360 more static = ? problems

[360moparjunkie]

Darrell

Current piston to deck is .1092 average
Using the helpful comp cam static comp. calc. (thank you fabo member) I currently have 8.397 static comp.

This is w/ new flat top pistons (not dished). These pistons DO NOT have valve reliefs.

Providing we shave the deck .080" this will increase static to 9.861, what I think (open to sugg.) is a good target compr. number.

What risks of valve to piston interference will I create if the block is decked .080"?

What is the best way confirm this is not an issue. (Mock up valve train w/ 2 solid lifters and rotate valve train by hand?) I am not sure and I want to be.

The factory '72 "J" heads were shaved years ago (cc confirmed @ 67cc)
34189c / AAWWJ360

Thank you members for all the great help so far.

 

[moper]

If it were me I would cut the heads a ton before I cut the block. It's easier alter to dump the top end and replace things than cutting the block. You can whack .100" off the heads, knocking the volume down a solid 10ccs at least. (total reduction depends on the chambers your heads have now...) Now, cutting heads to avoid changing pistons causes it's own issues. I'm listing what they are, and how much it would cost me to address them: 1. Head bolt lenght may be too long. Free fix.. make sure the threads are tapped to the bottom of the holes and/or perhaps shorten the bolts by the same .100". Just make sure the threads are in very good shape after as that will affect torque value when tightening them. 2. Pushrod length will effectively lengthened. New custom length pushrods $120. 3. intake fitment. The heads can't be cut that far on the intake mating surface. So you have to cut the intake itself to fit. Head gasket surface milling (extra passes due to amount removed) $150. Intake surface milling (includes ends) $150. 4. Pushrod clearance to head - not all heads will have this but earlier ones might so check it- free fix. Grind psuhrod hole to clear. 5. accessory bolt holes in heads will have moved closer to deck surface so you may need to enlarge bracket holes to get things to attach properly. - free fix. File/grind holes larger. Total for big milling for compression = $420.00 beyond std work and the heads and intake are forever matched. By doing that you will gain a little more than one full point of static compression. But remember you are starting from 7.5... so it doesnt help too much if you're looking for 9.5:1. It will cost a little more to swap pistons. But if you are dead set on getting more out of it I'd still do that instead.