compresion test results are they good or bad

[302mustanglx]

Okay guys like the titlle says i did a compresion test on the car beacause i found oil or gas on the treads the results were.


cylinder1 60
cylinder2 60
cylinder3 70
cylinder4 70
cylinder5 60
cylinder6 70
cylinder7 70
cylinder8 75

now the car runs great no overheating oil presure looks good just when i get on it smokes a bit or when i rev it. smoke color looks gray bluish what do these num mean are they to low do i need to rebuild your help is apreciated

 

[CarMichael Angelo]

Those numbers are pitiful. If you are performing the test like you're supposed to ( w/ the TB blocked wide open), you trust the compression tester as accurate, and you're only getting 60 lbs per cylinder, I think you're down about 50%- 75% . Smoking under acceleration is a sign of worn rings. It's one thing to follow a car that smokes because it's pretty easy to see and smell. It's harder to see it from the mirror though. If you can see the smoke in your rear view mirror, your engine is pretty tired. Smoking at idle or deceleration is a sign of worn guides or bad seals.

 

[txstang84]

Wow-yeah, 60-70 psi is pretty low...looks like a great time for a new engine


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[302mustanglx]

It only does it when it gets rev up or when i get on it. This moter i have on know does not have more then 5000 miles on i dont get why it would be doint that all bearings piston rings got replace what do u mean by w/ the TB block wide open.

 

[CarMichael Angelo]

It only does it when it gets rev up or when i get on it. This moter i have on know does not have more then 5000 miles on i dont get why it would be doint that all bearings piston rings got replace what do u mean by w/ the TB block wide open.

Still not using the spell check thingy eh?

Who put the rings and bearings in? Just because they're new, doesn't mean it was done right. The fact that you have such weak compression, and a smoking engine reinforces that there is something bad wrong. W/ new rings, one cylinder low would mean that there was a broken ring, or it was the wrong part, or just incorrectly installed. EIGHT low cylinders means that you definitely got something wrong across the board.

I mean open the Throttle Body, and block it that way so the engine can get as much air as possible when you perform the comp test.

 

[VibrantRedGT]

Also I use a battery charger on the battery during the compression test. Keep the throttle body open like Mike said plus use a battery charger and I bet the results are better. Although you probably need to be around 100-125psi (mine pulled 132psi in all 8) and you're pulling half that which isn't very good. Sure does sound like a ring issue.

 

[FastDriver]

Those numbers are pretty good since you didn't have the TB blocked open. Try it again.

 

[jrichker]

Pull the inlet duct off the throttle body and stick the plastic handle of a screwdriver in between the throttle butterfly and the throttle body walls. That will prop the throttle open and the soft plastic will not damage anything. As suggested, use a battery charger when doing the test: if the engine cranking speed is low your results will be inaccurate.

If you really want to know what the problem is, use a blow down compression tester that puts air pressure inside the cylinder. You'll need a good air compressor with at least a 15 gallon tank to do the job. See http://bellsouthpwp.net/l/r/lrichke...ession_tester/Blow_down_comprssion_tester.htm for a how to build your own tester and use it correctly.

Free spell checker for your computer - download at www.iespell.com/download.php

 

[bentley429isBAC]

I am thinking he just tested it incorrectly. If it was that low across id have a hard time believing it was tunning great, seeing as it probably wouldn't run at all.

 

[CarMichael Angelo]

I am thinking he just tested it incorrectly. If it was that low across id have a hard time believing it was tunning great, seeing as it probably wouldn't run at all.

Oh I agree, I think he needs to retest again too. Regardless though, it's not running that great. He said it smokes. I'll bet he picks up 10% when he blocks the TB open.
Any takers?
Maybe we could start a gambling subforum, and be the first Mustang website to give odds (and pay dividends) on whose thoughts are closest.
Or at the very least, keep some sort of record of who offered the most accurate,..inaccurate, or full on BS solution to a problem.

 

[CarMichael Angelo]

Actually,...That isn't such a great idea after all. One individual would clean up.

jrichker would become the sites richest man here as a result of continuously offering the MOST informative, technically accurate solution to a problem.

It'd be like going to the track thinking you got a chance at winning today and finding out that Tommy Twin Turbo is there too.