ok, swapping the 305 out and putting in a 355 i'm currently assembling. I just figured the compression ratio to 11:1. I have aluminum heads. Is this too high compression for premuim (93) pump gas? or should I be ok?

 

Depends on the cam you have, but 11:1 should be ok... very borderline, but should be ok.

 

cam is: 224int/231exh duration at .050. .520int/.515exh lift, 113 degree lobe separation, computer controlled cam, from the comp cams new XFI line.

 

I don't have much experience with computer controll, but judging by that cam, 11:1 might be kinda high... If possible, a cam with more duration and overlap would help alot. Whats the manufacturer's rec'd compression ratio for that cam?

 

it's a hydraulic flat-tappet cam btw, forgot to mention that. I'll hafta look up the recommended CR and post when i find it.

 

You want a roller cam, not flat-tappet.

 

it's not a roller motor, it's a 77 SBC 350 bored .030 over.

 

It's a little too high for pump gas. I'd go 10.3:1 max.

 

well I'm screwed then, unless i get different heads.

 

Not necessarily... what head gasket thickness did you use in the formula when you got 11:1 CR? Using a thicker one can drop CR quite a bit. 10.5 CR would be fine with the right cam and aluminum heads.

 

i used .041 gasket in my calculations. how much thicker do they come?

 

ok, i found some gaskets to put me right where i need to be, I was only looking at fel-pro before, thx for pointing me in the right direction, Air-Adam, you're officially my new automotive hero.