Murphey1210

Ok so here's the deal. This is my first LS engine and I'm trying to get familiar with everything. I put this motor (from 1998 corvette) into my 240sx. It was running and driving beautifully until one day I was coming up to a light And it started pouring bluish smoke out the tail pipe. I immediately parked the car and had it towed home. After letting it sit for a couple days, I started it and let it run for a few minutes. The longer it ran the worse it smoked. Did a compression test on all four cylinders and got a high reading of 170 and a low of 155. I then did a cylinder leakage test. This is where I become lost. I put the piston on the compression stroke and got the piston to TDC. I hooked up my tester and applied air into the cylinder. I hear a hissing coming from the oil fill tube. So I believe it to be piston rings failing. I wanted to see how the other cylinders performed also so I did the same for the rest of them. And got the same results from every cylinder..... So am I doing something wrong with my test or did mess up all the rings?? This is a ls1 from 1998 corvette. Guy I bought it from said it had "80k" miles but who really knows. Any help would be appreciated!!!

RonSSNova

iTrader: (3)

Did you move the piston in each cylinder ever so slightly around TDC when doing the test?
Doing that squares the rings in the bore and seals them better.

I can't imagine all the rings failing suddenly.

I'd be tempted to carefully check the PCV system. Maybe even pull the intake manifold and see how much oil is in the ports.

Plugs all oil fouled?

RockinWs6

Before you do anything else try this: Start the engine, pull off the oil cap with it running and see what it does. If you have broken ring lands etc it will be huffing out the oil filler hole. Then use the proper leak tester to find which cylinders. The leak tester will show you how much each one is leaking. I had 150 compression on a cylinder that had broken ring lands so compression isn't that all telling.

raceman14

I am guessing there was a problem with the timing on the engine and the fuel you were using. Lean conditions will easily break ring lands on Hypereutectic pistons.

What did you set the timing at? Were you using the ECU as it came out of the vette???

What were your leakage numbers on the cylinders you tested. Normally you pump in 100PSI and then see what the other gauge reads and it will be 95-100 for good and 90-95 for running ( but worn out to me ), lower than 90 indicates pretty worn out but still running.

You can listen to where the leak is coming from to see what is wrong. It will be intake ( i-valve ), exhaust ( e-valve ) or dipstick ( Rings ).

Mark@AlienChassisDYno.com