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Compression check?

This is a discussion on Compression check? within the Internal Engine forums, part of the LSx Technical Help Section category; Just like the title says, ive been lookin through forums trying to find a post and can not find one. ...

  1. #1
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    red
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    Compression check?

    Just like the title says, ive been lookin through forums trying to find a post and can not find one. My car was miss shifted 2-3-2 and over revved. Bent 7 pushrods which i have replaced already but im afraid of wether or not a valve has been bent. So i was wondering just exactly how and what is the easiest way to do a compression check. Also if im in the wrong forum or this another post about this please point me in that direction. Thanks for any help

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    red
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    Does ne one know how exactly this works. What I believe i need to do is get a guage pull out each plug and put the guage in its place one by one, fire it up and write down the compression for each cylinder? Obviously if theres low compression in one then a valve is most likely messed up. I just want to make sure im doing everything proper and where can i find a guauge already set up for this? and what should the compression be?

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    Simpsons Did it!! 98formy's Avatar
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    take each plug out and screw in the adapter piece from the gauge. Turn it over and see what it reads. I dont know what the compression should be, but when you do all eight cylinders, just see how consistant they are. If you have a bent valve, it will read very low or at zero for that particular one.

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    Your engine is not going to crank up and start, you just want to spin it over about 5 seconds. Before you start checking the compression, Take all the spark plugs out of the engine. Then start at 1 cylinder and make your way to the 8th one. Whenever I do this check I pull out the fuel pump fuse to keep the pump from running. Keep an eye on your voltmeter gauge, don't let the voltage get to low or your starter may not turn as fast thus affecting your readings. LS1's have a 10 to 1 compression ratio, I have no idea what that equals to in PSI. I have done this check on 5 vehicles and not one of those was an LS1. I'm going to guess and say around 195 to 200 psi. Good Luck with it.

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    Impounded
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    Quote Originally Posted by miller456 View Post
    Just like the title says, ive been lookin through forums trying to find a post and can not find one. My car was miss shifted 2-3-2 and over revved. Bent 7 pushrods which i have replaced already but im afraid of wether or not a valve has been bent. So i was wondering just exactly how and what is the easiest way to do a compression check. Also if im in the wrong forum or this another post about this please point me in that direction. Thanks for any help
    Stock push rods? or aftermarket?If it was the stockers just replace um and its probably ok.If it was aftermarket push ods your valves are bent.

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    Senior Member mrr23's Avatar
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    unplug the coil packs when you do this. this way, no arcing from the coils. compression should read around 175ish.

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    Quote Originally Posted by Rivi View Post
    Stock push rods? or aftermarket?If it was the stockers just replace um and its probably ok.If it was aftermarket push ods your valves are bent.
    These were stocker rods which i replaced with comp cam chromolly rods. It ran fine when started up again and the only reason it sound like crap is b/c the tranny internals are now shot and was knocking really bad. Also the best way is to just take all the plugs out and roll over the motor a few revolutions and read the guage correct?

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    Correct

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    red
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    Quote Originally Posted by fatjet00 View Post
    Correct
    Thank you for your help much appreciated

  10. #10
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    if it runs ok yer alright don't bothrer checkjing it,but next time you will ruin the valves using those new aftermarket pushrods.I use stock push rods OR learn to shift ALOT better. LOL

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    red
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    Well im definitely goin to shift better but i have had clutch problems since i bought the car randomly losing gears and what not. I since put a spec 3+ in and it has the hurst shifter with a short throw and i hate it. So when the tranny comes back im putting a pro 5.0 on and saying to hell with the hurst. Im hoping after the rebuild the engagement will be much smoother and eliminate my shitty shifting .

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