Stupid question, but I'm curious if one could infer healthy compression in the cylinders from an idle vacuum reading or 20"?
Possible to have 20" of vacuum AND low compression?
- Thread starter Dustybottoms
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I would just test the compression wet and dry. That is good vacuum pressure, how good is your gauge?
- Thread starter
- #3
Oh I intend to test actual compression, was just curious. For the vacuum test I used both a hobo-freight gauge and a snap on. Surprisingly, the hobo-freight read the same as the snap on.
Is it a steady needle at 20" of vacuum? What happens if you goose it WOT? Low compression may or may not affect the vac readings.
Worn rings might be able to pull a good vacuum but not be able to hold the 5 times pressure 20" vs 120psi.
Would like to add do it cold and hot (op. temp.) and see how much difference.
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- #7
Didn't think of it this way. Hmm
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- #8
The engine was at operating temp, fyi. Didn't measure it cold.
I favor a leak down test along with a compression test, it can tell you a lot about the condition of the engine.