Compression ratio

[Andrew]

Almost finished with 500 stroker 6 pack build. I'm trying to decide what compression ratio to go with. The heads are eddy rpm's, the cam duration is .231/.239. From what I understand felpro gaskets can put me at 10.4:1 or 10.1:1.

Can someone tell me how much difference this will make and how risky it is running 10.4:1 with my setup??? It is mostly a street car and though I want power, I don't want to worry about overheating or detonation.

 

[Red63440]

You sort of answered your own question, go with 10 to 1.

 

[Cranky]

Aluminum heads? Go for the 10.4. Aluminum sluffs off a bunch of heat in a hurry and they will work fine with more compression....unless your cam has a late opening on the intake and then it will pack the cylinders full and raise your cylinder pressure a lot. It's not so much static compression you have but how much cylinder pressure the cam creates in the lower rpm range. It's possible to make an 8-1 motor ping it's *** off and it's also possible to make a 11-1 engine run on pump gas. The cam dictates a huge portion of this.....

 

[Andrew]

Cam card says intake opens 9.5 btdc and closes 41.5 atdc. Its a Lunati hyd roller #60312. I tried pasting the cam card, but it didn't work.

 

[Mopars & Missiles]

Aluminum heads? Go for the 10.4. Aluminum sluffs off a bunch of heat in a hurry and they will work fine with more compression....unless your cam has a late opening on the intake and then it will pack the cylinders full and raise your cylinder pressure a lot. It's not so much static compression you have but how much cylinder pressure the cam creates in the lower rpm range. It's possible to make an 8-1 motor ping it's *** off and it's also possible to make a 11-1 engine run on pump gas. The cam dictates a huge portion of this.....

Agree with Cranky, 10.4/1 with aluminum heads will be fine on pump gas. Could go to about 11.0 on pump gas.

But with build "almost finished", this should have been determined long ago anyway.

 

[Meep-Meep]

Another vote for higher CR with the aluminum heads. I'm running 10.1 with iron heads and 190 PSI and it's just past the threshold of 91 pump gas. It runs OK for driving around but will ping if you lean on it hard. 93.5 seems to be the right answer for me but more testing will need to confirm this.