Hi, Shane---As you know, a compression test measures pressure, and while
it's related to the compression ratio, the two are different. It's
possible to have a high CR and not have high pressure. A lot depends on
the type of cam shaft used and to some degree, how the cam is timed. In
any case, a compression test measures the air trapped between the piston
top and the combustion chamber. Under most circumstances, a low
compressioned head will give back lower pressure readings. I just
measured fellow owner J. Lopez' 1974, recently overhauled engine. Stock
head at 3.580. It showed 120 lb. with a performance cam. After
installing a stock cam, (long story) the pressure rose to 125 lb,
indicating the performance cam bled off some of the pressure before both
valves closed.
In short, I don't think there are many stock '74's that have a CR as
high as yours. It would be interesting for others with the late (stock)
head to give feed back on this.
Listers?
Dick Taylor
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