Cummins NHC 250 with dead cylinder...need some experts on the old engines

I've seen that exact same thing happen several times before. The top of the piston melts, comes apart, and aluminum is transferred onto the cylinder wall, into the piston itself, and is pushed out into the manifold.

 

So here is piston #1 from my NHC 250. The liner is scored badly and will need to be replaced.

I'm pretty sure the debris in the crown of piston #2 is piston ring somehow transferred back through the intake manifold and into the other cylinder.

There is a lot of melted aluminum on the small end of the connecting rod that blew through the hole in the side of the piston.

The crank bearings and camshaft appear to be in perfect condition, and the oilpan, and bottom end are spotless.

I have a piston, rings, liner, injector and gaskets coming...about $400CAD. I just hope that this engine has the same pistons it was born with. The parts guy had a dickens of a time following the trail of part numbers, and I can't find anything on the piston, so he went by the numbers on the plate on the side of the accessory drive gear.

Does anyone know the torque values for the head bolts, and connecting rod bolts?

Does anyone have a scan of a service manual for head bolt torquing sequence?

Is there anything else I should know before I really mess things up?

I'm planning on hiring a local mechanic to pull the old liner and press in the new one.

Thanks for the help...enjoy the pictures.

Phil

 

I'm thinking the head bolts are 250 ft lbs. What head gaskets are you using? I think it is victor that makes a gasket you can get from NAPA that seals much better than Cummins. Good pics. You were lucky. I had one piston melt and take the bottom of the liner down into the pan.

Pull the squriters located above the pan on the passenger side, and make sure they are all in good shape, not clogged, and able to flow oil through them.

It's easy to make a liner puller with a threaded rod and a couple pieces of steel. If you know someone with one, that's easier though.

 

Lube up the liner packing just enough that is will go in easy, but not too much, as excessive oil could expand and cause problems. Also, be sure you blow out all bolt holes before installing bolts. The bolts could hydro lock, and crack the block when the engine warms up.

Install the wrist pin clip exactly as it is in pic #1. If turned on end, it could come out and you will be back where you started.

 

Also drain and clean your fuel tanks to make sure there isnt any stove oil or kerosene in the tanks or lines as that can burn pistons as well, i worked for a guy that put stove oil and kerosene in his tank for fueling trucks in the winter and had to replace pistons and liners. He learned after a while.

 

I don't see any piston cooling oil jets anywhere. The parts people didn't seem surprised when I told them my engine didn't have them. I guess I won't be putting a turbo on this one, then Not that I would anyway.

Also, there was an oil filter mounted in a housing on top of the oil cooler, that made an awful mess when I undid the bolt to get it out of the way of the exhaust manifold bolts. Then I get looking and lo and behold, what I thought was an air dryer hanging on the side of the cab in front of the drivers door, is actually another giant oil filter. Obviously not full flow, because it just has little oil lines going to it. The filter and housing didn't have a drop of oil on them, though, even though the oil lines were hooked up (one from the block, the other going back to the oil pan). How often is this filter supposed to be changed? What about the filter on the oil cooler?)

Phil

 

That is a big bypass oil filter. A small amount of oil is pumped into it from the oil system, and after it is filtered, it drains back into the oil pan. The other filter is in an odd place, but it should be the main full flow filter. I always changed both at the same time. The big bypass filter is usually pretty cheap.

There were no sneezers, each held in by one small bolt on the pass side?

 

Pardon my ignorance, but what is a "sneezer"?

 

Sorry. Oil sneezer is what the liner/piston oil squirters were called way back when.

 

Looks to me like the Injector tip has a bad hole in it and it is spraying the fuel out to the linner. You will need a new kit complete If the linner shows any heavy scuffing like it may have siezed change the rod out also. You should be able to look into the turbine housing and see if the turbine has been damaged on the outside edge. Does this one still have the water cooled turbo?. Fill the intake in the head, with solvent and if it leaks in a stream within 10 seconds tap the valve stem wipe it and try again, then do the exhaust, Just a thought!