Compression test question?

**MasonWS6** · 08-30-2015, 12:36 PM

So I just finished a compression test on my ls1. The driver side cylinders all came up to be 175 psi. The passenger side however only cyl #8 & #6 came up to 175psi. 2 & 4 came up 150psi. I did cyl #2 twice. The first time it came up to 130, second time was 150. I am trying to see if I have a bad head gasket. 150 from 175 doesn't seem like a drastic drop but then again I'm loosing coolant slowly. I guess what I am trying to ask is what should be the standard psi. Also should I check the intake manifold?

**pajeff02** · 08-30-2015, 01:07 PM

There is no coolant crossover on an LS1 so the intake would have nothing to do with a loss of coolant.

A couple of more tests that you can complete. Squirt about a tablespoon of clean engine oil into each of the cylinders that tested low and the repeat the test. If the compression jumps up it is likely that you have an issue with the rings or cylinder walls. If the compression stays low, then you have either a valve issue or head gasket issue. Is the engine overheating? Another thing you can do is pressure test the cooling system. You can "rent" a tester from a chain parts store and see if the cooling system loses pressure. Have any friends with a bore scope?

**MasonWS6** · 08-30-2015, 01:33 PM

Ok thank you, I'll try the oil trick. And no the engine is not overheating but did start puffing white smoke that smells like burnt antifreeze. There's no visible leaks on the motor

**pajeff02** · 08-30-2015, 02:29 PM

Let us know what you find.

**2002ssslp** · 09-02-2015, 05:29 AM

Originally Posted by pajeff02

There is no coolant crossover on an LS1 so the intake would have nothing to do with a loss of coolant.

A couple of more tests that you can complete. Squirt about a tablespoon of clean engine oil into each of the cylinders that tested low and the repeat the test. If the compression jumps up it is likely that you have an issue with the rings or cylinder walls. If the compression stays low, then you have either a valve issue or head gasket issue. Is the engine overheating? Another thing you can do is pressure test the cooling system. You can "rent" a tester from a chain parts store and see if the cooling system loses pressure. Have any friends with a bore scope?

Wet compression test. Kicking it old school. I like it.

**pajeff02** · 09-02-2015, 07:07 AM

That's how I roll, dawg.

**MasonWS6** · 09-08-2015, 12:39 PM

So the compression test is leaning towards head gaskets. I tore everything down to the heads and I'm going to have someone with more experience to take them off, make sure the heads are straight and put the new gaskets on

**pajeff02** · 09-08-2015, 05:36 PM

Any pics of the project?

**MasonWS6** · 09-08-2015, 05:41 PM

This is as far as I got

**MasonWS6** · 09-08-2015, 05:45 PM

Attachment 26379 Attachment 26379 Attachment 26379 Attachment 26379 Attachment 26379

**pajeff02** · 09-09-2015, 09:30 AM

Mason - upload your pics to a free photo sharing site like Photobucket or Image Shack. Once uploaded, simply copy and paste the [IMG] code for each photo into your post on here.

**2002ssslp** · 09-13-2015, 03:10 PM

I can't get the pictures up.

**WillieNams** · 03-17-2016, 02:17 PM

Adding oil to a motor with dished pistons just raises the compression ratio, a leak down test will tell you where the compression is going. It could be a problem with how your crank vents are hooked up or valve seals also. Turbos can leak oil also.

John