In a message dated 8/18/2005 10:08:09 AM Central Standard Time,
tswrace@pacbell.net writes:
> I put a cam in my Ford 30 yrs ago. When I rebuilt it I spoke to the cam
> manufacturer. The original caqm card said .014 lash. The manufacturer
> said to change to .018. It apparently makes little or no difference in
> the compresion. It does change the torque curve.
>
What? Are you saying that cam timing has little or no effect on the
compression test gauge? Or that valve lash has little or no effect on the
gauge
reading?
>From what I've been hearing the absolute numbers are not as important as the
variation from cylinder to cylinder and a low reading could be from faulty
rings or valves (or something more catastrophic like a hole in the piston but
that has other symptoms). Furthermore, if there is a significant difference
between the dry test and the test after a little bit of oil is injected it is
likely the rings. No real change and it is likely valves.
But if you run the dry test and the wet test and you have a low cylinder,
check your valve lash. It just might be because a valve is not closing (which
could be valve seat recession -- but that is something that can be ignored for
a
while) and you just saved yourself a head R/R.
Better yet, set or at least check the lash beforehand.
Dave
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