Compression Ratio Calculations/Dimensions
This information was taken from the mailing list. It was posted by Jim Beeler. Note the effects upon compression ratio by using different head gaskets, milling decks, heads, etc.
Been awhile so guess I'll post this again for the newer members. Been
running one steel shim @ 9.31 cr with Caterpillar bolts since '91.
"Lifted" the head once, these steels don't "blow" out, just loose
sealing ability and make a neat whistling sound.
V6 Cylinder Head and Gasket Combinations
Stock cylinder head cc=48cc
" " " milled.025"-.030" cc=43cc
Stock head gasket (.060" compressed) cc=11.15cc
P/N 1000 Fel Pro (.0375" compressed) cc= 7.8cc
P/N 1007 Fel Pro (for "o ringed" heads)
(.039" compressed) cc= 8.6cc
Two steel shim .018" (.036") cc= 6.9cc
One steel shim .018" cc= 3.45cc
Piston deck height (.030") cc= 5.57cc
Piston dome(+cc)/dish(-cc) cc=-24cc
Formula:
c-p+g+d+v
cr (compression ratio) = _________
c-p+g+d
c= head volume (stock 48cc)
p= piston dome/volume (-24cc)
g= gasket volume (11.15cc)
v= cyl volume (b/2)2 X s X 51.48 = (bore/2)2 = 3.8"/2= (1.9)2
=3.61 X s (stroke 3.4") = 12.274 X 51.48 = 631.87 swept volume
d= deck height (5.57cc)
Sample 48-(-24)+11.15+5.57+631.87 =720.59
cr= ________________________ ______ = 8.122 cr
48-(-24)+11.15+5.57 = 88.72
Substituting values we get:
Head milled .025-.030" (43cc) w/stock .060" = 8.55 cr
" " " " " 1000 Fel Pro .0375" = 8.86 cr
" " " " " 2 steel shim .036" = 8.95 cr
" " " " " 1 steel shim .018" = 9.31 cr
Stock (48cc) with stock gasket .060" = 8.122cr
Stock " with P/N 1000 Fel Pro .0375" = 8.40 cr
Stock " with 2 steel shim .036" = 8.48 cr
Stock " with 1 steel shim .018" = 8.79 cr
As stated by Lawrence Conley at the Turbo Tech sessions in 93 and
94, "there are no downsides to increased compression." Some of
the engines being built by them are running 10.1 ratios. They
will require "good" gas as boost levels increase above 15 lbs.
Jim Beeler, jbeeler@ telepath.com
GSCA 3526, 11.51 @ 119.63mph