1G Super low compression all cylinders fresh head gasket?

[chuckd]

Hey guys my buddy bought a 91 TSi AWD auto. Anyways it was SEVERELY overheated to the point where the spark plug cover melted and the timing cover melted as well. But anyways, we got the head decked and it was heavily warped says the machine shop and it passed a vacuum test. (without the valves installed).

So we put it all back together with a new head gasket and all and properly timed and it has like 20 psi across the board. This car didn't skip timing it just overheated. Anyways, I hook up the compression tester adapter to a air compressor and there is a lot of air coming out the intake and exhaust. So I took the timing belt off and moved the cylinders to a neutral point and then moved the cams accordingly so the valves are completely shut on the cylinder I'm pressure testing, yet it still leaks. Is it possible that the valve seats warped and just need a heavy lapping?

Also there is some scoring in the cylinders and we were getting pretty heavy blowby while cranking the motor over. (It wouldn't start)

So now we are tearing it back apart and we are replacing the rod and main bearings and rings while we are in there. We are gonna check for bent valves (although no evidence of the valves hitting the pistons) and then we are gonna do a heavy lapping process on it to see if we can get the valves to seat again..

Any input would be greatly appreciated and if you know whats wrong here please feel free to give me a call.

Thanks a lot
chuck

 

[TjPhillips36]

If the vehicle overheated that bad I would have replaced the head personally. And the machine shop should have pressure tested the cylinders with the valves installed to make sure their were not other problems.

 

[Benshooter]

Did you have a temp gauge on the car when it overheated?

 

[chuckd]

bought it after it overheated. got it for 400 bux

 

[Benshooter]

bought it after it overheated. got it for 400 bux

Ok. Either way I would completely go through the engine. You're definately on the right track with replacing the bearings. If you can afford it you might want to replace the hardware as well.

After having an engine get hot enough to melt anything plastic attatched to it I would be nervous about using it again without having everything rebuilt, align-honed, and balanced as a rotating assembly.

 

[NeMiZiS]

If the vehicle overheated that bad I would have replaced the head personally. And the machine shop should have pressure tested the cylinders with the valves installed to make sure their were not other problems.

+1
I feel the same way.

 

[rlacasse1]

+2

You should just cover everything that way you know it is 100%.

 

[rw87tt]

My daughter overheated a 1995 Altima she had. I took the head to the machine shop to get rebuilt and straightened. He suggested that I consider reringing it. Which I did. Good thing too. The rings were stuck to the pistons. I imagine the heat cooked the oil in the grooves and it gunked the rings up in the groves. The rebuild turned out ok. Hopefully your trans is OK. That's one good thing about external coolers.