I am wondering everyone seems to agree that for real power give my 390 10 or 10.5 to one CR then a good size cam to bleed off sme cylinder pressure. And have .012 deck height. But trwlz291f pistons won't even reach 10 to 1, I can't find a piston to meet all these criteria. These pistons plus my c8ae-h heads 71 cc will only be about 9.2 to 1.
Any ideas??

 

I'm building a 390 with the TRWs for my 76 F150. Heck, I'm just happy to have more compression than the 7-something- to- one in my current 360!

 

According to my calculations, those pistons (TRW-L2291) with 71cc chamber volume, .030" overbore, and Fel-Pro head gaskets, give you 9.6:1 compression. If you use .020" steel shim head gaskets, you get about 10.2:1.

Recheck your calculations.

 

What about deck height it's kinda important to be around that .012 instead of .031 or so isn't it?

 

Well Deck height and chambers size and gasket thickness..

RJ

 

TRW L2291's have a 1.776" compression height.

Stock FE deck height = 10.17"
390 crank throw = 1.892"
390 rod length = 6.488"

Doing some simple math:
10.17-1.892-6.488-1.776=.014" deck clearance

When I put my 390 together with TRW L2291's, it had a deck clearance of .012". Close enough to the calculation.

Most Fel-Pro head gaskets have a compressed thickness of .041" and a diameter of 4.4". Look up the specs on your desired gaskets to get more accuracy there.

Now go here and plug in your numbers:
http://www.kb-silvolite.com/calc.php?action=comp