Timberwolf

iTrader: (8)

I know it is listed in one of my books, but I can't find it. Any help here?

Taspeed

iTrader: (1)

i'm coming up with 11.34:1 with .045 head gaskets and assuming you are using a flat top piston. also with the piston out of the hole about 11 thou.

i'm not sure what the piston out of the hole is, but I think it varies a little from motor to motor. Hope this helps.

edit: using the same formula with .050 gaskets and .007 piston out of the hole your looking at 11.23:1

Here is what I used:

CR = (SV + CV) / CV

where:

CR = compression ratio
SV = Swept Volume (displacement of one cylinder)
CV = Compressed Volume (volume at piston TDC)

To get the swept volume of one cylinder in CCs, the handy formula is:

bore x bore x stroke x 12.8704

For a stock short block, this works out:

3.90 x 3.90 x 3.62 x 12.8704 = 709 CC (rounded up)

Compressed volume is the sum of chamber volume, deck volume, gasket volume, and piston dish volume (including valve reliefs). For a stock LS1:

Chamber volume = 66.67
Deck volume = 3.9 x 3.9 x 12.8704 x (-.006) = -1.17 CC (negative because piston out of hole)

Gasket volume = 3.9 x 3.9 x 12.8704 x .060 = 11.7 CC (guessing on the gasket bore?)

Piston dish volume = 0 (true flat top piston)

Thus CV = 66.67 + 11.7 - 1.17 = 77.2 CC

Put all of this into the first formula:

CR = (709 + 77.2) / 77.2 = 10.18