WideOpenThrottle

This is what I got!

1-155 2-210
3-190 4-210
5-175 6-180
7-165 9-170

I know this is not good. What are your thoughts? Its a 1998 ls1 engine with 94,000 miles on it. What do you think? should the block still be good and just rebuild it with new parts. Or just scrap the block?

Thanks all

Mark

SlickVert

iTrader: (5)

Sometime carbon build-up my cause the valve not to seat good and leak out compression.
If it was my car here is what I would do.
Do a top engine cleaning.
Recheck your compression check and if a cylinder is low stake the valves in that cylinder by connect about 80psi of air into the cylinder then take a rubber mallet and hit the top of the valve stem, it will sound like gun shot. This will blow off any carbine off the seats.
That is will usually fix the problem.
Bob

SUTTERERMAN85

iTrader: (42)

i would think that it is not carbon build up cause some of the cylinders are ok and others are quite low. do you burn alot of oil? does the car run ok and not miss any? this is just my .02

SSDriver

iTrader: (2)

recheck the cylinders that are low and then remove the hose from the spark plug hole and squirt some oil into the cylinder and recheck. If you get a much higher reading its your rings/piston. If the reading stays roughly the same its a bent valve/pushrod/ or collapsed lifter. Good luck hopefully this will tell you a little bit more about the problem. Because its more than just 1-2 cylinders I'm guessing its your rings. Also I would not junk the block you can always use it as a core or re-sleeve it for some much bigger

-William

eallanboggs

iTrader: (1)

The odd bank looks pretty good except that #3 is quite high relative to the other three on that bank. The other way of looking at the odd bank is that #3 could be OK and numbers 1,5 and 7 are all bad on that bank. I'd opt for the former. Then you look at the even bank. There is a greater disparity on that side. After you do the wet test you'll know more, but that is quite a wide difference between your high and low numbers on the even side. Were it not for #3 I'd say the odd bank was OK, but when you take that cylinder into consideration it looks like you have problems on BOTH sides. A difference of more than 10% between your high and low readings usually indicates a problem, but when you compare bank 1 with bank 2 they look like they came from two different engines. Cy #3 looks like it belongs with bank 2 and cy #8 looks like it should go with bank 1. That's why I said you might have trouble on both sides.

Var

iTrader: (1)

Damn you got a V-9!!!

I 'd settle for 170 in my 9th cylinder.

kidding aside it wouldn't hurt to do a top cleaning like suggested. Then do another compression check

WideOpenThrottle

Thanks all. I will look more in to it today!

MadBill

I'm not familar with LSx compression readings, but 210 sounds high for a stock engine. Maybe the high cylinders have carbon build up. If you don't have a leakdown tester available, maybe you could just pressurize each cylinder as above and check for presence/location of air escaping, i.e. exhaust, intake, oil filler..

ExceSSive

iTrader: (13)

What should the pressures read on a stock LS1...10.1:1 or LS6...10.5:1?