Quote:
Originally Posted by Pghstarsky
Will 455 heads fit directly onto a 350 block? I dont think they will but I overheard someone talking about how it would work. Thanks
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Yes, all Olds heads are the same size and bolt pattern. 77-up small blocks use 1/2" head bolts vs. 7/16" on 76-older blocks. You can drill early heads for the larger bolts.
As others have noted, big block heads have 80cc chambers vs. 64-ish chambers on 70-earlier SBO heads. The BBO heads also have larger ports that a street-driven 350 will be hard-pressed to use. The Performer RPM and some factory intakes are the only ones with enough meat to port-match to the BBO ports. Failing to do this matching will negate any flow benefits. As others have noted, simply maching the SBO heads for the big block valves is a much cheaper way out (and is what the factory did on the W-31).