I was going to take my car in to get a compression test done before I do my heads and cam because the car blows smoke at start up. But then I saw I can by the tool for testing compression for only $30, and do it my self.

But I want to know, if a compression test will be able to tell me if the problem is valve seal related or piston ring related? Because this is what I want to know more then anything....

Or is there a better test for that? Or will the compression test tell me what the problem is?

 

If you loose compression in a cyl its not b/c of the valve seals. So yes a compression test would tell you that you have bad rings, only if you have determined that its not a bent valve, or improper seat of the valves. You'd have to do a leak down test for the valves though.

If its blowing smoke on start up, its more than likely the valve seals.

 

cool, i just want to do it, for a insurance more then anything. I dont wanna do the work to the top of the motor and have that problem. I had a bent valve earlier this year. And I got a feeling when they replaced the valve they didnt do somthing right with the seals or seats. Only other time it will smoke is if im in nutrual, and i rev it up above 3k.... but the wierd part is, it dont blow the smoke till I release the throttle. I was told that its most likely because of the suction force, pulling down the oil from the seals or seats, if they are fulty. But no loss of power.... I think im going to order the tool.