Can you see anything wrong with this picture?

[jshuman]

Hey guys,
I've had a problem with low cmpression in cyl 3 (147psi) in my 92 gsx. All the others are 178psi. They are ross 8.3:1 pistons. I bought the car with the bottom end already built from a friend. He originally had the copper hg from FFWD on it, but had severe overheating problems and for some reason continued to drive the car until the head warped. At least that is what it looked like when we pulled the head for him because the the hg looked like new still.The car sat for 18 months before I had time to start working on it.

Anyways, out of my own stupidity I bolted a used built head on it with a cometic gasket and afterwards found the low comp on cylinder 3. I am about to pull the motor and fix some issues. I am hoping its an issue with the head and not the bottom end. I am going to do a leak down test this weekend, but I was wondering if some of you experts could look at this picture from back before I put the head on and see if you can see any signs off bad rings? I've seen a few threads where Bogus and JAM were able to point out some issues from looking at pics of the cylinder walls.

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[BogusSVO]

Pull the cams from the head and fluid test the valves.

The "how to" is in the link list in my sig line.

From what little I can see of the cylinder bores, I do not see anything wrong at this point.

Also so in the link list, there is a "How to" for checking for pinched rings.

 

[jshuman]

Thanks a lot! I'll check out those articles.

 

[jshuman]

I've read all of those articles and definitely learned a lot. I'm going to try to get the motor out this weekend. I want to check the mating surfaces of the head and block for straightness when I do the tests on the head and rings, but I do not have a machinists straight edge. Can I pick one up from an auto parts store or do you recommend ordinging one from somewhere?

 

[johnnytsi]

Summit Racing carries several choices for a reasonable price.

 

[fun kart kid]

Goodson also has them and a lot of other machine shop supplies.

 

[JacksonAuto]

Before you tear an engine apart you should ALWAYS do a leakdown test. That is the best diagnostic tool and will tell you which part of the engine is leaking. Either the valves, rings or head gasket.

Judging from the picture, the cylinder walls look way too smooth. Was the block bored and plate honed, or did someone just drop in a set of standard pistons?

Also, were the block and head milled or decked? If not, then that could be your problem as both copper and Cometic gaskets require a surface finish of 50RA or finer or they'll leak.