Valve Issues with 4.0
#16
CF Veteran
#17
CF Veteran
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..
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..
#18
CF Veteran
However, I'm going to bet a buck it will be normal. I did qualify my question:
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.
#20
CF Veteran
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.
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.
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.
#21
CF Veteran
#22
Old fart with a wrench
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.
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.
Last edited by dave1123; 02-07-2020 at 12:14 AM.
#23
CF Veteran
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.
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.
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.
#24
CF Veteran
Or just take ccKen's original post (cause his images are bigger for us visually-challenged folks):
https://www.cherokeeforum.com/f2/new...stment-213117/
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.
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.
Last edited by Dave51; 02-07-2020 at 06:41 AM.
#25
CF Veteran
IDK why if you copy ccKen's image it shows up smaller than his original. Oh well...
Last edited by Dave51; 02-07-2020 at 06:44 AM.
#26
CF Veteran
Yeah either way Dave51, when you do yours for the first time you can let us know how it went too.
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