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Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
didn't have the chance to do a compression check today, because I loaned my tester to my buddy at work, but I'll check it tomorrow, but however I did manage to reset the PCM and do the distributor mod and get the rotor where it's actually supposed to be and it ran a little better. Still has a rough idle but I've ordered new plugs, cap, rotor and coil from summit just to be sure. Also gonna change out the crank position sensor since it has 341,000 miles on it.
I have a push rod checker that's not the issue, if it was then I wouldn't have compression in any of my cylinders since they are all the same length. Plus with the cylinder at TDC I can twist the push rods and they have a good drag on them.
Okay, with the leak down tester on cylinder #6 and it a TDC I can hear the air escaping, and since I have the valve cover off I loosened one rocker at a time to see if it got quieter, no change reinstalled them. My leakage is rings and it's in an exceptable range, so I threw the compression gauge back on it for fun and now I'm reading 180 WTF!!!
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Not to say you aren't on to something with #6, but reading the changes you made, you would certainly be busting lifters if you did not set the preload first, either with a micrometer and push-rod checker , or by the rocker nut turns and rocker pedestal- shim method.
Are you oiling all your lifters, or, you were oiling then a couple stopped? Sure signs.
Regardless you can not skip this absolute critical step if you change ANY thing in the head, gasket, lifters, etc. or you will not run right and if it runs it wont for long.
Changing a cam to a non stock, this is Mandatory! goodness.
Last edited by 97grand4.0; Jan 27, 2024 at 11:54 AM.
Not to say you aren't on to something with #6, but reading the changes you made, you would certainly be busting lifters if you did not set the preload first, either with a micrometer and push-rod checker , or by the rocker nut turns and rocker pedestal- shim method.
Are you oiling all your lifters, or, you were oiling then a couple stopped? Sure signs.
Regardless you can not skip this absolute critical step if you change ANY thing in the head, gasket, lifters, etc. or you will not run right and if it runs it wont for long.
Changing a cam to a non stock, this is Mandatory! goodness.
Preload is good I can literally turn the push rods between my fingers at TDC. Also when i did this I told comp cams and edelbrock exactly what I was doing and what head gasket I was using and they told me the factory setup is fine.
At the beginning of this thread, seeing the immediate problem... I was wondering how that cam and heads were going to play out being used on a high mileage bottom end...I've never seen anyone use the comp extreme cam in this situation with the specs of the cam.. Time to freshen up the bottom end to match the top end...
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Originally Posted by J/D/S
Preload is good I can literally turn the push rods between my fingers at TDC. Also when i did this I told comp cams and edelbrock exactly what I was doing and what head gasket I was using and they told me the factory setup is fine.
ok, Lets be honest here, do you KNOW how to check preload? Y / N.
Because turning the pr with your fingers is not the way.
Did you see Dave's post #21 and go to that link? The pushrod is supposed to ride in the middle of the lifter plunger travel. That little tiny space inside the lifter that the spec calls for is thinner than a US dime. You changed everything from the cam to the head!
Yes is will all work, IF you have the right preload. But its not the first time I heard of a cam salesman completely not mentioning preload.
I suspect your bigger ( or even a new stock) cam is holding valves open. And it will continue to do so until you check preload. Also it will munch lifters. And valve stems, and cam lobes.
just my 2c
Last edited by 97grand4.0; Jan 27, 2024 at 01:12 PM.