I know that for a compression test, you're supposed to
make sure that the cylinders are within a 10%
differential of one another, to determine if one or
more cylinders is wearing worse than the others. But
if they're wearing equally, and your compression is
staying steady between cylinders, you don't really
know when it's time for work on the engine.
No one ever says a particular number is bad or is a
good compression for the cylinders. Checking my spits
compression, I have 139 psi (a hair under the 140
mark) on all of my '77 cylinders, but I seem to
remember my last engine having compression of around
170 psi on atleast a few of the cylinders (this was on
a flat top '76 engine.)
While watching Shadetree mechanic a few weekends ago,
they were testing the compression on a late 60's
corvette and it had readings in the 145 lb. area. and
they said it was "worn" and probably due for new
rings.
What's a "Good" reading for a spitfire?
-Terry
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