What constitutes "Knock."

[charbles]

I'm looking at a "dream" truck for me... '89 W350 dually 4x4 5sp with a pto dump. 149k, salvage title but looking very dapper, no rust, $7K, etc. etc. Sound like a good deal? Anyway, the REAL question is... this truck has a definite pop, or knock in its cycle, much louder than my truck now. What could this signify? Any input appreciated,
Mike

[KTA]

Price sounds awefully strong to me. I need a better description of your "knock' to have any chance of identifying it. is it speed related? sound like all cylinders or just 1? Coming from the top or bottom end?

[charbles]

I might bring him down a bit, but everything is looking really nice on the truck. Anyway, the "knock sounds like its in one of the six cylinders, as its blended in with the engine.. it's in the same rythem as the engine.

[eyoung429]

For $7k I don't think the owner will have a problem with you taking a long screwdriver (24in) and place it outside the cylinders against the block and listen to it run, then take and use it on the head and see if you can distinguish where the noise is coming from.


unless you have a pair of stethescopes

[moab4x4]

When I bought mine, the knock would change from time to time in intensity. It kinda came and went. When I blew the HG I pulled the head and found that it had stuck 3 or 4 pistons and had scored the cylinders. One was really loose in the bore. I suspect that was my sound.
Check blowby. I could see oil haze wafting from the oil fill on my truck before the HG went. My Cummins mechanic told me that it was worn, but no harm in running it like that. I think he was right. I think the truck got way overheated in its prior life. The lower radiator hose connection to the radiator had been resoldered.

I digress. Check blowby and see how consistent the knock is.
Ken