77 T/A Olds 403 heads 305 heads

[Pvt_Murphy]

Backround for the T/A 6.6 engine pontiac just took it's regular 350 heads and bolted them onto the Pontiac 400 engine with slightly more agressive cams. This boosted compression ration from ~ 7.6:1 to 8.1:1

I'm want to Bolt on an Edelbrock 3711 Intake Manifold (only one that allows shaker scoop to clear hood) and I'm considering, since there are no aftermarket heads that do the job, to score a set of preferably rebiult Oldsmobile 350 heads and bolt those on. The thing is, the Olds 403 had a stock Compression Ratio of 8.0:1.

so here are my questions:

1)Should I keep the current heads and rebuild em with performance parts? and just go for cams and such?
2)Are there any special considerations I need to be aware of?
2)What compressoin ration can I expect?
3)What Octane should I run for that compression ratio?

[MrPbody]

Pvt. Murphy,
You have several avenues to get where you want to be. We have successfully grafted 455 Olds heads to the 403. You must open the headbolt holes to the 1/2" size. Mill them .060" to get the chamber volume down. That will require the intake to also be milled accordingly, to assure port alignment.
Comp has a very nice kit to eliminate those bridged rockers, and have a fully adjustable valve train. Comp also supplies the leading-edge street cams of today, with their Xtreme Energy series. We use XE262H for mild builds in the Olds.
A rule of thumb for octane is to multiply your compression ratio by 10. Example: 9.2:1, multiplied, makes 92. Therefore, 92 octane SHOULD suffice for this ratio. Not all engines are exactly alike when it comes to reaction to compression, so be a bit conservative, rather than err too high.
FWIW

[Pvt_Murphy]

Thanks, wasnt sure where best to post the question.

I think I'm gooing to go with a fairly mild set up at the moment. I just Ordered an Edelbrock 3711 Manifold and I'm gonna get the matchig cam #3712, and I think I'll just replace the springs on the heads for now. I'll consider a much more agressive set up after I do my exaust, I'll also need a higher cfm carb and I'll put in an MSD igitoin system.