how much power in an guestimate would you say a 9:7:1 engine could gain going to somewhere in the high 10 to a max 11:1 area? just a rough percentage more or less.

 

Not much.

 

so how much performance potential is more compression worth?
for example, im looking to get a 350 for my currently 305 camaro. my question is, would i benefit by using the 305tpi heads i have in the garage on the new 350 as opposed to the stock heads that might be on it?

 

Cmpression gains you next to nothing for power on it's own. What it does is give you enough cylinder pressure to run a larger cam that will give you the hp increase.

It's actually more involved than that but you get the idea.

 

IIRC it's somewhere around 2% increase for each point of compression, so not much.

 

It is my understanding the gain in performance is not linear. The biggest jump with no other changes is from 8:1 to 9 1/2:1 with the increase being about 5%. After that, the increase becomes smaller incremently.

Redline: Another very important factor is the port volume of your 350 heads versus the 305. If the port volume is significantly smaller with the 305 head, you could actually lose power. The loss is breathing would not make up for the gain in compression.

 

gotcha, thanks