Valve Issues with 4.0
02-05-2020, 06:32 PM
#1
Junior Member
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Join Date: Jul 2016
Location: Snow Hill, NC
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Valve Issues with 4.0
My '93 XJ has an '89 Renix head on an '01 HO short block. The engine has always ran rough at idle, misfired, and ran rich. I performed the paper test (stick a dollar bill over the tail pipe) and the paper was indeed getting sucked into the exhaust pipe. I'm planning on getting the head rebuilt, but I made the mistake of keeping my stock '93 intake, exhaust, and flywheel when I put the engine together the first time. Is it possible that this mistake is contributing to the issues I'm having?
Also, are all the gasket kits interchangeable throughout the years?
Would greatly appreciate any help,
WC
Also, are all the gasket kits interchangeable throughout the years?
Would greatly appreciate any help,
WC
02-05-2020, 07:42 PM
#3
Old fart with a wrench
When you put it together do you check the valve lifter preload to make sure it was right? It's possible you have some burnt exhaust valves if it was too tight.
Last edited by dave1123; 02-05-2020 at 07:50 PM.
02-06-2020, 08:34 AM
#4
CF Veteran
Any codes? Hows the fuel pressure? Compression test?
02-06-2020, 08:53 AM
#5
CF Veteran
02-06-2020, 12:00 PM
#6
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Join Date: Jul 2016
Location: Snow Hill, NC
Posts: 63
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Year: 1993
Model: Cherokee
Engine: 4.0 HO
Planning on doing a compression test tomorrow, I'll report back with readings.
I did not check the valve lifter preload, I honestly didn't know. I just dropped the lifters and pushrods in when I replaced camshaft. How would I go about doing this?
No codes and good fuel pressure.
Currently my XJ has the '93 stock intake, exhaust, and flywheel along with the Renix head. I should've kept '89 intake on the renix head but did not know prior to installation.
I did not check the valve lifter preload, I honestly didn't know. I just dropped the lifters and pushrods in when I replaced camshaft. How would I go about doing this?
No codes and good fuel pressure.
Currently my XJ has the '93 stock intake, exhaust, and flywheel along with the Renix head. I should've kept '89 intake on the renix head but did not know prior to installation.
02-06-2020, 01:07 PM
#7
CF Veteran
Planning on doing a compression test tomorrow, I'll report back with readings.
I did not check the valve lifter preload, I honestly didn't know. I just dropped the lifters and pushrods in when I replaced camshaft. How would I go about doing this?
No codes and good fuel pressure.
Currently my XJ has the '93 stock intake, exhaust, and flywheel along with the Renix head. I should've kept '89 intake on the renix head but did not know prior to installation.
I did not check the valve lifter preload, I honestly didn't know. I just dropped the lifters and pushrods in when I replaced camshaft. How would I go about doing this?
No codes and good fuel pressure.
Currently my XJ has the '93 stock intake, exhaust, and flywheel along with the Renix head. I should've kept '89 intake on the renix head but did not know prior to installation.
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02-06-2020, 03:12 PM
#9
CF Veteran
Fast and Easy Way to Check Hydraulic Lifter Preload when using Non-Adjustable Rocker Arms
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020" to .060" apart you have proper lifter preload. If the lines are the same or less than .020" apart you have no, or insufficient, preload. If the lines are further apart than .060", you have excessive lifter preload.
With the cam, hydraulic lifters and pushrods in place, install your rocker arm assembly. Use the prescribed method in your repair manual and torque down all the valve train bolts in the proper sequence. Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder. (At this position the valve springs are at their least amount of tension making the job a little easier to do.)
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now carefully remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020" to .060" apart you have proper lifter preload. If the lines are the same or less than .020" apart you have no, or insufficient, preload. If the lines are further apart than .060", you have excessive lifter preload.
With both valves closed and no load on the pushrod, you bolt down the rocker until zero-lash, that is no vertical movement on the pushrod and it still spins freely. ... set dial indicator to zero. Then you torque the rocker to the proper value and ... read your dial indicator. You need to be between 0.020 and 0.060". Ideally, something close to 0.025"- 0.030".
https://www.jeepstrokers.com/forum/v...=1561&start=45
Last edited by Dave51; 02-06-2020 at 03:15 PM.
02-06-2020, 03:17 PM
#10
CF Veteran
Here is where I gave the instructions a few days ago to another mechanic
https://www.cherokeeforum.com/f67/3-...ng-oil-255577/
https://www.cherokeeforum.com/f67/3-...ng-oil-255577/
02-06-2020, 03:21 PM
#11
CF Veteran
02-06-2020, 03:27 PM
#12
CF Veteran
If you're out of range you need different pushrods or shim the rockers if its too tight.
But now I have a question.
If the OP didn't shave his head, and if all the parts are stock and undamaged, what's really the chances of him having a screwy preload?
But now I have a question.
If the OP didn't shave his head, and if all the parts are stock and undamaged, what's really the chances of him having a screwy preload?
02-06-2020, 03:32 PM
#13
CF Veteran
What's really the chance all parts are stock and undamaged after 100k +miles and how many owners, or that he used the same exact thickness head gasket? Or that all the bridges pivots pushrods and rockers are factory new? Whats the chances a head hasn't had a valve job or two, or that valves weren't cut, or that new seats cut or certain cam lobes worn unevenly. Zero.
02-06-2020, 03:42 PM
#14
CF Veteran
No that thread has the 2 methods. Only XJ_Corey is talking about lash and the other members get in a big fight and the thread gets locked.