Wcreech8

Backstory:
1993 Jeep Cherokee XJ. The PO blew 6th cylinder piston so I pieced together an engine and mismatched the engine parts (i.e. 1993 intake on Renix head, the Renix head on 01 block). Posted a thread a few months ago about the engine running rough and rich. I learned about the differences between heads and intakes throughout the years and realized my mistakes. Thread can be found here: https://www.cherokeeforum.com/f2/val...-4-0-a-255728/
I had the original head (1993 Casting #7120) rebuilt which I'm putting on tomorrow along with the 1993 intake. I bought new lifters because might as well while I have the head off. I also bought new rocker arm pivots because the previous pivots had wear. The push-rods look fine, no scarring on the ends and are clean throughout. The rocker arms also look fine, no abnormal scarring.

My questions:
1) In my previous thread a user had suggested to check the pre-load on the push rods to ensure desired clearance of .020"-060". But how do I go about this? Also why would I do this procedure because the valve train isn't adjustable?
2) I understand I need to apply assembly lubricate to the bottom of the lifter where it meets the camshaft but do I need to apply lubricant or oil to the sides and tops?
3) What would be the best way to prime the engine before initial start up?

I appreciate anyone who participates in this thread and is willing to provide valuable advice. Thank you

dave1123

This should be done for each piston in the firing order sequence by turning the crankshaft 120* each time.

Any time work is done on a head either reseating valves or planing the head surface or swapping different heads, this should be checked. Even a different thickness gasket can change the preload. You can spin the oil pump with an electric drill down thru the distributor hole before you put the cam sensor in. Be sure to index the cam sensor drive correctly.

Wcreech8

So I got the head back on. Also replaced the lifters and rocker arm pivots. Still have some confusion about checking the preload though. I got cylinder 1 on TDC Compression. I alternately hand tightened the rocker bolts while twisting the push rods. When I felt resistance on the push rods I indexed the bolt and pivot. Torqued the rocker bolts to 21 ft. lbs. from zero lash and came up with ~1.70 turns. This seems excessive so I just want to be certain about this process before moving forward with the rest of the valve-train. You start at zero lash and torque to 21 ft. lbs. while keeping track of the index. And from zero lash there is going to optimally be anywhere from 3/8 of a turn to 1 full turn to reach 21 ft. lbs based on the diagram?

I really do appreciate the advice and guidance. I’ve gone through this headache before and would like to get it right this time around. If there’s any other questions feel free to ask. Thanks again!

dave1123

You see? This is where is gets dicey. Are you sure it's on the compression stroke? If so, that many turns is opening the valve. IDK if the 7120 head is any shorter in stack height than an HO head, but over 1 complete turn is bottoming the lifter plunger and opening the valve. With #1 the way it is, try adding a little air pressure thru the spark plug hole and see if the valves are closed or open. The optimal setting you want is 3/4 turn. I hope you don't need custom pushrods, but my not being there, it's hard to tell what's going on. With no rockers on and just the pushrods installed, mark the pushrods of number 1 with a Flair pen, then turn the crank and see if they go down or come up. At TDC compression, they should remain motionless for at least 45* before and after TDC. If not, you're on the exhaust stroke. Add a little preload to the pushrod with your finger to make sure it follows the lifter without any spring pushing it down.

I'm glad you had the intelligence to stop and check when you had a problem. Jeep manuals never mention valve lash because with stock parts, everything should fit together without worrying about it. In talking to my machine shop, he tells me when he grinds valve seats and faces, he has to grind the stems to match assembled height. The 4.0 is a great engine, but without adjustable valve lash, it can become a nightmare to do any major work on them if you're not aware of this. When I put a new Clearwater head on my WJ, the valve lash was perfect. After reconditioning that same head and putting in on a rebuilt shortblock, again the valve lash was perfect. It just shows professionals know what they are doing....for the most part!

QUESTION! What did you do about the head locator dowels? As far as I know the 01 block has them, but the Renix head doesn't have the holes for them. I'm pretty sure the 7120 doesn't either.

Wcreech8

I’ll double check everything and report back with pictures for more detail. BUT I thought that the Compression stroke was when both valves were closed and the piston was TDC. So I was turning the crank from the top with a ratchet and 3/4 socket. As I was doing this I was looking at both the push rods (to see when both valves were closed) and the spark plug hole for when the piston was at the top. After studying I believe I had the cylinder on the power stroke. All this is pretty new to me but I’m doing my best to wrap my head around it.
Honestly I don’t remember seeing any locator dowels. My head gasket fit right on the block. Then I used my dads overhead winch to slowly put the head back on. Everything fits flush. If there were locator dowels would they pose any problem?
Again I’m new at understanding the basics. It’s easy to bolt things on and off but thoroughly understanding how everything works is like learning a new subject for me

dave1123

It's possible the heads you were using have no metal where the dowels are located, but I know my 2000 0331 head and block had them. They should be in the rear right corner and the left front corner. If they are there, the gasket will locate on them as well as the head. It's entirely possible someone pulled them out.

Wcreech8

Got everything back together and made sure the preload was within range. Took the distributor out and primed the oil pump with a drill. Started it up and after tweaking with the timing it runs well. No more lifter noise and no more sporadic miss. After 3+ years I'm finally able to drive it confidently. Thank you for all your help and contribution. I'll make a thread soon about the restoration and make sure to mention your help.

dave1123

Good to hear! It's truly amazing that this engine is so bulletproof even with the lack of adjustable valve lash. Those rockers can rattle like a tin can full of marbles and it still runs! Here's something you may find amusing, my new rebuilt engine with a reconditioned Clearwater head and all new lifters, rockers, pivots, and pushrods is quiet on cold startup, but as it reaches temp, it'll rattle just enough to **** me off! If I've just come off the highway, it's quiet until I shut it off and restart it. Why?