I am woundering what would be the compression change if swaping a -16 cc with -7cc dish pistons, assuming everything remains the same; head, cam and so on.

I have estimated 1.4 points increase in compression. Someone correct me if I am wrong.

I will be using stock LT1 pistons in a Jeep I6 4.0L engine, will be 0.125 over bore size in that engine and want to know my new compression. The stock pistons cc of the 4.0L engine is -16.

 

1.3-1.4 drop in compression...but it varies depending on bore/stroke, gasket thickness...etc...

 

You mean increase not drop.

Great, that would put me at 10.2-10.4 compression with the LT1 pistons. Kind of high but it will work on 93 Octane gas.

 

Yeah...I thought you were going from a 7 to 16 cc dish for some reason

 

The 4.0 has an Iron head right? I'd take a little more detonation precautions as well.

 

10.2-10.4 should be fine with 93 and an iron head, I was running 10.7 in the K5 Blazer with dart iron eagles

 

Combustion chamber efficency helped that out alot.

 

Yes, it is. Mine is also stroked using 4.2L crank and 4.2L rods. So, it will be 4.8L with 0.125 overbore using LT1 pistons. It will be around 280HP 6-cylinder engine. Was running it for more than a year using 0.040 oversized Jeep pistons. Now I am rebuilding it cause I had a broken valve and piston.