I had the same issue with the jam nuts loosening several years back with a hydraulic roller cam set-up in my 493 RB. It dropped a pushrod too. In my case, the springs were loosing control of the valve train at about 5700 rpm or there abouts. There was some seriously bad harmonics going on in the valvetrain. They were so bad that it blew all the roller bearings out of my exhaust rockers.

I sought help getting to core problem from Dwayne Porter, He guided me through the analysis process, identified the root issue and then went through my heads and spec'd a mechanical roller cam. The motor has never run smoother or performed better.

I even ended up using B3 Racing to optimize my rocker geometry. Mike, the owner, is a great guy to work with.

I also found that be tightening and loosening the adjuster nuts several times to really seat the lock nut on the rocker arm helped keep them tight.

What did they do to fix it?

Basically, I swapped over to a mechanical roller so I could run enough spring pressure to control the valve train at higher rpm. With a hydraulic roller, there is a balancing act between running enough spring pressure to control the valve train with hydraulic lifters, but not so much that the lifters collapse.

On big block Mopar's the hydraulic lifter choices are pretty limited. If you plan to stay bellow 5500 rpm or there abouts, the stuff that's out there is fine. Some guys can bump the rpm up higher, but for most folks that's about the upper limit..

I needed something that is happy in the 6K+ range, so mechanical roller was my best path.

I also put in a set of Manton Stage 5, 7/16ths pushrods and custom T&D rockers with B3 Racing's geometry correction kit. The engine has never run as smooth as it does now. I think a lot of the difference is due to how stable and efficient the valve train is now.

Here's a before and after pics the B3 geometry correction kit.

I have T&D rockers with B3 correction

I just got of the phone with Crane cam. I have a new lifter on its way! He thinks maybe the lack of maintenance is why it came loose. It runs to good to change a bunch of stuff, so I am going to replace that lifter and adjust all the valve and see if thinks stay together. Remember it has not had a valve cover off since 2001 or 02 and always fired right up and will run low 12 seconds and I shifts at 6500 rpm when I raced it. Thanks for all the help!