I have an engine that has sat for a couple years and I had the itch to finally tear into it this weekend. The engine has roughly 6k on the rebuild but it had trouble making any boost (I bought it for a parts car). I did a compression test before the engine was pulled and one of the cylinders was slightly lower than the others. Unfortunately, I cannot find my notes on what those test readings were. I do recall it was either cylinder 3 or 4 that was low.

The previous owner installed Keith Black hypereutectic pistons with the rebuild. Something happened and he thought there was an issue with the piston rings. Being hypereutectic pistons I was expecting to see some sort of failure when I pulled the head off this weekend. However, it was pretty mundane and no cool carnage.

However, here is what I noticed:
  • I drained the oil and although the oil had very few miles on it (maybe 10) there was a good amount of mucus like sludge that came out at the beginning and towards the end. The head gasket (Fle-Pro) showed no signs of failure. Could this just be moisture from sitting for a couple years? I let some of the sludge gather on my engine stand and took a picture of it.

https://drive.google.com/file/d/1NxV...zawMIpuv0/view


  • Cylinders 2 and 3 had build up (carbon?) on the intake valve, all other valves looked smooth. Cylinder 3 was the worst, see pic. What is this buildup and what causes it?

https://drive.google.com/file/d/1Ied...mfYigLSgT/view


  • The cylinders looked great except cylinder 3 had some build up at the top of the cylinder. Possibly surface rust, it looks similar to the build up on the valve. Other than that each cylinder has very nice cross hatch.

https://drive.google.com/file/d/1Cs0...VKjsFQ0Tq/view


  • There was a black flakey film on 3 of the 4 cylinders. What is this? Is this just poorly combusted fuel?

https://drive.google.com/open?id=1GV...HFnWPMO8FgsRmd

I measured the bores with a caliper, which doesn't seem like the right tool. Anyway, each cylinder was ~3.47" so 0.030" over?

The engine had no knocks or rattles, it sounded fine it just wouldn't make boost and has the hypereutectic pistons. I was hoping to just pop in new forged pistons without disturbing the crank or completing a full rebuild. Thoughts on if this is wise based on the pics? Should cylinder 3 be rehoned to remove whatever is at the top of the cylinder? Should I purchase new rod bearings or can these be reused if they look to be in good shape?

I have plenty more pictures of each cylinder if it helps. I don't remember how to post images directly in a forum post though, or at least it isn't working for me from Google Drive.

This is a new learning process, and a bit of a relearning process, for me as I have stepped away from working on cars for a few years now.

Thanks,
Ryan