88 4.0 valve train rattle

[krusty2]

At about 3000rpm I start to get a rattle that I swear is in the top end of this thing. I have chaged the lifters, pushrods and rockers and still have the same problem...When I had the head off it was full of carbon so I was confident that by a good cleaning and the parts I was replacing , I had it fixed......ummmm...no..... Any ideas as to what I am missing here??
Thanks..

[The Machinist]

Are the push rods tight after you torque down the rocker arms?  Do you have low oil pressure?  If you have low oil pressure your lifters might not be priming up.  Lifters need a minimum oil pressure to be pumped up enough to close the gap to the valve stem.  If you have good oil pressure you could have a plugged oil journal.  What type of oil are you using?  Try running a synthetic 5w30, sometimes that will help lifter noise go away.

[krusty2]

Push rods are tight....30lbs pressure at 3000, does this motor need more than the typical 10lbs per 1000 rpm?? Could I possibly have the pivots in wrong?? I am running castrol syntec with a bit of Lucas in it as well...When I had the head off I really went over the springs and stuff looking for damage but it all looked really good. Which journals are you talking about. the 2 in the head itself??
Thanks for the info..

[The Machinist]

     The journal I was referring to is the one in the block that feeds oil to the lifters.  Normal oil pressures in the Jeep 4.0 engine when the engine's hot are minimum 13psi at idle, and minimum 37psi from 1600rpm upwards (10W-30 weight oil).  If yours is less than this running a 5w30 synthetic will not work because you will have a lower oil pressure with a thinner oil.  A cheap fix for this might be to replace your oil pump with a high volume pump.  Melling makes a good one that puts out an additional 20% volume.  Low oil pressure is typically caused by excessive wear in the engine bearings, too much clearance.  The best fix is a rebuild, but replacing the pump to a high volume pump should help with the noisy lifters and help your engine last as long as possible.
Melling - M167HVS  If you decide to go this route I can check a price on a pump for you.  Hope this helps.

[krusty2]

Thanks for the help, It may just be that the pressure is too low.I will see if i can find one today, otherwise I will let you know...
Thanks again...

[hps4evr]

i actually had a valve cover go on slightly crooked and it was rubbing one of the rockers. odds are that it aint this but something to watch for when installing the valve cover.

[krusty2]

Thanks to the machinist and double checking the oil pressure......changed to conventional oil and 1/2 a bottle of lucas heavy duty....pressure went up and the niose went down...New hv pump and thicker oil and we should be good for a bit..

thanks again to all that have helped.