I have a stock engine with about 120,000 miles. It has about 400whp and it been at that power level for most of its life.

Cylinders1-3 have 170 psi and cylinder 4 has only 135 psi. If I add oil in cylinder 4 compression will shoot up to about 165 psi. So I assume the rings are worn.

The car ideals and drives fine. How serious is this and how much longer can I drive the car? Is this a ticking time bomb?

 

It is not impossible that one cylinder would wear more than the others but this causes me to think that the low cylinder is running lean. So, I would suggest looking at the fuel injector.

 

Can you do a leak down test? If so see if you hear air escaping from exhaust, intake or crankcase. Is the car visibly burning oil from the tailpipe?

 

The car does not burn oil or smoke. I did do a leak Down test and cylinder 1 is leaking a a out 10#. Cylinder 2 and 3 is leaking about 5%. Cylinder 4 is leaking about 35%!!! From what I can tell it seam like its warn piston rings.

 

Sounds like you coul use some fresh rings

 

The compression isn't the worst I've seen thow

 

My question is how safe is it for me to push the car. Should I still be taking my car to autocross and such.

 

If you want to get some more miles out of the car until a rebuild, i would try not to "beat" on it. But if you're just waiting for something to happen before pulling the trigger to do the rebuild, then just drive it how you would any other time. Sounds to me the rings are worn on that cylinder like others have said. Good luck.

Aaron