They don't tighten, the gap gets more narrow.

Is that because of valve face and seat wear? If so, I wonder how long they can actually last.

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RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

That would be the logical explanation, I can't think of anything else that would cause it.

Agreed, no torque values from MB.

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83 SD

84 CD