When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
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.
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Originally Posted by Dave51
Guess we're gonna find out!
OP in this case said "My '93 XJ has an '89 Renix head on an '01 HO short block." And I believe a new cam. So, no question he should set preload.
Also, preload is set at the factory and they often used different length pushrods to do it. Sometimes the different ones are clearly marked with a colored band. My guess, sometimes not.
But, with his symptoms, I have my doubts that is all of his problem. Sounds more like head problem..
OP in this case said "My '93 XJ has an '89 Renix head on an '01 HO short block." And I believe a new cam. So, no question he should set preload.
Certainly agree he should check.
However, I'm going to bet a buck it will be normal. I did qualify my question:
Originally Posted by Dave51
If the OP didn't shave his head, and if all the parts are stock and undamaged...
so that would exclude weird cams and fat head gaskets (altho it seems to me that a fat gasket wouldn't create his issue).
But TTBOMK the 4.0 has always used the same push rod (3300 2986) so no matter what he mixed up, as long as the parts were within spec they should work.
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Originally Posted by Dave51
Certainly agree he should check.
However, I'm going to bet a buck it will be normal. I did qualify my question:
so that would exclude weird cams and fat head gaskets (altho it seems to me that a fat gasket wouldn't create his issue).
But TTBOMK the 4.0 has always used the same push rod (3300 2986) so no matter what he mixed up, as long as the parts were within spec they should work.
Another fun thread.
Well, no they didn't at all use the same pushrod, as I tried to explain earlier. Which might be one reason the fsm says to keep them in exact order. They mixed them up as needed to adjust the preload because that's the whole point, they may not all be the same. Wherein you might see a particular cylinder with both having a colored band, and none on any others, denoting a different length of rod from the mopar factory..
A fat gasket will certainly throw the preload out to about .100 but yeah might not be his um only issue.
Last edited by 97grand4.0; 02-06-2020 at 05:15 PM.
I'd like to inject something here. If the valves were reground and reseated, the whole geometry could have changed. Sinking the valves deeper into the head will cause more preload on the lifter unless the valve stems were dressed to compensate.
There is a lot more to rebuilding an engine than a lot of people realize. Although the Chevy small block could be thrown together with mismatched parts and still run strong.
97Grand4.0, your referenced post about valve preload should be a sticky. It is well done and you used CCKen's picture perfectly! Zero lash and 3/4 turn is the true sweet spot at .042".
I seem to remember that's the same for sbc as well, although the bolt thread is different. 3/8-24 instead of 5/16-24. The thread lead is the same.
Engine: 4.0, new lifters valve job with new springs and exhaust valves, preload set with shims
Originally Posted by dave1123
I'd like to inject something here. If the valves were reground and reseated, the whole geometry could have changed. Sinking the valves deeper into the head will cause more preload on the lifter unless the valve stems were dressed to compensate.
There is a lot more to rebuilding an engine than a lot of people realize. Although the Chevy small block could be thrown together with mismatched parts and still run strong.
97Grand4.0, your referenced post about valve preload should be a sticky. It is well done and you used CCKen's picture perfectly! Zero lash and 3/4 turn is the true sweet spot at .042".
I seem to remember that's the same for sbc as well, although the bolt thread is different. 3/8-24 instead of 5/16-24. The thread lead is the same.
Thanks, Dave, I thought so too after I re read it! Are you nominating it?
As far as the valve heights, that is something the machine shop should be checking afterwards and grindig the stems so they all are the same installed height, obviously. I was able to lay a straight edge on mine ..very level indeed. But that is a quick check you should do too so right on.
I will add, that getting preload exactly at .040, in the real world probably won't happen with shims. I believe the spec range, to be acceptable anywhere therein, but, you would certainly want to try to aim for the middle at .040.
Last edited by 97grand4.0; 02-07-2020 at 06:29 AM.
Or just take ccKen's original post (cause his images are bigger for us visually-challenged folks):
Originally Posted by CCKen
You will be checking preload as you torque down the cap screws.
Crane has two procedures. The one I prefer is the cap screw turn method (1/2 to 1 turn).
The desired preload is between .020" and .060"
See pic below.
You'll install the bridge, pivots, rockers, and cap screws over the push rods. Slowly turn each push rod while slowly turning down the cap screws until resistance is felt in the push rod turning.
Mark the cap screw with index marks as shown in the pic. Alternate tightening the cap screws until they bottom out, then torque them to 21 ft/lbs. Observe the index mark position. This will show you the preload on the lifters.
02-06-2020, 03:45 PM
