2000 cherokee sport
4.0 liter, automatic 4x4


Just did a major repair. Had a collapsed lifter eat a cam lobe, so I replaced the cam with a melling oe grind cam, replaced the lifters with melling factory replacement, took the head and had a valve job done, replaced the timing set with cloyes replacement, followed the procedure to reinstall the cam sensor and synchronizer. Engine runs smooth and quiet just does not have the power it did before, no new codes.feels like I'm towing a trailer or fighting a 30 mph headwind. Any ideas, I thought I had the timing off but I dont. Can you rotate the cam synchronizer to adjust timing (don't think so but worth the ask). Help any ideas please, my scanner is limited.

 

Did you check the preload on the lifters?

https://www.cherokeeforum.com/f2/new...stment-213117/

The CKS and CPS may be out of sync:



https://www.jeepforum.com/forum/f19/...e-fix-3487474/

 

I haven't ever done the preload in a 4.0 before, usually just torque and go. I can look at it. I have a feeling it is probably going to be a correlation issue. I didnt know if you could rotate the body of the cam synchronizer shaft or not ornif you should but it makes sense you use it to fine tune like a distributor. I dont have a scope tool though, might wing it, see what happens.

 

Well, FYI this is what a properly synced CPS looks like on the oscilloscope:

 

If you dont have a fancy scope like Dave, you can run a quick compression test. If its low, then there is a good chance the cam timing is off. But ya, also check the preload. If you have too much, that will do it too.

 

You know, I think you could sync them if you had 2 multimeters. Hook the multimeters up to the cam and crank signals, turn the engine over by hand, and observe that each group of 4 crank signals is entirely within a 0.0 or a 5.0 volt cam signal, then it would be OK.

Now admittedly, I just invented that, so take it with a crate of salt.

 

SO. New cam lifters, the whole 9 and you did not set the preload (valve lash) ? No way. You have to. Quick, or you'll be tearing it down again. Could also very well be your performance issue, if you don’t have the right preload your vacuum will be way off. Id bet this is what was wrong with the old engine too.

This is worse yet because you just dumped a ton of money on great parts that you dont want to munch.

The preload spec is a range less than the thickness of a US dime on these engines. .040 I believe. Anything changes the geometry like new parts, let alone new cam, lifters etc, and you are outside that range and lifters get munched and spurt all the oiling out one lifter. Might not even make noise but one day you pull the cover and find no oil to all your lifters but one. Let alone that you are getting low vacuum.

 

 

Where did you find this? Adjusting non-adjustable rocker arms? I've never seen anything like this. If you have less than 21 LB FT on those bolts, they're gonna spin out and you'll have a mess. Preload on the lifters is determined by the length of the push rods. So if the OP had his head resurfaced and the machine shop took .0XX" off of the head, he would need push rods shorter by .0XX". Head gasket thickness will effect lifter preload as well. You can measure the preload with a dial indicator or the straight edge & feeler gauge method. .030"-.040" is what you should be targeting but the acceptable range is .020"-.060"

Watch this video, @ 3:13 this guy measures his push rods

 

" If you have less than 21 LB FT on those bolts, they're gonna spin out and you'll have a mess."

True. If you read the diagram it says to measure at 21 ft. lbs.
This is how you adjust by using shim washers between the pedestal and the rocker pivots. You can also adjust with a micrometer as you say.
Personally I have tried both methods. Unless the mill is on an engine stand, IMO you are far better off with the turns method described above, which was originally posted by CCKen.
You can look him up on here, I think he was aircraft mechanic.
That they aren’t adjustable is urban myth. You wouldn’t dream of putting a chevy together with new cam and lifters without adjusting them.
Same thing here.
Just nobody knows how so they don't do it. With disastrous results.

By the way, the last guy I helped through this process was also built himself a 'stroker'. Never heard of adjusting these lifters either. Blew a brand new lifter and had to tear it down again before he got it off the engine stand.

 

I gotchya. He just converted the preload to torque to angle like they do with LS Engines. Actually pretty clever. I have a head swap coming up so I'll maybe use this to verify the measurement I get.

 

Actually he didn't do it, the method has been around a long time. Since the pitch of the threads is known, it works out great, and from my measurements is as about accurate as a human is going to get on an installed engine. Try it? You'll like it.

I learned the hard way, it's documented on here. I did lifters and a valve job, 4 months later pulled the VC.
One lifter was gushing, the other valves weren't pumping at all.