3rd camshaft+lifter replacement, tapping noise at 2500-3000 rpm

[FlexJ17]

Purchased a reman stock 4.0l long block from a reputable source at the beginning of this year. Had a shop install it, 500 miles later the camshaft+ lifters took a shit (when i removed them you can clearly see damage to the lifters and camshaft lobes) so i replaced them with a stock melling camshaft+lifter set within 100 miles i was getting a rotational knocking noise on acceleration inbetween 2500-3000 rpms, so i took that camshaft+lifters out and i didnt see any visible damage to either like the first set i took out, regardless i bought another new oem camshaft+lifter set, made sure eevrything was lubed up correctly and used joe gibbs break in oil, then after the initial 20 min break in i changed the oil to joe gibbs hr oil. I am about 300 miles into the 500 mile oil change and it has developed the same tapping inbetween 2500-3000 rpms, jeep runs good besides the noise at this point im thinking its something other than the cam+lifters but i have no clue. The tapping is kinda silent but its definitely there.

 

[Unclewolverine]

My persistent tap I thought was lifters was a rod. I know its a new motor but people screw up. Also could be cracked flex plate.

 

[RCP Phx]

Two things, first go back to high ZDDB oil for 1000 miles, second have you checked your lifter pre-load?

 

[FlexJ17]

@unclewolverine, how would i go about diagnosing the rod knock directly? And as far as the flexplate, the first time i had the cam failure i decided to replace to camshaft bearings as well because i knicked them pulling the cam out so i removed the trans and had the flexplate out and it was still in good condition with no cracks

@RCP Phx
The oil i have in it now and the break in oil i used both have high zddp and phosphorus joe gibbs driven oil as far as the lifter preload, whats a good way to check that? With a dial indicator im assuming?

 

[RCP Phx]

whats a good way to check that? With a dial indicator im assuming?

That's is the only way!

 

[Unclewolverine]

Only reliable way is pull the pan and plasti-gauge the bearing clearance.

 

[CJR]

Some comments on camshafts;
1. The OEM camshaft lobes on older XJs were dimensionally wider. Many after-market camshaft lobes were reduced in width. There were a number of threads on this with photos of the significant reduction in XJ lobe widths. I've taken OEM wide lobe width cams and had them reground by Comp Cams and had good results.
2. A while back there were lots of camshaft failures and some lifter as well. Apparently, a manufacturing problem because the cam manufacturers replaced them very quickly w/o charge. I had a Crane cam go on me and got a very fast no charge replacement.
4. Many reman engines are not balanced. Wear is dependent on how badly the engine is out of balance.
5. There are many small shops that grind cams for the big camshaft suppliers. So, in some cases, you don't really know who made the camshaft. In the past, I used many Crane cams until they had their ownership problems. Now I use Comp Cams and occasionally Edelbrock Cams.
6. A proper grease coating ,on the camshaft lobes during assembly, and pre oil-lubing the engine is very important before firing-up the engine. Likewise, the proper "cam break-in additive" added to the engine oil is also very,very important. Once the engine is fired-up, the engine needs to be kept at a steady 2000RPM for about 30 minutes. When done properly, the surfaces of the cam lobes and lifters are "broken-in"/mated to one another. If possible, two(2) people should do this; i.e. one to keep the RPMs at 2000RPM for the 30 minutes, and one to keep checking the engine for leaks.etc.

Hope this helps.

Best regards,

CJR