Compression Test Q & A...
06-28-2004, 01:05 PM
#1
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Join Date: Mar 2002
Location: Vicenza, Italy
Posts: 279
Compression Test Q & A...
As you all know, I'm taking a friend of mine to go look at a Camaro (85') and I need to know what psi is acceptable (at the minimum) in order for the test results to be definitive. This is kinda urgent if anyone's on right now. Also, he wants to check out an 86' Trans AM, I'm assuming the numbers should be the same correct?
As far as the test itself is concerned, I'm pretty sure how to do it but not positive. Its been a while since my auto tech days. Basically, I need to have the battery close to fully charged.
Next, I need to disable the fuel system. If its 85' I'm assuming its carbeurated, so how do I keep the carb from spewing fuel?
Unscrew one spark plug at a time, screw in the vacuum gauge, and crank the engine repeatedly for around 10-15 seconds.
As far as the test itself is concerned, I'm pretty sure how to do it but not positive. Its been a while since my auto tech days. Basically, I need to have the battery close to fully charged.
Next, I need to disable the fuel system. If its 85' I'm assuming its carbeurated, so how do I keep the carb from spewing fuel?
Unscrew one spark plug at a time, screw in the vacuum gauge, and crank the engine repeatedly for around 10-15 seconds.
Last edited by Trans AM 22502; 06-28-2004 at 01:14 PM.
06-28-2004, 07:32 PM
#5
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Join Date: Jun 2003
Posts: 252
yes, 4 or 5 rev's for each
the correct way would be to take all the plugs out and block the throttle wide open but you can do it with the other plugs in if you need to (thats how running compression test is done)
write them down
should be within 20% of each other
if some are low you can do a wet test to see if its the rings or valves by squirting some oil into the cylindar (if you plan to do that then post and we can elaborate)
type in compression test on google and im sure you can get a whole step by step procedure ive seen tons of them on thoise do-it-yourselfer type sites
oh and disconect the primary wires from the distributor so that the engine does not start (colors? hopefully someone else can chime in)
the correct way would be to take all the plugs out and block the throttle wide open but you can do it with the other plugs in if you need to (thats how running compression test is done)
write them down
should be within 20% of each other
if some are low you can do a wet test to see if its the rings or valves by squirting some oil into the cylindar (if you plan to do that then post and we can elaborate)
type in compression test on google and im sure you can get a whole step by step procedure ive seen tons of them on thoise do-it-yourselfer type sites
oh and disconect the primary wires from the distributor so that the engine does not start (colors? hopefully someone else can chime in)
06-29-2004, 01:23 PM
#6
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Join Date: Mar 2001
Posts: 3,249
I take all plugs out and keep it at WOT. I would crank it till the gauge needle stops moving up. If the cylinders are not within 10% of each other, I run like hell. If they are, I squirt oil in all the cylinders and rerun the test. If they cylinders show a marked increase from the first run, I also run. That means that the rings are not sealing like they should.
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