My buddy has a 1999 Dodge Durango with a 5.9 Magnum engine. The engine has all new main bearings, rod bearings, oil pump/screen, cam, lifters, timing set. but, it has a very noticeable knock (the same knock was present before the rebuild), however, it holds excellent oil pressure and has been driven over 20,000 miles since he purchased it (it made the noise when purchased). It runs strong and doesn't miss a beat. The oil pressure, and length of service without issue leads me to believe it is something minor. He removed the valve cover and retorqued the rocker bolts, which did do away with the noise, however about two days later it returned, so he went to retorque them again thinking they backed off, however they were still at their original torque.

This is what confuses me, the knock is obviously related to the rockers/pivots/bolts, at first I suggested to him it was a rocker bolt stretching, but if it was a stretched bolt it would no longer be torqued to the same spec, correct?

A bad lifter would also be another place to look, but, the lifters were only replaced after the bottom end was gone through and the noise still remained. Changing the lifters and cam didn't help the problem either.

I'm a GM guy (be gentle), and I'm not too familiar with these engines, so any help would be greatly appreciated, thanks!

 

piston slapping the head, stud has pulled up, pistion pin knock.

when the noise is present, try killing a cylinder at a time & see if the noise is affected. if no=valve train, if yes=lower end.

If he reused the pistons & rods that is where I would suspect the issue is.

 

These don't use studs as they are fixed lash and non-adjustable.

Though a while back we did a cylinder balance test and it had no affect on the noise, which is why like I say I suspect the valvetrain, but all the rocker bolts remain properly torqued, the rockers show no obvious hairline cracks or sign of uneven wear and all sit properly when in relation to the center of the valve stem.

 

Sounds like a piston to head tap as Dislander is stating.


Take a look in the cylinder through a bore scope and see if it's tapping.