I see that 2.8's have 8:9:1 compression but 3.1's have 8:5:1 why is that? How can i get 9:1:1 compression on the 3.1 without a rebuild/changing pistons? Reason why i want this compression because the cam im getting maximum compression is 9:1:1 w/ 212 duration and .440 lift. Im building the 3.1 up for a turbo figure i can run alot of psi with that compression ratio and the cam will perform well.

 

i know w small blocks you can shave the head a few thousandths to boost compression,,,,,,,,but i've never plastiguaged a 2.8/3.1/3.4 to see how much room there is

 

if you're going turbo why raise compression? all that will do is lower the amount of boost you can run . . . turbo's are more efficient at compressing the air than engines, so have the turbo do all the work.

 

reason i want to do this is so i can run this cam i want, i wont have a turbo on this car for atleast two years.

 

do you have a link to the cam? chances are it will run fine with 8.5, especialy if it says max rec cr is 9.0 . . . its just a shame to go to all the work to raise cr, best way is usually by changing pistons, otherwise you mess up the combustion chamber design. although on our crapilly designed heads that probably isnt really a problem, so wth.

methods include milling the heads, and thinner/thicker head gaskets. other than that youre pretty much stuck with changing pistons, which isnt worth the trouble for that cam.

the 3.1's have different comrpession because the stroke changed, requiring a piston change. why gm lowerd it to 8.5 i cant tell you, but a lot of the things they did to the iron head motors are widely regarded as bad moves, so whats new.

 

This is the cams part number that i want to use CCA-K16-233-4

 

you're totally fine with 8.5 cr. you can raise it a bit to make a few extra hp,(like 3 or 4), but at this point its not worth it, especially if you are even thinking about turboing it later on. if you were going up to like 10:1 then it would be worth it, but otherwise not really.