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I’m pulled all my plugs and the injector fuses and going to do a compression test on Stock LS6 51,000 miles What should I hope to see on a heathy engine
Why I asked is your profile says 08 base ??…best to edit your profile if incorrect…didn’t know if I needed to move you over to C6 Tech…either way FSM says 100 psi minimum but they are more concerned with the variance between the highest and lowest reading cylinders !!…maybe someone with actual numbers if that is what you need may chime in but 200-210 would be about right…Service Info in Alldata and Mitchell say the same thing about 100 psi minimum and variance…I normally do a running compression test vs static with a scope and pressure transducer for seeing how much air the engine can “breathe” !!
That 100 psi is relative to the 4 compression strokes. Many a generic description indicates spinning the engine to peak the measured compression — counting 4 puffs and stopping will be much more accurate.
I haven’t taken the time yet to figure out how to change my profile since I replaced 08 with a 22 Z51. The Zo 6 belongs to my Brother and I am helping do some miscellaneous repairs on it . Anyway thanks for the info on compression . I’m expecting to get my test gauge today and will revisit this tread with results. There seems to be quite a variance in readings I should see , is it 100 psi minimum and 70% variance Or 200 to 210 as you stated ?
The only thing I don’t like about a static compression test is that it will sometimes not reveal a mechanical issue since the cylinder pressure is trapped in the gauge…a cranking compression with a pressure transducer over 15 seconds will reveal an issue possibly not seen by just cranking the engine 4 or 5 times.
I haven’t taken the time yet to figure out how to change my profile since I replaced 08 with a 22 Z51. The Zo 6 belongs to my Brother and I am helping do some miscellaneous repairs on it . Anyway thanks for the info on compression . I’m expecting to get my test gauge today and will revisit this tread with results. There seems to be quite a variance in readings I should see , is it 100 psi minimum and 70% variance Or 200 to 210 as you stated ?
You will probably see 200 or so but I read it as 100 psi minimum…some of the Tech writers and Engineers at GM weren’t the brightest…you can see where you can edit your profile…upper right and click on the down arrow next to your username…the more info the better if you need help with something…why are you needing to do a compression test ??…just needing a baseline reading ??…as far as taking the reading yes you can pull the 2 injector fuses but the throttle blade should be wide open…and with these electronic throttle bodies just keep your foot to the floor on the gas pedal when cranking…known as a “clear flood crank” !!
Not to sidetrack the thread, but how do you get a transducer in system? I've got an appropriate DC transducer and a 4 channel data logger that I've been going to use for a recorded compression test, but that would just be an alternate method of spark plug substitution.
I just did my compression test range was from 190 to 210 New plugs and wires the reason I checked compression cause the engine has a vibration 1500 to 3500 does it in neutral and in gear I wanted to be sure engine was healthy , pulls and seems to smooth out at around 4000 and up was noticing people talking a lot about the harmonic dampeners going bad , sure enough I noticed it was wobbling and some of the rubber looked dried up and distorted , Could this be the source of my engine vibration ?
Compression testing
