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Old 05-17-2011, 05:22 PM   #1
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Default Opinions on compression test numbers, please.

I'm planning to go with a Rotrex kit down the road. I might even be upgrading it a bit (200 - 220 whp). So, I did a compression test (thanks for the help, Kuksi).

Front to back:
#1: 203 psi
#2: 199 psi
#3: 182 psi, 188 psi after a bit of oil
#4: 199 psi

We were a little short on time, so we only re-tested #3 with oil since it was a bit low. From what I understand, these figures are still within factory specs but what are your thoughts on that 3rd cylinder? Is it a problem and if so, what is likely the issue? If I decide to fix it, what else should I consider doing at the same time?

- Tom
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Old 05-17-2011, 05:33 PM   #2
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There can be up to 28psi difference between cylinders within spec.
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Old 05-17-2011, 05:39 PM   #3
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Its not horrible but its not good either. if you're going to go in there id freshen all gaskets/seals/bearings and possibly throw in some forged rods
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Old 05-17-2011, 06:01 PM   #4
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Do a leakdown on #3. I betcha it's a leaky exhaust valve.

If while applying pressure into #3 with it at TDC, and you listen to the other cylinders' spark plug holes with a hose, and you hear the hissing in #2 and #4 and not #1, it's the exhaust valve. If you hear it in #1 and #2, it's the intake valve.

It's loudest in the oil filler cap, it's the rings.
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