Mike huff please help

[bluecmaro96]

I have the ssm powerpack and also have my heads milled .020 the machine shop guy put in stock compression pistons, since my cr isnt stock anymore will having stock cr pistons hurt my performance in the 1/4 mile? would i have gained any et if he would have put in higher cr pistons? to match the cr i currently have? thanks mike

[Ironman24]

OK, just wanna make sure I got this right. You had your motor rebuilt and the machine shop used the stock compression pistons?

Stock compression is 9:4:1 and with your heads milled .020 that will bump you up to about 9:7:1 or 9:8:1. You are already going to gain performance with the milled heads, a higher CR piston would have raised performance more but the stock pistons are not "hurting" you. I don't know how much compression we can run on pump gas. Anyone know?

[bluecmaro96]

Yes the shop used stock cr pistons, since my cr is around 9:8.1 from the heads being milled and the machine shop used 9:4.1 pistons, that wont make my cr go down? So being that i have 9:8.1 compression and i have 9:4.1 pistons my cr is still 9:8.1? Would i have gotten a noticeable gain from getting pistons that match my cr 9:8.1 pistons? thanks again mike i greatly appreciate your help [img]graemlins/thumbsup.gif[/img]

one more thing am i right about this? Ok with the heads milled and all i have around 9:8.1 cr and that was with stock cr pistons, so if i get aftermarket pistons but with the same cr as the stock pistons i will still have 9:8.1 cr right? Now if i would have gotten pistons that wree matched with my current cr which would be 9:8.1 would that have upped my cr? and again any actual noticeable gains? thanks again, sorry for being a pita

[Ironman24]

You can change your compression by bringing the heads closer to the piston, as you have done already. Or you can change the compression by changing the dish on the piston, or changing the height of the piston. Using a stock piston won't lower your compression ratio.

Yes if you were to have got some aftermarket pistons that would raise your CR to 9:8:1 and then added your milled heads then the compression would be even higher, over 10. I need to clay my motor and find out how much piston to valve clearance we actually have.