87 Cherokee, and I am still trying to get rid of the lifter click. I am trying everything before I pull the head. So, is there a reason why I cant or shouldnt pour Marvel Oil down the push rod tubes? A little bit each day for say a week, with out running the motor. Kinda let em soak. Then put a fresh change of say, 5w30 with some MMO in it, and see if that loosens em up?

How about pulling the pushrods while the rockers are out?
Make sure they're clear. Pour MMO directly down on the lifter?

Have you added a quart of MMO to the crankcase yet? How high do you ever rev your 4.0?

Lifter tic is not exactly the lifters making noise...its the valve face hitting the head seat because the lifter isnt quite fully pumped up. MMO in the oil works well but does not work instantly..it may take several weeks

This is what I had in mind. I guess I should have said " in the pushrod passage through the head and block" I didnt mean through the little oil hole in the push rod.

I have cleaned the push rod oil holes.

About 1000 miles of MMO in the oil.

I run the motor through all the RPM ranges. Sometimes I mash on it and rev it to its highest shift point, about 4000 rpm, and other times I just ease along.

I have been running 15w40 oil though. I will try maybe some 5w30? 15:40 probably a bit too "thick" now that I think of it.

5W30 in the summer is way too thin. I6's are never really quiet. You always know when they're running from 100 yards away

I had good luck with this stuff 20 years ago in a 2.9L Bronco II. Really helped the transmission as well.

https://auto-rx.com/

So I had the best engine guy I know, he is an absolute expert, look at my motor. We took the valve cover off after it was up to temp. Ran it, oils was flowing on in and around all the rockers. As soon as we heard the clack we shut it off. We found three rockers that were loose and one was really loose, like shake the oil off of it loose. He says its time to pull the head and change lifters. He will look at the lifters then to determine if the cam is chewed up💰💰💰

Did you check that the rockers were tight as in torqued properly?

Yep. The head is coming off. No question.

understood. Just making sure.

I do not wanna do it, but, it will be worth it, so long as the cam shaft is still good

If the cam is bad, it can be replaced with the engine in the Jeep.

yup. At that point you are half way there anyway.

And put a performance cam in.