Last night I was able to get the 1997 506 engine disassembled to see what was up inside that motor. It was running when I pulled it out of the C3500 truck it was in several years ago, but had almost zero compression on one cylinder and was missing.

Turns out the engine must have ingested a glow plug; the piston top was beat to heck and the exhaust valve was damaged with a chunk missing out of it:








I put a light in the exhaust port.... there shouldn't be light shining out behind the valve!






The rest of the engine looked great! No cracks that I can see. The cylinders still show the cross-hatch marks:





The only issue I have found so far is that the cylinder with the damaged piston has some very light scoring:






My plan is to remove that piston and hone that cylinder to see if it will clean up. If so, I will then use this short block, swap a piston in from my 95, use my 95 heads, install new bearings, rings, and headgaskets, swap over my nearly new water pump and timing chain from the 95, and then I should be good to go.

Casey