posting for a friend:

we did a compression test last night on his c5 motor. here's what the numbers were:

210
125
210
210

what do you guys think can be the problem? i checked his valves and they were very lose. i did a valve job and set the intake to .007 and the exhaust to .008. i put a cap full of oil in the #2 cyl and the compression went up to 210 like the others.

the car isn't over heating, no smoke out the exhaust, no oil on the plugs, no coolant in the oil, no oil pressure light.

any ideas on what could be wrong with his motor? he's thinking its a bent valve, but how do you tell if you have a bent valve? when at idle, his car does sound kinda funny when you listen to the exhuast.

 

intrested in selling?


another hatch needs a c5

 

Ring broke

 

yeah, thats a classic case of ring problems. But you sound intelligent enough about the situation to know this already. i think you are just looking for someone to give you a magic answer thats NOT the rings. so here goes (seriously)

1. head gasket
2. warped head
3. ok i only got 2....

 

just wondering if its a ring or bent valve.

how can you tell if you have a bent valve?

what will happen the car continues to be driven like this?

 

If it were a headgasket or warped head then #1 or #3 would have low numbers in addition to #2.

 

not exactly true, i had a little headgasket problem on a GSR a few months ago and oddly enough, cylinders 1,2 and 4 were at 220psi while cyl 3 was at 110.

 

not trying to be argumentitive, .rj is right, most likely other cylinders would be low as well. Do a leak down test, this will tell you whats wrong. But from your description of adding a little oil and having the comp numbers shoot up, it sounds like rings.