Bit of an update. After the DV thread, I yanked + checked mine and compared to photos in the thread. All looked fine, no pits or ridges or anything. Even consistent grey area where the DV contacted the seat all the way around, and that's it, on all five.
Fooey. I know it's silly to be hoping FOR a problem, but after years of chasing this issue around I was really hoping for something here. Some clue as to WTF is going on.
Then upon reassembly and inspection, EUREKA.
A SCRATCH ON THE DV HOLDER SEALING SURFACE!!!!!!!!!!!!! Deep enough to catch a fingernail in. About 4:30 in the pic.
Yanked a DV holder from my spare engine(which I was really wanting to keep intact, hence my asking for someone to sell me a DV holder above) and swapped it in.
I am cautiously optimistic. Lots of times before I've done something that's made a positive difference for a short period, only to have the problem crop up again shortly. That said, this is MUCH better. Best it's run in years. Random rattle upon acceleration is gone. Rhythmic tapping when coasting down has been almost entirely eliminated and is well within acceptable levels. No more people looking over wondering if they'll get to watch my engine explode or if it'll last long enough to get out of sight first. Weird Cummins-y idle sound is still there. Much more smooth at idle.
