I’ve got a 1992 12v Cummins manual 4x4 that’s making a strange noise. Things done to it and kdp, 2 gen lift pump, 3200 rpm spring, slight timing bump. I first noticed the noise after doing my head gasket and valve seals. I’m not positive that it’s a new noise or I just noticed it because I just did the head gasket. Things I’ve checked are reset the valve lash three times, pulled push rods out to check there straight, crack one injector at a time to see if the noise leaves, run it with the belt off. Nothing seams to help. The weird thing is the noise is not there when I first fire it up in the morning but comes back after a minute or two of running. Motor seems to run fine and has little to no blow by. Any help would be much appreciated thanks