benelliwang

I bought an used LS1 engine from an forum member, it was supposed to be in working coindition. The engine looked good and I did a leak down test. Only cylinder 1 registered 5% leak down. All the cylinders registered 30% to 70% leak down. Most of them are leak from the exhaust port and some are leak into the crank. Since the engine was shipped dry, I squirted some motor oil into the cylinders and turned the motor over a few times but I was getting the same result. The engine is drained of fluids when it was shipped. Is there something different I must do on an engine that was crated and shipped?

Please help

kp

iTrader: (34)

you have to have the piston at TDC/compression so both valves are closed on the cylinder you are leaking. Thats kind of a pain to get right so you are better off taking the rockers off and trying it - that way you will be sure the valves are closed - if you havent done that already

benelliwang

The rocker arms were taken off to make sure the valves are closed. I squirted some mobile 1 oil into the cylinders to help seal the compression. The pistons are then turned to TDC and leak down test performed. The oil pan is empty and the engine is currently dry however.

kp

iTrader: (34)

if you did that and its leaking through the exhaust valves, well, its leaking through the exhaust valves. If the engine has been sitting a while you can try tapping the valve with the wooden handle of a hammer or a rubber mallet to see if they 'seal' after a couple whacks. These motors usually leak fairly high through the rings when they get some miles on them but going fron 5% to 60 is a little drastic..

benelliwang

I will try tapping the exhaust valves tonight, thanks

7 cylinders are not holding the pressure... Almost all of them are leaking through the exhaust. Could it be related to long term storage of the engine. It was pulled off the car months ago...

Larry

iTrader: (4)

What size orifice are you using? I used a .040 orifice when I did my leak down and got no more than 4% leakdown on any cylinder.

It was no problem with the rockers on and setting each piston on TDC. I had a helper apply air pressure of 20 psi approximately and I turned the crank until it had no resistance at TDC. Once on approx TDC it stayed when applying 100 psi. Any more than 20 psi and you won't be able to turn the crank at all.