97grand4.0

I think you answered your own question.

94CountryClub

It seems like I have opened a can of worms here - but I am learning so much.

I guess what I am learning is this adjustment is more of a check unless you have spacers or something to put on the rocker tower.
I got really confused at first calling it an adjustment because from all I could understand it seemed like I was not adjusting anything but rather confirming that my preload was within two values. If it wasn't, I wasn't going to be able to fix anything without some spacers or different push rods.

97grand4.0

I think adjustment is correct. When you "adjust" the lifters on your garden variety chevy engine, you are doing the exact same thing, setting where the pushrod rides inside the lifter.

I think what throws off so many people with the jeep engine is that indeed the fsm only instructs to torque them down and is totally silent on the whole preload adjustment. That is a bit of a mystery that I think has more to do with Chrysler selling new cars.

Randy Bobani

cruiser54

Torque the rockers. It ain't a Chevy!

97grand4.0

a few previous posts
https://www.cherokeeforum.com/f5/hel...xhaust-252112/
https://www.cherokeeforum.com/f2/how...h-rods-257311/
https://www.cherokeeforum.com/f67/fi...ockers-255570/
https://www.cherokeeforum.com/f2/val...-4-0-a-255728/

cruiser54

Just got off the phone with my local machine shop. He assured me that a simple head surface is not going to require shimming of the rockers or shorter pushrods.
High lift cams etc you might be prudent and do the measuring thing.

94CountryClub

An update to all.

First off the back and forth here really was useful - I saw a few different takes on what I should do and figured I would need to make up my mind somehow on what I should be doing. Thanks to everyone who threw advice my way. The Jeep would be totaled if not for this forum over the years.

figured if the lash check wasn't tough - why not check? I really wanted to know if I was out of the preload spec (even if I probably wasn't) - so I went for the check of my preload via the bolt turning / index mark / method. I bought rocker shims in case I needed them and had them in front of the Jeep with me in the event that I needed to use them.


What I did:
I put each cylinder at bottom circle so that both valve springs were relaxed / closed. Basically I put a 3/4" socket on the end of a breaker bar and moved the engine pulley until the cylinder I cared about (the one I was doing) had the valves chilled out and not depressed. Wasn't too bad.

With my push rods in place I then focused on the first cylinder. I cleaned up the rocker hardware, installed it by hand tightening the rocker tower bolts back and forth back and forth between the two valves of the cylinder I was working on. Once I got close to tight I took my fingers and started spinning back and forth the push rod and tightening the rocker tower bolt down at the same time. When the push rod wasn't as easy to rotate / stopped rotating - I would then stop tightening the bolt. This was considered zero lash to my understanding. I set the index mark at zero lash of the rocker bolt with a paint pen across the bolt and bridge (just when i could no longer spin a push rod / felt pressure on the push rod), and torqued to 21 ft/lbs

Then (with the bolt now at 21 ft/lbs) I looked at how much the bolt rotated from the zero lash (just tight enough to stop the push rod from spinning / pressure on push rod). When I finished one cylinder I moved to the next - just making sure that each time I changed cylinders I would rotate the engine to a point where the valves were not depressed / was on bottom circle. I worked straight backwards 1,2,3,4,5,6 for the cylinders. I am sure that when #1 cylinder was good that I could have jumped over to 5, and messed around like that - but it was easier for me to just go 1,2,3,4,5,6 and adjusting at each cylinder with the engine pulley for the valves. It really wasn't a big deal time wise.

Result:
All of the rockers were within spec and my average was about .028" (180deg or half a turn). Spec being .02 to .06.

I think that I might have considered "zero lash" a little tighter than a few others - so 3/4 of a turn (270 degrees) seems to be about right - the 3/4 of a turn being what others are saying is the ideal preload.

I guess that means the $20 I spent on the rocker tower shims was a waste but you can't know that at the time and I was glad to have them on standby in case one of my preload checks failed and I had to do something about it.

SO THAT'S GOOD NEWS! and I learned a lot! Again - all thanks to you guys!

I would say that that despite the polarizing opinions on the matter that you should check preload if you did something to the cylinder head - mainly because why not? It's super easy.
I suck at doing things in a timely fashion on the Jeep - I take forever - but even for me, with the rocker towers exposed anyways - why wouldn't you do the check to confirm all was OK?
I believe it's probably true that with a typical cylinder head gasket swap most of the time you will get away with just torqueing the rockers down - but - why not check? It was dead easy to do.

Safe to say that at least the resurfacing and valve job of my cylinder head did not throw the preload out of wack. Maybe if I used new push rods or other new components that could have changed something - I don't know - but I didn't and I kept the same push rods and rocker arms going back into the same place.

So thanks to all and I hope you know how much I appreciate you guys! Even when you don't agree with eachother because different takes on the same topic are so useful to compare and dig into.

THANKS! I owe you all beer if you come down to Houston