PLEASE: Help me Diagnose this Problem(No 56k)

[JT87NA]

Well I pulled my engine today and pulled the head off. For now I am just looking at cylinder 3 since the compression was 60 psi and all other cylinder were at 180 except for cyl 6 which was at 155 dry 175 wet. I also did a leakdown test and the normal cylinders were at 15% leakdown, number 3 was at 80% leakdown and I could hear air escaping through the pcv system and oil dipstick. I figured I would pull out a piston that was either melted, broken rings, or collapsed ringlands. I didn't find any of these problems and there is still crosshatching on the cylinder wall. There is some scuffing on the side of the piston near the top. Give me your opinions, and also what caused this? Thanks.


BTW: This is a 1/2 NA-T conversion. Later.

Here is a pic of the scuffing on the edge of the piston:

I will take pics of the cylinder tomorrow because I can't get a good shot right now with the lighting in my garage.

 

[chevyeater]

That is a pretty fuzzy pic but, the piston doesn't look too healthy from what I can see. Would your fingernail get stuck in the marks above the top ring if you were to run it over them?

 

[JT87NA]

That is a pretty fuzzy pic but, the piston doesn't look too healthy from what I can see. Would your fingernail get stuck in the marks above the top ring if you were to run it over them?

Yes my fingernail will get stuck in some of the larger marks.

 

[JT87NA]

Better Pics, Hope these help.

 

[chevyeater]

Yup, that's a paperweight. Maybe went lean?

 

[Bishop92t]

That's really strange looking. Detonation usually causes the ringland to break. What does the top of the piston look like?

 

[JT87NA]

That's really strange looking. Detonation usually causes the ringland to break. What does the top of the piston look like?

Top of the piston looks normal, I should probably just take the block and piston to an engine builder and see what he has to say. This engine is under warranty under ATK and I need to know whether it was my fault or theirs. If it was in fact their fault I can send the longblock back and they will send me a new longblock if it is my fault(ie detonation) then I will just rebuild it myself. Would it be ok to just swap a new piston in with new rings into that cylinder?

 

[JT87NA]

Top of Piston...

 

[Bishop92t]

The way the top of the piston looks makes me suspect something is wrong with your head, leaky valves, injectors?
So long as the cylinder walls aren't scored up you should have no problems setting a new piston and rings in there.

 

[JT87NA]

Detonation...I was tired last night and just figured I would see a blatant crack in the ringlands, guess detonation likes to hide . I found two hairline cracks this morning under the second piston ring from the top. I will try to take some pics of the cylinder wall.

 

[lagged]

looks like you might need a valve job.

 

[JT87NA]

looks like you might need a valve job.

Why is that?

 

[lagged]

the top of the piston looks wet. the valve seals are probably leaking.

actually i missed it before, see bishop's post two before mine. he addresses the issue.

 

[Bishop92t]

I took a second look - assuming those pistons were installed correctly, that is really strange to see the clean overheated area on the intake side, and on cylinder 3. I'd be more worried about the problem reoccuring then how to rebuild. I would get the head pressure checked, checked for cracks, and check the injectors for proper flow. How does the underside of the head look at #3?

 

[JT87NA]

I took a second look - assuming those pistons were installed correctly, that is really strange to see the clean overheated area on the intake side, and on cylinder 3. I'd be more worried about the problem reoccuring then how to rebuild. I would get the head pressure checked, checked for cracks, and check the injectors for proper flow. How does the underside of the head look at #3?

Under side of the head in #3 looks like all the others look, normal carbon buildup.