Ill get right to it, my original 4.0l motor went out around april of 2020, i purchased a brand new stock 4.0L longblock from a reputable company online and had it shipped to me, i had it installed by a company near me and they did the break in process with some regular 10w-30 oil that i provided (without me knowing about lack of zinc in regular oils), within about 2k miles after, the cam and lifter failed on it, i know because i removed them and the lobes were near flat and 2 of the lifter bottoms were mushroomed at the bottom, so they couldnt be pulled out with a magnet they had to be dropped down into the oil pan, i purchased a brand new melling camshaft aswell as a new set of melling lifters, as well as joe gibbs driven HBR 10w-40 break in oil, i used moly assembly grease oN the cam lobes as well as lifter bottoms, buttoned everything back up and the jeep fired right up no delay, i revved it inbetween 1500-2000 rpms for about 25 minutes then shut it off, drained the oil and changed the oil to joe GIbbs hr2 10w-30 oil and started driving it, it was good until about 3k miles then i noticed at low speeds when accelerating it would have this slight knocking noise, it wouldnt do it when idling just on take off at low speeds, not wanting to be stranded somewhere again i took the cam and lifters out again and the cam lobes were worn again as well as 2 lifters mushrooming at the bottom, i took engine apart again and repeated procedure with another melling camshaft and lifters, same joe gibbs oil with wix oil filters, within 1k miles ANOTHER failure of the cam lifters, took it apart again recently, this time i bought a compcams high energy camshaft with sealed power lifters from summit, same joe gobbs break in oil and joe gibbs hr oil for after break in oil, it developed another knock at low speeds within 500 miles, it hasnt completely failed yet,but i know its coming soon with the knockings its doing,i am at a complete loss of words as to why this is happening, i studied and followed break in procedures to a T with highly recommended oils, each time after i installed cam and lifters the engine would run smooth until they started knocking at low speeds and then short after i get the lifter and cam failure. What am i doing wrong? The 2nd time they failed i got a flashing CEL showing misfire in multiple cylinders and started knocking LOUD

 

What company was that?

Check the lifter bore clearance.

 

And then I'd call up Melling and Sealed Power Tech Support and see what they think.

 

Or maybe you have (had) 2 separate issues. Take off the valve cover and see if oil is flying out of everywhere where it's supposed to.

 

They are promar precision engine. How would i go about checking lifter bore clearance?

 

when i originally primed the oil pump with a flathead on a drill oil came up through all the rockers, and removing the valve cover now there is still oil coming out of all the rockers, a couple rockers its coming out a little fast (shooting up high) but still getting oil on it

 

Get a dial bore kit:



and a good micrometer.

Tappet Bore Diameter 23.000 to 23.025 mm (0.9055 to 0.9065 in.)

Hydraulic Tappet Diameter 22.962 to 22.974 mm (0.904 to 0.9045 in.)

Tappet-to-Bore Clearance 0.025 to 0.063 mm (0.001 to 0.0025 in.)

 

I feel your pain brother.

If I was you, I would obtain a used XJ engine and install it

Unless you are very unlucky, this should solve your immediate problem

You obviously have mechanical skills so can do it yourself

A used engine probably would cost about the same as the new parts

You can then figure out your next move in a reasonable time frame

I did this with another vehicle I owned, purchasing a used engine for $300, (then found out it had been the subject of a high quality $5000 rebuild)

 

Promar Precision Engines? They're just up the street (give or take 70 miles) from me!

IIWM I'd call them up too and present the problem to them. Seems to me their lifters would fit their bores, so perhaps the sequence of events was the first set wasn't broken in properly, but subsequent sets are too... something. Hopefully the measurements will identify the issue, and getting Promar parts (or equivalent) will solve the problem.