Based on comments by Rockman59 and PaulSpringman, it appears the valve seals (and perhaps guides) are an inherent weakness in the 560 powerplant.

__________________
Mike

82 240D 97K Original (Sweet)
96 Ford F350 CrewCab Dually,7.3 PowerStroke,144K
(a real workhorse, does anything I need)
04 VW Jetta GLS TDI, 33K (50 mpg & it's quick)
Notice a trend? All diesels

63 Chevy II Nova Convertible (wife's) awaiting restoration - Well everyboby has a little gas every once in awhile