hankfan79

I have used 2 different calculators and come up with 1.38 which has to be total BS!

Here is what I know:

9.240 Deck Height
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke

What am I missing?

98CayenneT/A

Where you have 9.24 for deck height, they want to know how far out the hole the piston is.

Like on my Ls1 it is .007"

98CayenneT/A

If you are running flat top pistons and I put your info in with a deck height of .007" I get 10:1 CR

98CayenneT/A

Just saw your 4cc pistons and I put your info in again and got 9.6 : 1 CR

hankfan79

Well damn. I am trying to get to at least 11:1 without a head swap.

98CayenneT/A

Have your heads milled down

Mill the heads down .060" and run a .040" head gasket should get ya there

JimMueller

iTrader: (9)

9.240 Deck Height > I used -0.007 instead
6.125 Rod
73cc head
-4cc Piston
4.030 Bore
.051 Gasket
3.662 stroke > Is this a typo'ed 3.622 or is it really 3.662?
Gasket bore? I'll guess 4.040

With the assumptions above, I get 9.778 static compression. Milling the heads to 63cc (~0.055") will net you about 11.1:1. I'd leave the gasket at .051 since that'll put your quench around .044. You can get a thinner gasket but then you'll be on the bleeding edge of safe quench.

LS1MCSS

iTrader: (18)

Stroke should be 3.622

hankfan79

Yes it was a typo. Thank you.
Would milling that much cause me to have intake fitment issues?

They are mahle flat tops with valve reliefs. -4cc
I believe by the time I pay to mill these heads, it might be cheaper to pick up a set a used 243's.

Thanks for the input guys.

98CayenneT/A

I would say you would probably have intake seating issue.
Could have the intake shaved also.

Or just go with the 243's.
Have them milled .020" - .030" and run a .040" head gasket and you will be around 11:1 CR and not have to worry about intake fitment.