So my 98 xj has a cracked head and I'm buying a new one for 400$ can I reuse my pushrods and rockers if they are in good shape or do I HAVE to replace them?

 

Absolutely. You may need to check the preload (that's debatable, and usually brings spirited discussion) but we'll get ccKen's procedure out to you so you'll know what people are talking about.

 

BTW pushrods and rockers don't wear. Check the lifters instead.

 

The new head come assembled with valves and lifters

 

Then you In Like Flint!

 

Id keep the old lifters, My buddy had the cracked head, replaced it, and he decided why not replace the lifters while he was in there. He got maybe 50 miles on it before the jeep had problems, we checked compression, it was bad, then we cranked it over with the valve cover removed, some of the rockers were barely moving. We pulled the new lifters and found them all horrible worn, some worn all the way thru to the point they leaked and would not pump up! cam was also trashed, lobes ground down. In 50 miles it self destructed. So we had to replace the cam and new lifters. Now he is not dumb, he put break in grease on the new lifters, but still they wore out nearly instantly. We learned from several sources that new lifters on an old cam sometimes dont break in properly, Thus do NOT install new lifters unless you install a new cam with it. Sure it may work sometimes, but other times it is near instant death.

also if you do pull out you old lifters, say to inspect, be sure they go back into the same hole, dont mix them. again this is for wear, they are broken into each cam lobe, so dont mix them around.
Id put on the new head and NOT mess with new lifters.
Push rods should also go back in the same hole, same orientation, keep the up side up, down side down. sure pull them to check for straightness if you want. the push rods however can usually be replaced on the old lifter, no problem, but if the old ones are not bent, reuse them.

That is my experience, and talking to some good engine builders, they say new lifters on an old cam can sometime fail just as we experienced.

so deal with the head, but keep using the old lifters, put them back in the same hole if you do remove them.

good luck

 

Sounds like a preload problem.

 

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

 

I don't find that credible. Something else major had to be going on.

 

Why would an aftermarket or reman cylinder head come with lifters? You probably mean springs, correct?

You do not HAVE to replace them. You would replace them if they are damaged (meaning the pushrods are bent or rocker arms are bent). You would also replace the push rods with shorter push rods if the replacement cylinder head has had a significant amount of material removed from the sealing surface. In that case you could also install rocker shims. Both scenarios are very unlikely. Either way, it is always smart to measure the lifter preload when replacing a cylinder head. The link that Dave provided shows a method of measuring the preload via the turns of the bolt from zero lash to 21 ft#. I'll explain. The preload references the depth of the push rod inside of the lifter plunger. We are targeting between .020"-.060" with an ideal .042" of preload on that plunger. Zero lash is when the push rod begins it's descent into plunger so that is where we start. When you find zero lash, you mark the cap of the bolt and then torque it to 21 ft#. Record the number of 8th turns. The bolt is a 5/16-18 fastener, so it has 18 threads per inch which is .056" per thread. Each turn of the bolt from zero lash equals .056" of lifter preload. Or each 8th turn equals .007". This is only one method of measuring lifter preload however. You can take a simple measurement with a dial indicator as well.

 

the preload was set.

 

Sorry for the confusion the new head did not come with new lifters nor did I replace or mess with the lifters I ended up using the same rods and rockers she fired up and ran smooth no problems with great compression also just to let you guys know I only set #1 cylinder to TDC on compression stroke then torqued all rockers down instead of doing that for each cylinder made no difference

 

Makes more sense since the lifters ride in the block...I thought the CW was you can run new lifters on any cam old or new but you cant re-use old lifters on any cam, Except the cam they came from and it has to match exact position they came from