Bob----It is accepted by most sources that "even" compression across all
cylinders is better than variations that exceed 10%. Given that the
stock head thickness for a '75 is 3.580 and comparing it to other
thicknesses and CR's, a head such as yours should read closer to 125 lb.
My '73 head that now measures 3.540 (after being cleaned up a couple of
times) comes in at the 145lb. that you are seeing.
It has been written in several reliable sources that it is possible to
raise the compression pressure (not ratio) by advancing the cam shaft. I
have not personally tested this, but could this be one of the reasons
for your higher-than-
normal readings?
Dick T.
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