
Compression
Ratios
Here is some
information that might be of interest to
people. Thanks to Larry Young of
Tulsa, Oklahoma for this. Larry cc'd
various heads. These are the results he
got. The total volume of the cylinder is
44.2 cubic inches. The total volume of
the part of the piston that sticks up
above the bore is 2.86 cubic inches. The
head gasket holds .92 cubic inches. The
total combustion chamber is the head
volume minus the volume of the part of
the piston that sticks above the bore,
plus the volume of the head gasket. Using
the stock head as an example: 17.9 minus
2.86 plus .92 = 15.96 cubic inches for
the total volume of the combustion
chamber. Cylinder volume plus combustion
chamber volume divided by combustion
chamber volume equals the compression
ratio. (44.2 + 15.96)/15.96 = 3.77:1
The first number will be the head volume,
the second will be the calculated
compression ratio.
Stock head 17.9 = 3.77
Stock (milled 1/8") 15.6 = 4.24
WaukeshaRicardo 16.6 = 4.02
Zhead 13.7 = 4.76
Zhead (milled .050") 12.8 = 5.07
Reeder 12.2 = 5.31
Now the same figures for an engine bored
.060" over.
Stock head 3.86
Stock (milled 1/8") 4.34
WaukeshaRicardo 4.11
Zhead 4.88
Zhead (milled .050") 5.2
Reeder 5.44

