compression test results
07-14-2019, 01:18 PM
#1
Staging Lane
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compression test results 2001 camaro ls1 with 241 heads
Did a compression test because I had blue smoke coming from exhaust and possibly oil coming out of the exhaust.
Compression was done with WOT while cranking and cylinder 8 seems to be lower than all of them 148 PSI. Have not check the valve steam seals but decided to do the test 1st. Can someone please let me know if the compression test is alright I dont have ls1 compression specs and not sure if my results are ok.
Bought this motor from someone and was told it was good and had a cam but sounds pretty stock and now blue smoke.
Compression test results
Cylinder 1 150 PSI Cylinder 2 155 PSI
Cylinder 3 150 PSI Cylinder 4 167 PSI
Cylinder 5 165 PSI Cylinder 6 167 PSI
Cylinder 7 160 PSI Cylinder 8 148 PSI
Please let me know what you think,
Did a compression test because I had blue smoke coming from exhaust and possibly oil coming out of the exhaust.
Compression was done with WOT while cranking and cylinder 8 seems to be lower than all of them 148 PSI. Have not check the valve steam seals but decided to do the test 1st. Can someone please let me know if the compression test is alright I dont have ls1 compression specs and not sure if my results are ok.
Bought this motor from someone and was told it was good and had a cam but sounds pretty stock and now blue smoke.
Compression test results
Cylinder 1 150 PSI Cylinder 2 155 PSI
Cylinder 3 150 PSI Cylinder 4 167 PSI
Cylinder 5 165 PSI Cylinder 6 167 PSI
Cylinder 7 160 PSI Cylinder 8 148 PSI
Please let me know what you think,
07-14-2019, 02:51 PM
#2
That's about a 12% spread between the weakest and strongest cylinder. You typically want to see them all within 10% of each other. I don't think that would be the cause of oil burning though. When does the smoke occur?
Was the engine warmed up well before starting the tests? Were all of the spark plugs removed from the other cylinders during testing or just pulled one at a time?
Was the engine warmed up well before starting the tests? Were all of the spark plugs removed from the other cylinders during testing or just pulled one at a time?
07-14-2019, 04:22 PM
#3
standard practice would be
-Add oil (recommended dose) to #8 see if compression comes up indicating ring seal
-remove head for inspection, renew head on that side to ensure it isn't the valve or gasket leak
My offhanded guesses would be the components inside the cylinder:
1. fairly typical breakage of ringland on #7/#8 piston failure related
2. hmm nothing else really in there... that was easy to diagnose then if it's not the head
thoughts about the low compression state:
From a performance stand point that difference is a problem. If you have any hopes of achieveing the definition of high performance with typical parts (nothing crazy) then the compression should be VERY similar across the board, ESPECIALLY on a motor with mileage. A freshly built could show minor disparity for a while but overall you'd like to see them all even out to the same solid number. And then it will perform exceptionally well, balanced, smooth. An engine is a mish mash of vibrations/frequencies so the more we can do to prevent unwanted disparity and vibration during operation the better the outcome will be, and the emphasis for high RPM engines cannot be understated.
-Add oil (recommended dose) to #8 see if compression comes up indicating ring seal
-remove head for inspection, renew head on that side to ensure it isn't the valve or gasket leak
My offhanded guesses would be the components inside the cylinder:
1. fairly typical breakage of ringland on #7/#8 piston failure related
2. hmm nothing else really in there... that was easy to diagnose then if it's not the head
thoughts about the low compression state:
From a performance stand point that difference is a problem. If you have any hopes of achieveing the definition of high performance with typical parts (nothing crazy) then the compression should be VERY similar across the board, ESPECIALLY on a motor with mileage. A freshly built could show minor disparity for a while but overall you'd like to see them all even out to the same solid number. And then it will perform exceptionally well, balanced, smooth. An engine is a mish mash of vibrations/frequencies so the more we can do to prevent unwanted disparity and vibration during operation the better the outcome will be, and the emphasis for high RPM engines cannot be understated.
Last edited by kingtal0n; 07-14-2019 at 04:28 PM.
07-14-2019, 04:45 PM
#4
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Engine is cold when I done the compression test with all spark plugs out. The blue smoke I suspect only happens this when the car is I guess warm, it does it when I step the pedal above 3k rpm
That's about a 12% spread between the weakest and strongest cylinder. You typically want to see them all within 10% of each other. I don't think that would be the cause of oil burning though. When does the smoke occur?
Was the engine warmed up well before starting the tests? Were all of the spark plugs removed from the other cylinders during testing or just pulled one at a time?
Was the engine warmed up well before starting the tests? Were all of the spark plugs removed from the other cylinders during testing or just pulled one at a time?
07-14-2019, 06:38 PM
#5
Cold compression numbers won't tell you much. Drive the car for about 10 miles, get it good and hot, and then do the test. A cold engine with looser clearances and thicker oil will give false readings.