Re: Toms compression test

[Tom Harais <tjhemh@domain.elided>]

John:

I just happened to remember that compression listing as one of the IH
unique characteristics. These engines are not finicky and have very wide
tolerances. I've noticed that in everything I've read, including the 75%
between highest/lowest cylinder compression as being acceptable.

I was trying to tell someone the other day, that this was why the IHs
and many of the 60s and 70s cars have so many idiosyncrasies. They have
large tolerances and they will go forever, especially the IH, compared
to high tech, aluminum block, OHC, fuel injected modern engines. The
modern ones have very tight tolerances and are much better efficiency,
top HP for same displacement and overall running wise. But, those much
tighter tolerances make them somewhat finicky and more susceptible to
minor disturbances creating major problems.

The ease of stripping the plug threads on an aluminum head and the
problems of repairing that compared to how hard it is to strip the plug
threads on an IH and how a simple helicoil would fix it is one example.

The potential for warping or destroying an aluminum head on virtually
any econobox these days from overheating it compared to how many times
you can overheat your IH and not cause significant damage would be
another.

And, it isn't that one is better than the other; it is a difference in
design parameters due to the priorities of the times that each was
designed in.

Tom H.