I'm in the middle of replacing a cracked 0331 on my 2000 XJ. First time diving into an engine this deep so I'm looking for some guidance. Just cleaned up the rockers to inspect them and have a few q's for you good folks!

First, the wear on one set of pivots is significantly narrower than on the others (see 1st pic). Is this normal or anything to worry about?

Second, the top of the bolt hole on one of the bridges has a large gouge (see 2nd & 3rd pics); large enough that the bolt wouldn't actually slip out and instead had to be threaded out. What would cause this? I don't recall any of the bolts feeling over-torqued when I removed them.

I'm not opposed to replacing the rockers/pivots/pushrods, but want to make sure there isn't an underlying issue (lifters?) before I go buttoning everything back up.

Thanks in advance for any help!



Notice the wear marks on the center set of fulcrums compared to those on either side.

"Gouged" bolt hole is on left, good one on right for comparison. Better angle of the "gouge" in the next pic.

Better angle showing the depth of the "gouge".

 

I'm not going to say don't replace them, but if they weren't making noise before then I wouldn't waste my time. They don't look scored or anything, they just seem like they're polished from use. And I wouldn't say there's any underlying issue either. And that rocker bridge may have been replaced with an aftermarket one at some time. Who knows... and again, I wouldn't worry.

 

You can replace them, not too expensive. Do any replacing of pivots rockers pushrods you want to BUT and this is the key to the entire job you are doing right now if you don't want complete disaster. YOU MUST CHECK THE PRELOAD AND ADJUST WITH SHIM WASHERS OR CUSTOM PUSHRODS.

You don't need fancy tools, you can use the Count the Turns method. Do not start this engine unless you have read, understood, and checked the preload.
This is 100% mandatory for these engines or any other with so called non adjustable lifters, if you don't want to munch parts by having no oil.
On the other hand, once you know how, and it's really not hard, you can change out any parts you like with complete confidence including a different head and head gasket.
Once you take a head off and mill it or change it or change the valves or machine them or change any valve train parts, you alter the preload. You must set it or you will munch a lifter and then all the oil will shoot out it and the others will be dry all the way up.
Also having it set correctly will ensure you have proper engine vacuum.
Check each one. ! Once you get this down you can do anything, ..change cams etc.

 

I very much appreciate the responses. Regarding the count the turns method, I've found some slightly conflicting instructions regarding where you mark zero lash. In this post by Dave1123, it says to tighten the bolt until you can't turn the pushrod. However, in this post by CCKen, it says to tighten just until resistance is felt. With the caveat that I haven't actually set the preload before, it seems like there would be enough difference between the two methods to have one or the other end up out of spec. Can anyone clarify which method I should be using?

 

https://cdn.xjjeeps.com/pdf/en-us/20...ice-manual.pdf

The answers you seek shall be revealed

 

Yeah, I have the FSM. I even printed out all of Group 9 for the 4.0. However, the FSM gives no guidance regarding preload--see 9-96 to 9-97. If the information I am "seeking" is located elsewhere, would you be so kind as to point me to it within the nearly 2000 pages of the FSM?

 

Correct. The FSM tells zero on the whole process. Go figure. 1200 pages and zipo.
CCKen was the OP of that chart, I lean heavily to his guidance. When I have done this, simply tightened to where the pushrod is seated and resistance is felt. Zero up down play is what you want. Any much more and you might be compressing the lifter. You'll know. Pretty easy to discern when you're there.

 

By the way Competition Cams sells the shim washers and instructions specific to the 4.0 jeep.

 

FSM does have good info on torque sequence and which bolt gets the sealer applied ..I think it was loctite, to prevent coolant leakage . Also Id replace the head bolts

 

Hey sorry to butt in...97grand4.0......can you go back and do the lifter adjustment you described on a stroker that already has 30K on it since rebuild. I just bolted everything in way back when. My valvetrain is not the quietest thing around..thanks Its a 98

 

Absolutely you can. And should. When misadjusted they might be fine for quite a while, then one day you pull the VC and boom, one is squirting to the moon and the others are dry. What happened to me. .020 to .060 is the spec, so thats only 40 thousandths. Less than the thickness of a US Dime. So yeah, they're fussy. By the way, alot of people say to get it dialed in right in the middle, in my opinion this isn't necessary.
Another note, when first firing up, FSM and I say do not operate above an idle, until you see all are oiling.

 

With the VC off it will idle pretty high due to lack of vacuum (I think?). Is that alright? I'm not sure how I would be able to check that they're all oiling with the VC on, but I'm a novice and would rather ask a silly question than make a silly mistake!

Thanks again for all the help, 97. Can't say that enough!

 

No, not if you plug the vacuum ports on the intake first. Only 1 to the CCV, If you miss something and it races up just shut it off immediately.

 

Damn I was sure the FSM had the procedure in it.

In theory, you shouldn't have to adjust the preload.... in theory... but not reality.

 

Why in your theory should one not have to adjust preload. One should not have to go to work to earn a living either but it's the sad reality. One should not have to things that are difficult and hard to understand either. Others do it because it IS difficult.