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

falconsfan

ive read some threads stating you can but it changes the compression ratio if youre using stock 350 pistons?
Maybe someone with "the know" will post as I have a chance to pickup some 455 heads for my 350 and would like to know the answer as well.

captjim

They physically bolt on, but will seriously lower the CR over the older 350 heads. And you can get the same size valves in a SBO head. Also, you will have intake issues, I believe you will need to port match an RPM, but not positive about that.

joe_padavano

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).

Pghstarsky

Interesting, thank you so much for your prompt response.