VinhZXT Posted April 6, 2010 Share Posted April 6, 2010 Guys, I am about to buy an LS1 motor off a friend. The compression readings are not what I expected. A coupld cylinders have low readings and a couple have very high readings. Please tell me whether it is safe to buy it. Cylinder #2 reading is 150 dry and 175 wet. Cylinder #3 is 165 dry and 200 wet. Cylinder #5 is 225 dry. Cylinder #7 is 215 dry. The rest of the cylinders are around 175. Thanks for any info in advance. V. Quote Link to comment Share on other sites More sharing options...
Cable Posted April 6, 2010 Share Posted April 6, 2010 I am not sure what you mean by 'wet' or 'dry'. Quote Link to comment Share on other sites More sharing options...
blueshark123 Posted April 6, 2010 Share Posted April 6, 2010 I am not sure what you mean by 'wet' or 'dry'. When you do a compression test you want to do it dry first. Then you do a wet compression by pouring oil in from the spark plug hole. This temporarily seals the piston rings. If your wet compression is higher than the dry then that points to worn piston rings. Vinh, cylinder 3 worries me a bit because it is a 20% jump in compression from dry to wet but LS1 motors are known to have wacky compression readings from the factory. Do you know how many miles are on the motor? Quote Link to comment Share on other sites More sharing options...
RB30X Posted April 18, 2010 Share Posted April 18, 2010 When you do a compression test you want to do it dry first. Then you do a wet compression by pouring oil in from the spark plug hole. This temporarily seals the piston rings. If your wet compression is higher than the dry then that points to worn piston rings. Vinh, cylinder 3 worries me a bit because it is a 20% jump in compression from dry to wet but LS1 motors are known to have wacky compression readings from the factory. Do you know how many miles are on the motor? So what if your LS1 had all cylinders around 135-140 dry and 140-150 wet?? A lot lower than some peoples readings (200psi) but kind of close together. Quote Link to comment Share on other sites More sharing options...
rags Posted April 18, 2010 Share Posted April 18, 2010 (edited) So what if your LS1 had all cylinders around 135-140 dry and 140-150 wet?? A lot lower than some peoples readings (200psi) but kind of close together. For a motor with a cam that has more overlap than a stock cam, this would seem perfectly normal. Vinh, How long has the motor been sitting? Are you spinning it the same number of revolutions for each cylinder? Sounds like some of the lifters have bled down causing some of the high readings. Joe Edited April 18, 2010 by rags Quote Link to comment Share on other sites More sharing options...
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