97grand4.0

The wear pattern on the end of the stem, together with the 60 lb compression, and the bent plug, tells me that valve is hanging open. Its hard to dismiss that wear pattern.
Hard to know which came first the chicken or the egg, maybe the valve got burnt, then bent. I think you said exhaust valve right? Exhausts are the most common to burn of course. Also you were on a long drive, maybe a long uphill aggravated it to where it overheated and stuck. And where it would act up most is at idle. Cant ignore that compression or the bent plug either. Hanging open a hair or two I think but not sure that would hit the plug. Which would itself bend the valve.

Another observation is the lifter oiling channel flows from the pump up to the center lifters , outward, so it makes it to the #1 and 6 lifters last. However a problem of this sort I am somewhat less suspicious of because your rockers all seem to have a uniform healthy amount of oil on them. I have seen that exact pattern on a #1 stem on my own jeep when the lifter preload was too tight. Therefore I lean toward a valve sticking. You can clearly see it wasn't rotating and starting to catch some serious wear. Either way I see a valve job in your future.
Hope this helps let us know.

dave1123

Remove both rockers on #1 and measure the spring height. If the valve is hanging open or the head is warped, it should be obvious with a short spring height or weak/broken spring.

indyhoya

Thanks to all for the input and suggestions. I performed the valve rotation as stated in the service bulletin which fixed the compression in Cylinder 1 (155 psi). On a test drive I still had all sorts of misfire issues, pulled the plugs and had a significant bend and only a tiny gap left in the plug in Cylinder 4, no bend in Cylinder 1. I am sure all of the plugs had gone back in their respective cylinder and not an issue of mixing up 1 with 4. In both cases no evidence of a mark on the electrode that would indicate something hitting it. With the compression up to normal I started looking back at electrical and noticed by unbolting the rail and inserting the plugs that there was a significant difference in strength of spark for Cylinder 1. I replaced the rail, bought 6 new plugs for piece of mind in case the last new batch I got had some defects.

Upon installing the new rail I noticed that I had forgotten to reconnect the ground from the engine head bolt to the firewall that I had taken off to remove the valve cover which was probably another contributor to my issues on the test drive. Anyways-with that properly connected, the new plugs, rail + previous valve rotation engine is running great again at idle, low speeds, high speeds on freeway, no check engine or other miscues yet. Still puzzled on what could explain the spark plug gap closing in multiple cylinders, will keep an eye on things but hoping the issue is resolved!

Dave51

Thanks for the follow-up!