Did a compression test

[mjb765]

70 383/335 just did a compression test. all the cylinders register about 125PSI....is that OK or should it be more?? From what I remember it's all ok as long as they are close to the same. no smoke out the exhaust and the plugs looked good. Just making sure the motor is OK before I start making mods.....

[Chryco Psycho]

You are fine , even compression is basically more important then the actual # unless they are all about #30 !!
Cranking compression can vary due to cam design , combustion chamber size etc, I have seen engines anywhere from 90psi to 190

[mjb765]

You are fine , even compression is basically more important then the actual # unless they are all about #30 !!
Cranking compression can vary due to cam design , combustion chamber size etc, I have seen engines anywhere from 90psi to 190

Cool...that's kind of what I thought...just can't remember the last time I did a compression test on one of these motors.

Thanks for the info. 

[Chryco Psycho]

 

[chargerdon]

My 66 Charger with 383 4v .030 over mild cam will read around 130 psi...   (Mopar advertised them as being 10:1 static compression, but that's bullshit.   Do the math and you will find it will read 10:1 IF IT HAD NO GASGET..  With normal gasket more like about 9.2 to 1 static.

My challenger 360 LA with 408 stroker kit was built to be around 9.8 to 1 static, and cold it will read around 190 psi per cylinder.   

[Chryco Psycho]

Are you basing that on cyl pressure ?
14.7 atmospheric pressure x 10  would be 147 psi . Cam design can bleed off or trap more pressure so 10"1 with a longer duration cam can read lower .

[Racer57]

Imho compression checks are almost worthless. Leakdown tests are better. A pain in the azz to do, but they can tell you everything you need to know.