1G Compression test results question

[krusieski]

Hey guys Just had a quick question. I ran had a compression test done. I drive a 92 laser turbo fwd 122k. The numbers were cyl 1 129 cyl 2 82 cyl 3 121. Cyl 4 152. I understand cyl 2 is low I'm going to be taking head off and taking a look and possibly the block and pistons. I was just wondering if anyone has seen similar numbers and have seen the problem? I'm thinking valves, piston ring or wall or maybe a head gasket? It does leak oil so any info would be great thanks!!

 

[303_2G]

Where does it leak oil from?
A leakdown test will expose the culprit but something quick you can do is squirt a little bit of oil in the spark plug hole on the low comp. cylinder and if the comp. test results a higher pressure it's gonna be the piston rings.

 

[krusieski]

Ok thanks man !

 

[303_2G]

If nothing changes do the leadown test and listen to the intake or exhaust manifold to hear if air is leaking and then you know it's the valves.

 

[nickfromfortfun]

I second a leak down test. I sure hope its simply valves and not rings it would be an quicker and easier fix for you.

 

[hotrodssnova]

You have to remember that we have dished pistons. The only way to get oil on the rings is to put that cylinder at bottom dead center and use a flexible delivery device that will go in the cylinder and put the oil on the cylinder wall and edge of the piston.

 

[krusieski]

Ok did a smoke test and stuff. It passes. No leaks vacuum or boost

 

[evil_eagletalon]

the way I look at things when doing a compression test is.
1 compression test
2 if 1 cylinder is low I add a table spoon of engine oil into low cylinder.
if compression rises I point fingers at Rings if it does not raise I say possible valve train issue.
3 cylinder leak down test.
Rent/buy a leak down tester. set tested cylinder to compression stroke top dead center. Watch leakage perecentage. Next listen for air from areas like exhaust.throttle body,Radiator,Diptstick,

Dipstick= oil control rings
Throttle body= intake valves (bent)or valve seals
Exhaust (bent valve) or valve seals
Radiator=blown head gasket.

 

[krusieski]

headgasket was riped by cylinder 2 so im wondering if thats whats causing low compression in that cylinder ?

 

[evil_eagletalon]

was it overheating? If not I don't think the low compression is due to the head gasket.


Before you go spending money on anything. Put that head back on with the old head gasket, torque it to specs and do a leak down test buddy.

This will narrow it down pretty good. Then start replacing parts. (DONT REUSE THE HEAD GASKET ONLY FOR LEAK DOWN TEST)

The last thing you want is to replace head gasket,machine head,valve job etc etc and you still have low compression due to piston rings.