Compression Test Results LT-1
Thread Starter
Burning Brakes
Joined: Aug 2007
Posts: 1,084
Likes: 8
From: Illinois
Compression Test Results LT-1
Had a compression test done at a local shop and it turned out the valve seals were bad--had them replaced. My question is when the mechanic gave me the compression test results the numbers seemed high compared to the compression test results I have seen listed by other forum members. Here are the numbers--do they seem high or is this normal for a 71 LT-1? Car runs great now that the but was loosing oil via the valve seals.
#1 185
#2 190
#3 180
#4 190
#5 175
#6 175
#7 185
#8 190
#1 185
#2 190
#3 180
#4 190
#5 175
#6 175
#7 185
#8 190
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
Per the Chevrolet Service Manual, cylinder compression for 1971 LT1 engine should be 150 psi (with no more than 20 psi variation between all eight cylinders). The 'method' of measuring engine compression might be different between your mechanic and GM. Your readings are consistent...which is a good thing.
Melting Slicks
Joined: Apr 2001
Posts: 2,030
Likes: 363
From: Lubbock Texas
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
I use a cylinder leakdown tester (pressurized guage using air compressor) that is much more accurate than cranking compression for determining cylinder leakage. Numbers seem high and too consistant unless engine has low mileage on it (did he really do a leakdown test of all 8 cylinders?) You should go to umbrella type guide seals for a Ford 289 motor instead of the poor design of the Chevy "O" rings.
