Engine will not turn

[WhiskeyTeef]

Ok I was wondering how you were turning a diesel engine by hand on the flywheel!! They are tight to do that once they hit compression. I've lost a bunch of knuckle skin on flywheels in the past. Did you pull a main cap to see if there is any scoring on the bearings or main journals? Can you see scoring in the cylinders?

I didn’t see any scoring on the cylinders. Nothing seemed burnt, cracked or broken. No discoloration. Metal with residual oil on it. Nothing caked or baked on. I can’t get to the cam bearing so I’m not sure who said it above, but if we don’t see the engine free up in the next week, that is likely the culprit.

 

[87cr250r]

So I've only opened 3 GM engines, a 350 a 6.2 and a 6.5. The front cam bearing certainly takes a brunt of the wear on those engines I have opened.

You can't really judge oil starvation from the cylinders. They're the last to be affected. I strongly suggest checking mains and rods. At least slide the rod big ends fore and aft on the crank pin. They should move freely for and adr and have no perceptible movement side to side.

You can drop main cap. The lower shell wears first unlike the rods which wear the upper. My experience of 3 engines has shown the most wear at the rear main. The 6.2 and 6.5 engines use trimetal bearings on the mains and may show an alarming amount of the bronze backing but aren't worn out. I'm personally not a fan of the trimetal bearings.

 

[Buck69]

Does the crankshaft have end play? It is something else that is easy to check and very important. My experience is with larger diesels and I have seen crankshafts tighten up on running engines from both breaks and bends.
It could also help to identify if something in the transmission is loading up the engine.

 

[87cr250r]

Good point on end play. That can be checked without disassembling anything. Pry on the damper of flex plates. You should get an audible thunk in each direction as the crank hits the thrust bearing.