Compression and milling on 4.0 head

What are anyones thoughts on milling .010-.020 off a 4.0 head for a bumb in compression when I rework my head and a valve job/ gasket match. Its a renix 4.0 I dont want to swap to the HO setup just a little more pep. I have built a sick 225 slant 6 head and I cut over .120 on that motor to raise my compression but I have no experiance with the 4.0s. What is the stock compression anyway.

There is a thin high performance head gasket from MOPAR that will give you more compression without having to mill the head.

When I had my 90 RENIX rebuilt, the machine shop milled the head and decked the block for a total of .030. They also bored it out to .040 due to #3&4 pistons being melted completely down after a 30 mile drive with no coolant and a blown head gasket and scoring the bore's (these are tough engines!)

I can tell you it runs awesome! I have 5 XJ's, one RENIX and 4 HO's and the RENIX will run step for step with the HO!

You should be fine with that amount of milling. I have not done this but it seems you might get a little ping under hard acceleration after the head is milled.

Stock compression is low, around 8.7 I think. Using my calculator decking the head .020" and using the mopar .043 (I think) head gasket should yeild around 9.2 CR. Running premium will help against ping.

My last head got milled .040 and was fine.