Technical Notes:
Extra-thick deck surfaces with blind-tapped head bolt holes for improved head gasket sealing
Centrifugally spun cast-iron cylinder sleeves
Blueprinted cylinder decks, front and rear of case, oil pan rail surfaces and head dowel pins
2-piece rear-main crankshafts and pre-1986 oil pans required
Enlarged cam bosses allow machining for larger cam bearings
2.000" O.D. (1.867" I.D.) cam bearings P/N 12370843 required
Blocks may require clearancing at top of lifter bores (0.842") for some roller lifters
Timing system clearance should be checked before engine assembly
Extra thick main bearing bulkhead machined at 5°
Premium main studs and SAE 8620 steel main bearing caps
Priority main oiling system
Billet wet sump rear main cap can be converted to dry sump with plugs
Oil dipstick holes not drilled

* Proposed applications have not been specifically tested or validated by GM Performance Parts.

A-356 aluminum competition block
CNC-machined
Siamesed bores with increased wall thickness
4.117" rough-finished bore
4.135" maximum bore
3.750" maximum stroke
Splayed 4-bolt steel mains
400 main size
Dry sump use only
Tested to more than 800 horsepower!