Uh, you clearly stated that a compression ring makes little difference
as relates to oil control. In fact, any broken compression ring will
substantially affect oil control.
Additionally, broken oil or 2nd compression rings are rare since the
malady is often caused by incorrect timing (or some other direct factor)
that leads to detonation which is the chief culprit as to ring breakage.
I have a question for you. I was taught that the best method of detecting
ring problems was to conduct a compression check. Other than taking the
engine apart, are there now better methods of detecting ring problems? If
so, what are so methods?
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for general engine health, i.e. how well it's coping with accumulated
mileage, that's true. but in the situation cited originally in this
thread, it's not guaranteed to diagnose the problem because defective
oil control rings make almost no difference to compression. you're
therefore left with logical deduction - if all other causes have been
eliminated, it's the rings.
oil/excess deposits on one spark plug is a dead giveaway. in addition,
oil analysis could do it, if conducted regularly. but in a situation
where the engine's suddenly dry, analysis is not an option. that
unfortunately leaves you with strip-down. but even then, there's not
too much point messing about worrying what went wrong - once stripped, a
motor needs to be rebuilt anyway and all the wearing parts need to be
replaced, so just toss the pistons and rings and start again.
That agrees fairly well with my limited experience. I rebuilt an engine in a
1970 Volvo I had that pinged badly and smoked a lot (no catalytic
converter). It had broken first compression rings in every cylinder and a
broken second compression ring in one cylinder.
Back in the early 1980's, I bought a friend's 1976 Honda Civic CVCC and
drove it for about a year. It pinged fairly loud on hills and hard
acceleration but luck was with me as I finally adjusted the timing to
get rid of the knock. The car ran flawlessly all the way to the 170K
(miles) mark when the car rotted out from under me...
(Who wonders what adventures may lurk with his "new to me" '83 Civic FE)
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