Cummins 3.3

[barklee]

So as you can see we have a problem here..... This motor is in a Snorkel TB 66J lift. It was smoking really bad and determined that the #2 cylinder was losing compression. I figured it was a bad injector, but was quickly proven wrong on that! We removed the head and had it pressure tested, came back fine. I happened to notice that at the top stroke the #2 piston was about 1/8" lower than #3. Crazy, as big as these rods are that they would bend like that and still the engine runs without catastrophic failure.....
I was hoping to see if anyone has torque specs for this engine? I gotta order a new seal kit and rod Monday so it will be a few weeks before parts arrive. Any help would be great.

 

[DB2]

Any idea why the rod bent?

 

[lantraxco]

Only thing I have seen can do that without other obvious mechanical damage is hydrolock-liquid in the cylinder when starting, or way too much ether. I would at least replace the piston as well. If it's not a huge pain, pull the crank and have it magnafluxed, you may find that rod throw has fractures from whatever huge force it took to put that rainbow curve in that rod.

:my2c

 

[DB2]

Only thing I have seen can do that without other obvious mechanical damage is hydrolock-liquid in the cylinder when starting, or way too much ether. I would at least replace the piston as well. If it's not a huge pain, pull the crank and have it magnafluxed, you may find that rod throw has fractures from whatever huge force it took to put that rainbow curve in that rod.

:my2c

Yes Id be concerned with the crank as well.

 

[barklee]

Yes Id be concerned with the crank as well.

My guess was hydrolock. I think the head gasket blew and filled the cylinder with coolant. Although i couldnt see damage to the gasket, something polished the piston.
I was really hoping you wouldnt say to be concerned with the crank! To the common eye it looks good....If i put this back together and run it, what could happen besides it breaking?

 

[td15c]

I had this happen on a 453 Detroit in a trencher. same thing it smoked, missed on one cylinder, so adjusted valves then changed injector still missed. It ended up being a bent rod. What I found was a peace from the top of the exhaust manifold gasket had blown out, and water off a crack in the hood ran right on top of the manifold and was able to get in it in a hard rain witch caused a hydro lock and bent the rod.

 

[lantraxco]

My guess was hydrolock. I think the head gasket blew and filled the cylinder with coolant. Although i couldnt see damage to the gasket, something polished the piston.
I was really hoping you wouldnt say to be concerned with the crank! To the common eye it looks good....If i put this back together and run it, what could happen besides it breaking?

If the top was clean, it's almost certainly water, or as you say coolant. A small leak in the gasket may not be something you could see easily.

I think you answered your own question about the crank... if the stress caused a bend or fractures, then eventually the crank will break, possible causing damage to the bock, valves, head, etc. Heard of an old Mack six cylinder that the rod throw broke cleanly away from both ends of the crankshaft, threw the rod out through the side of the block with the throw still in the rod bearing. Fun stuff.