Head question??

'teen machine said

So by my calculations a 318 with .030 thick head gaskets and 62cc heads makes around 8.5:1 compression.

The same engine with 72cc heads makes around 7.8:1.

I've heard lots a guys say putting 360 heads on a 318 will drop you compression to 6-6.5:1.

Even 84cc heads make over 7:1!

Click to expand...

What calculator are you using to come up with those figures and what head gasket bore are you using and are you accounting for valve reliefs and/or dished pistons? I ask because using this calculator

http://www.csgnetwork.com/compcalc.html

which seems consistent with all others I've used, figuring a .039" thick head gasket with a 4.08 bore (std. replacement head gaskets currently available as a regular order), 10 cc's for valve reliefs (no dish), pistons .080" in the hole, and 67 cc chambers I come up with 7.44 to 1 compression. Make the chambers 72 cc's (the smallest stock 340/360 chambers I've ever measured) it drops to 7.13 to 1. I have never measured 318 head chambers so I'm taking Justin's word for it that they are about 67 cc's.

True it only drops the compression .3 using those figures. But I think your in error with your calculations.