Compression test results!
before he wastes anymore time he should 1st decarbon the engine then do a leak down test. The results will tell him what to do. Purdy simple. Depending on the maintenance done on the car, oil changes etc it may need some work. But doing a leak test with carboned up pistons and rings will not show the true condition of the engine.
Buy one 20oz bottle of techron and add it to your fuel tank then drive it. This will clean everything up to the point you will get real compression readings. Sorry if you guys don't like my advice but i have lots and lots of experience to back me up.
Buy one 20oz bottle of techron and add it to your fuel tank then drive it. This will clean everything up to the point you will get real compression readings. Sorry if you guys don't like my advice but i have lots and lots of experience to back me up.
https://ls1tech.com/forums/generatio...sion-test.html read through this thread, it shows what a clean engine should read.
my 9:1 motor with a turbo cam, was reading in the 100-120 PSI on that gauge, a stock C6 Z06 reads about 150, and a z06 with 11.5:1 CR reads about 170.
my 9:1 motor with a turbo cam, was reading in the 100-120 PSI on that gauge, a stock C6 Z06 reads about 150, and a z06 with 11.5:1 CR reads about 170.
It could just be the gauge, no two are the same. As long as they are all within 10% you are fine and there are no blatant low or high numbers.
You could buy some GM Top Engine Cleaner and run that through the system and maybe clean up any carbon build up in the valves.
You could buy some GM Top Engine Cleaner and run that through the system and maybe clean up any carbon build up in the valves.
My 347 with 11.5:1 SCR and my 223/227 110LSA torque cam made 250psi cranking compression and ran every day on 93 octane. It also made torque like a stroker. It's all in the tune. Compression this high can live on pump fuel.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
TECH Apprentice
Joined: Jul 2006
Posts: 326
Likes: 7
From: Columbus,Ga
i think we need some more info on how the test was done. i was tought to have the throttle blade wide open, battery fully charged, all spark plugs removed (this could explain why cyl #1 is low if all the other plugs was in), etc.... like someone said up top^ don't get to caught up in psi #'s they should be within 10-20% of each other no two engines will test the same all the time. there is alot more to compression testing i just don't want to write a novel. if the engine had that much carbon build up it should be pinging like hell and show alot of knock retard.
From your readings I can honestly concluded that you have a faulty flux capacitor.
Average readings on a Stock LS motor that I have seen have been in the 180 - 190 range.
Your Compression numbers are "Normal" and are within acceptable range.
Average readings on a Stock LS motor that I have seen have been in the 180 - 190 range.
Your Compression numbers are "Normal" and are within acceptable range.
Last edited by bigboykilroy; Oct 19, 2009 at 09:48 AM.
i think we need some more info on how the test was done. i was tought to have the throttle blade wide open, battery fully charged, all spark plugs removed (this could explain why cyl #1 is low if all the other plugs was in), etc.... like someone said up top^ don't get to caught up in psi #'s they should be within 10-20% of each other no two engines will test the same all the time. there is alot more to compression testing i just don't want to write a novel. if the engine had that much carbon build up it should be pinging like hell and show alot of knock retard.
So if my numbers seem acceptable, what would cause it to burn oil, and put out a big blue cloud under WOT, am I looking at valve seals for sure?
Banned
Joined: Nov 2004
Posts: 196
Likes: 0
From: Easley, SC
When I did a compression test on my car, they were all in the 230's. I just attributed it to a combination of a bump in compression with milled heads and thinner heads gaskets along with the stock cam that has no overlap. I guess it was carbon build up all along!
I've checked MANY MANY engines that had 190+ compression readings that read 160 after decarboning the cylinders. Go to GM any dealership and ask for their decarbon service and ask why they would bother to do it if it wasn't a HUGE PROBLEM.
I'll betcha stock LS1 in excellent shape will measurse in the 160 range same with the LS6, the ZO6 maybe in the 175 range.
I'll betcha stock LS1 in excellent shape will measurse in the 160 range same with the LS6, the ZO6 maybe in the 175 range.
