Normal compression test #'s
08-24-2007, 05:17 PM
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Normal compression test #'s Just wondering what stock compression numbers should be? I did a compression test today with a cold motor and I got 155-160ish across the board. Just wondering if those are ok numbers. I tried searching but it wasnt working very well. Thanks for the help.
08-24-2007, 05:45 PM
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Thankyou! I was getting scared finally search worked for me. All the post I was seeing they said there # were near 200# but these were 2000 and up cars. This is a 96 Z28 with 119,000 miles on it. Glad those # seem good!!!
Thanks
Derek
Thanks
Derek
08-25-2007, 12:18 AM
#5
Did you have the throttle blocked open?
Frankly consistent numbers is most important but that said those numbers are quite low but it could just be the gauge.
My wagon at 180K cranked 200psi and my Caprice with the milled heads and thin gasket for 11.2-3:1 compression cranks like 230psi.
On an old low compression gen 1 135-160 might be fine but on an LT1 I do not think so.
Frankly consistent numbers is most important but that said those numbers are quite low but it could just be the gauge.
My wagon at 180K cranked 200psi and my Caprice with the milled heads and thin gasket for 11.2-3:1 compression cranks like 230psi.
On an old low compression gen 1 135-160 might be fine but on an LT1 I do not think so.
08-25-2007, 10:52 AM
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Yes the throttle was open. Maybe if the engine was hot the numbers would have been higher. And this was done with a cheap 5$ gauge so who knows. The car runs good ran a new best last night 12.6 at 111mph 
Only mad 2 passes got there to late. I think with more practice I can get a low 12 maybe high 11. Well thanks for the info.
Derek
Only mad 2 passes got there to late. I think with more practice I can get a low 12 maybe high 11. Well thanks for the info.Derek
08-25-2007, 11:29 AM
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Originally Posted by derekderek
Yes the throttle was open. Maybe if the engine was hot the numbers would have been higher. And this was done with a cheap 5$ gauge so who knows. The car runs good ran a new best last night 12.6 at 111mph Only mad 2 passes got there to late. I think with more practice I can get a low 12 maybe high 11. Well thanks for the info.
Derek
Only mad 2 passes got there to late. I think with more practice I can get a low 12 maybe high 11. Well thanks for the info.Derek
oh yeah btw 12.6 is a decent trap for 111mph if its a 6speed car, you def not touching an 11sec anything with 111mph trap speed.
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08-25-2007, 12:06 PM
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Originally Posted by LittleRedZ
sounds like your car runs well, whats done to it?
oh yeah btw 12.6 is a decent trap for 111mph if its a 6speed car, you def not touching an 11sec anything with 111mph trap speed.
oh yeah btw 12.6 is a decent trap for 111mph if its a 6speed car, you def not touching an 11sec anything with 111mph trap speed.
It has LT headers dumped before the axle, CAI , Wally 225, Nitrous express kit, Spec stage 3 clutch , lighten flywheel, 160 thermostat , And 350-400 pounds of weight reduction! And some suspension work done. Well the 12.6 I bogged of the line still trying to find a good launch rpm with the new ET streets. I know I have a low 12 in it. I also have 4.56 gears waiting to be put in. And if I put Skinny's up front instead of the 275's ZR1's up that should help. Any suggestions? Thanks
Derek
08-25-2007, 12:15 PM
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I would fully warm the engine up if you want more accurate numbers. I was seeing averaged out 205-210 on my 167k engine. Iron heads so the compression is a touch lower than with AL heads.
08-25-2007, 12:32 PM
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Originally Posted by derekderek
It has LT headers dumped before the axle, CAI , Wally 225, Nitrous express kit, Spec stage 3 clutch , lighten flywheel, 160 thermostat , And 350-400 pounds of weight reduction! And some suspension work done. Well the 12.6 I bogged of the line still trying to find a good launch rpm with the new ET streets. I know I have a low 12 in it. I also have 4.56 gears waiting to be put in. And if I put Skinny's up front instead of the 275's ZR1's up that should help. Any suggestions? Thanks
Derek
Derek
you need another 3-4mph to get to 11s that if you get a 1.6 or better 60ft. Get a set of rockers that should pick you up a mph or two and an electric water pump, get a tune from PCMfor less you would be close.good luck
08-25-2007, 12:48 PM
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Originally Posted by LittleRedZ
yeah spray it more you need another 3-4mph to get to 11s that if you get a 1.6 or better 60ft. Get a set of rockers that should pick you up a mph or two and an electric water pump, get a tune from PCMfor less you would be close.
good luck
you need another 3-4mph to get to 11s that if you get a 1.6 or better 60ft. Get a set of rockers that should pick you up a mph or two and an electric water pump, get a tune from PCMfor less you would be close.good luck
What rockers do you recommend? Electric water pump is already on the list I figured I would wait till the opti started showing signs of going out! As for spraying more don't think it would help that much I still need to perfect my driving with what I got now. No need to rush and blow things up just yet
. Derek
08-25-2007, 03:13 PM
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I've got a question. How would you suggest threading a compression gauge into 8 spark plug holes on a hot engine? As tight as it is in there, I don't see myself getting one cylinder done without burning the **** out of my hand.
08-26-2007, 11:29 PM
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im with the above. i use the numbers cold just to get a ballpark average. if you were really concerned with an individual cylinder, then do it warm. just my two cents...
08-27-2007, 01:42 AM
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Those who don't care about doing it with a warm motor, do us a favor and run the tests twice. Once on cold, once on warm/hot, so we can get the % change and apply it to our cars 
