I have good compression on cylinders 1-3 at around 210 psi, but cylinder 4 is only 165. I added a little oil into the combustion chamber and it read normal, a bit above 210. Is it possibile that the rings just aren't line up correctly or do they definately need replaced? The rings only have a couple thousand miles on them, which is why I ask.

Does anyone know where I can get a set of 84.5 mm rings quickly? Should I go with wiseco which is the piston I have, or what?

 

Anyone?

 

Was the engine cold or hot for the CR test? With a cold engine the rings/pistons aren't hot and swelled to fit the cylinder and you get incorrect readings. The CR test is supposed to be done on a warm engine.

 

Right, and that would be even more true with forged pistons. It was on a cold engine (the engine was out of the car). However, I wasn't looking at the actual numbers, just the difference between the numbers. One was defintately quite a bit lower than the others, and adding oil did put it up to normal psi, meaning it was the rings.

 

You got it!