Aluminum cylinder heads sold in pairs only or 454 & 502 cu.In big-block GM applications.
Custom engraved with Sierra High-Performance logo
320 cc intake runner/119cc exhaust runner
2.25 intake/1.88 exhaust stainless steel valves
5 angle valve seat cut
Up to 65HP increase over OE cylinder heads
Suitable for use on Mark IV, Gen V, & Gen VI GM blocks. Must use correct corresponding head gaskets
Std. BBC 7/16" rocker studs and 3/8" diameter pushrod guideplates18-4506
Rectangle intake ports GUIDE PLATES
Use on factory non-adjustable valve train applications require adjustable rocker arm assemblies such as Sierra's 18-4507
Uses Sierra 18-4506 guide plates to utilize factory 5/16" pushrods
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