I'm looking for suggestions on how my #4 exhaust valve and piston came in contact with one another. The 4.0l 266k miles has had a slight ticking noise for some time that I believed to be lifter tick. Last week it started running real rough at highway speed she heated up real quick but I managed to get home without ever exceeding normal operating temp of about 210. I found cylinder #4 to have no compression and missing coolant so I assumed it was head gasket. After getting the intake and exhaust manifold off I found the rear half of the block to be wet. So I pulled the head last night and also found bent #4 exhaust valve and a clear mark on the piston top.

I baby this thing because of the amount of miles and just needing it to get me by as my DD so I don't rev it hard enough that valve float should be an issue IMO. Being a non interference motor I would think timing is not the issue either. I did have some overheating issues a year or so ago but I'm not sure if the noise corresponded with any of that. I've never received any misfire codes until this latest episode. It doesn't look good but not terribly bent either. I guess what I'm asking is do you think the valve has been like that for awhile or did the valve and gasket damage happen at the same time?

I don't want to just replace the valve and piston only to have this same problem. What else could cause this interference?

 

Valve seized in the guide.

 

I thought the 4.0 was a non interference motor.

 

That's what I've read which means the valve and piston should never occupy the same space at any time. The valve could stick open at max lift and still never come in contact with the piston.

 

 

I guess I need to pull another valve to see that it fits snugly in the guide and didn't get off centered, it did just catch the edge of the relief. If it's not that then maybe some foreign object got caught between the valve and seat? Idk if that could bend her or not

 

 

pushrod is straight, no abnormal coloring on the stem, or marks on spring, or rocker. Spring same height as the #3 I pulled tonight. Retainer and stem groves are good

 

Chunk of carbon got between valve and piston most likely.

 

Im going with blown head gasket, or crack in the head, which then overheated exhaust valve that bent and stuck.

 

Whats that notch from in the edge of the piston at 6 o'clock?

 

forward (towards front of block)

 

Warped space from a gravity wave caused by two distant black holes colliding? or maybe carbon.

At 270K, me, I just might. Ridge ream and hone all, in the Jeep. Hand, (with drill) lap the valves, assemble with new rings and rod inserts. That didn't use to cost much and you just might see another 270K. Just a thought, don't know your situation, I've done it with good results on a couple of other engines.