Same thing happened to me. I ended up stripping two valve thrust nuts. Had to replace them. Barely squeaked by with enough clearance. Replacement valve thrust nuts seemed to give me the additional clearance, but that was it, no more. I will probably have to grind down the top of the valve for the next adjust. I think the valves are just wearing into their seats more. You might have a shrouding effect on the valves, but im not too concerned, because the air charge is pressurized. Im sure someone will argue that.

Hard to say its the end, my car only uses about a quart of oil every 10000 miles. And thats including a leak(dribble).

If you accidently strip the nut, thats ok. Only the threads on the nut will give, the threads on my valves were intact.

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airedale2 Welcome to Texas
1984 MB 300D 266,000
1993 Nissan PU 271,000
2002 Tahoe 122,000
2004 VW TDI 75,000