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Analyze my compression test please... #473561
09/20/09 05:02 PM
09/20/09 05:02 PM
Joined: Jan 2003
Posts: 1,046
Colorado Springs
T/A CARe Offline OP
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Just did a static compression check. All cylinders had 125 psi (and leaked pressure somewhat quickly after stopping the engine turnover). Had a couple dark, oily plugs (uh-oh...) that went to 130 and held pressure.

Thoughts?

Re: Analyze my compression test please... [Re: T/A CARe] #473562
09/20/09 05:37 PM
09/20/09 05:37 PM
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Rancho Cucamonga, CA
D_C Offline
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Usually, compression testers have a check-valve that doesn't allow pressure to leak back into the cylinders.

Does your tester not have a check-valve or did you remove it?

Also, even "good" cylinders leak down after a relatively short time.

That said, if the compression is Ok according to engine specifications and within around 10% cylinder-to-cylinder, highest to lowest, your rings "may" be Ok.

A test is squirting some oil in the cylinder and retesting to see if there is an appreciable rise in PSI.

The oil-burning "may" instead be as result of valve-seals, worn valve-guides, leaking intake-manifold gasket, etc

I had similar results on an engine I tested a couple months back. Though the engine had had a complete valve job with new seals around 8-months earlier, I replaced the valve-seals and that stopped the oil burning.

Another Moparts member recently had an intake manifold, leaking oil from the underside into the cylinders.

Re: Analyze my compression test please... [Re: T/A CARe] #473563
09/21/09 09:47 AM
09/21/09 09:47 AM

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what motor did you do the test on? i got a 73 valiant all stock with a 318, 80,000 miles on it and did a comp. test in my auto tech class and i had an average of 145 psi.

Re: Analyze my compression test please... [Re: D_C] #473564
09/21/09 12:55 PM
09/21/09 12:55 PM
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Posts: 21,318
Manitoba, Canada
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Check your compression tester, it should have a check valve in it so the gauge stays at the highest reading until you release the pressure manually. I found when I tried my comp tester it was leaking down so I had to redo the gauge connection on it with teflon tape. Now the reading doesn't leak down anymore and the cylinders read 10psi higher.

Re: Analyze my compression test please... #473565
09/21/09 03:11 PM
09/21/09 03:11 PM
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Pikes Peak Country
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Quote:

what motor did you do the test on? i got a 73 valiant all stock with a 318, 80,000 miles on it and did a comp. test in my auto tech class and i had an average of 145 psi.




TA Care's altitude of 6000 ft puts a 120psi cranking pressure the equivilent of 150 psi at sea level, with certain engine assumptions, but, you get the jist of the difference.

The cylinders that had 130 and held pressure tells me there is a valve in the guage to hold pressure, otherwise all the cylinders would have quickly leaked down. So there may be some other issue.

Re: Analyze my compression test please... [Re: T/A CARe] #473566
09/21/09 04:10 PM
09/21/09 04:10 PM
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Upper Midwest
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You do realize that you can have good compression and still have oil usage, don't you. Imo there is nothing really wrong with the compression of your engine. Sounds to me like tehr is something wrong with your tester to leak down.

Re: Analyze my compression test please... [Re: T/A CARe] #473567
09/21/09 04:32 PM
09/21/09 04:32 PM
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USA
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After checking the threaded connections on your gauge,
you might consider doing a
"Dynamic Compression Test"
which has the potential to more accurately 'zero in' on what might be wrong:

http://www.misterfixit.com/dyncompr.htm

Re: Analyze my compression test please... [Re: 360view] #473568
09/21/09 11:19 PM
09/21/09 11:19 PM
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Posts: 1,046
Colorado Springs
T/A CARe Offline OP
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The first cylinder I tested, was the 130 psi and the gauge held it until I released it with the needle valve (tire valve) release. So I think you all may be right that I have a gauge issue.

Thanks for the clarification on the altitude too Tony. I was curious what that might be.

Is there a way to tell where the oil may be coming from (without pulling pieces)? I'm not opposed to pulling things, but if there's an easier check...
Thanks again!

Re: Analyze my compression test please... [Re: T/A CARe] #473569
09/22/09 07:21 AM
09/22/09 07:21 AM
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USA
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http://www.amazon.com/Milwaukee-2300-20-M-Spector-Digital-Inspection/dp/B001AOVBHG

notice how the price has come down

on inspecting for the source of oil
you would snake into the valve cover looking at intake valve stem seals that might have pop'ed up,
and then snake into the combustion chambers looking upward at intake valves in both the closed and partially open positions by carefully turning the crankshaft ... but don't let the piston crush the camera !

Re: Analyze my compression test please... [Re: T/A CARe] #473570
09/22/09 08:30 AM
09/22/09 08:30 AM
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Upper Midwest
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does it smoke when started after sitting a while?? This is a good sign of guide wer ot valve stem seal failure.

Re: Analyze my compression test please... [Re: MoparforLife] #473571
09/22/09 11:36 AM
09/22/09 11:36 AM
Joined: Jan 2003
Posts: 1,046
Colorado Springs
T/A CARe Offline OP
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No smoke when I start it.

I have noticed a little blue fog in the mirrow at high rpm shift points.

And sorry, haven't had the chance to check the exhaust pipes for oil residue (yeah, I know it's easy, I just keep forgetting... that and bending over these days is asking a lot! ) I have an H pipe so won't be easy to tell which side might have a problem...

Re: Analyze my compression test please... [Re: T/A CARe] #473572
09/22/09 11:47 AM
09/22/09 11:47 AM
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Columbia, CT
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If the plugs are oily, you know it's getting in the engine and burning it. If you decide to fix it, pull the intake and see if it's coming down the intake valves as it will be easilly visible. If the ports are all wet with oil and fuel, you will need to work on the tune after the work. If it smokes at rpms, it's ring seal.. Or more precisely oil control ring issues and it won't go away until you get deep into it. The compression figures are ok for your altitude but oil drops octane dramatically so you may have ping or detonation issues too.


Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.






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