Compression ratio

[71scamp78]

Stock block la 360 with unknown flat top pistons with valve reliefs. Heads are J heads with 2.02 valves with stock chambers. Not sure what they mostly cc at. Im assuming with the pistons .045 in hole and open chamber heads the compression has to be low. Just curious because I'm wanting to install a whiplash cam and it says 8.6 to ratio is ideal.

 

[33IMP]

I'm sure there are guys here that can give you a very educated guess (assuming a bunch of measurements and volumes that have to be accurate for a REAL number). If you were asking about a 440 I could help better.
But for an off the wall guess...... I'd guess you are at a low 8 comp ratio. (from a very UNeducated on small blocks guy).

 

[71scamp78]

Yeah I'm guessing somewhere in that 8.5 range

 

[dirty white boy]

ran your numbers on a wallace calculator with a .041 thick gasket comes up to 8.7 compression ratio... but thats guessing at combustion chamber cc's and valve relief cc's, need accurate measurements!!

 

[71scamp78]

ran your numbers on a wallace calculator with a .041 thick gasket comes up to 8.7 compression ratio... but thats guessing at combustion chamber cc's and valve relief cc's, need accurate measurements!!

Yeah my guy hasn't cc the heads yet. Appreciate the estimate

 

[aaronk785]

Sounds like you might have speed pro 405 pistons. They’re usually about .050 in the hole with 4 valve reliefs. In my 360 they were .050 down. With a .028 gasket it came out to be about 8.8 to 1. I don’t remember the head cc though. J heads with 2.02 valves. It ran very well with a mopar 280 474 cam.

 

[aaronk785]

Ran fine on 87 fuel.