Engine/Transmission (1994 - 1998) Engine damage

[CumminsPower98]

I looked at a relatives '94 after being pulled from truck and head/pan taken off this week and have some questions. #4 cylinder died with broken valves. Both valve heads came off and the exhaust was broken in 3 places and of course bent the push rod on that one and ruined the cylinder and piston of course. All 6 exhaust valves hit the pistons leaving heavy imprints. The exhaust valves have the HD springs for e-brake. One gear case bolt was in the pan. The one that fell out was the one near the oil pump. I didn't see any damage from this other then the bolt was chewed up some. The question is what caused the piston/valve contact on only the exhaust valves. It seems like if they floated all the valves would be affected.



The truck has seen many owners and is turned up. It pulls loads and is not well taken care of and has over 200k I think but could be wrong as it might be under 200. I did an HG (external leak near t-stat) on it last summer and adjusted the valves a few months later with no problems and it ran fine for some time.



Ok, that's pretty much the info on the truck. My thoughts are over rev on a down grade with load maybe but then why just the exhaust valves with HD springs? I don't see how the fallen case bolt could have caused this. Could the cam key have sheared somehow and retarted the cam? Could that bolt have shocked the gear train some way and caused the cam gear to move? The cam has not been pulled or engine turned to check timing. I'm just looking for ideas as to what could have caused this.

 

[Fordiesel69]

You will need to check gear timing. The bolt could have broken the gear and therefore when the cam stopped, the piston slammed the valves that were left open. Looking at the gear train will tell the tale.

 

[CumminsPower98]

The cover is off and there is no visible damage to any gears. The strange thing is that there was heavy contact between all pistons and exhaust valves, which makes it look like the cam was lagging while it was running. For now its just sitting and they will probably just get a used engine so I won't be messing with it. I just can't understand how the key could shear unless something bound the cam up at some point. Everything turns now that the junk is out of the cylinder.

 

[dseabaugh]

overheating to point exhaust valves siezed in guides? I've seen many red glowing manifolds over the years, not that I would ever do anything to cause that and mufflers so hot you could see the insides without boiling any water.

 

[DonFitzwater]

Chewed up bolt? Timing cover bolt I assume. If that's the case I would lay money down that's your problem. I just did a kdp fix and found several loose bolts on the front of the engine. Made the hair on the back of my neck stand up!

 

[hsmith]

No key on the p-pumps.

 

[DonFitzwater]

No key on the p-pumps.

Did I miss something? I see where someone was talking about cams but I'm not seeing the comment about the P-pumps?

 

[CumminsPower98]

Correct, there is no pump key. I'm questioning cam timing and this is keyed as far as I know. The bolt that fell out is the bottom inside gear case bolt just above the oil pump and crank. I too am questioning whether or not this caused the problem some how but just can't see how it could change cam timing. I wish I had the engine where I could play with it but I don't so I'm just speculating. I didn't see any damaged gear teeth either.

 

[SRath]

It really sounds like it jumped timing somehow. Or froze up the valvetrain momentarily when the bolt got caught in a gear. But you would expect some gear damage somewhere if that were it.



Sounds kind of crazy, but could it have actually broken the cam and now the two pieces are kind of mated back up and turning together again?

 

[hsmith]

Thought he was talking about the pump shaft, but really asking about the cam. My mistake.

 

[Lurch]

Since it is just exhaust valves wouldn't an over rev with exhaust brake on make more sense?