After a lot of Googling earlier today, I think the relevant question is, "What defines the "D" in B230 FD?"

Till now, I'd assumed that the round-tooth belt on my '93 940 had a 100K replacement interval, based on the conventional wisdom here. But jthorner's posting of his "Timing Belt Replacement Interval" chart in another thread, prompted me to check my '93 940 owner's Manual, which says that the B230F interval is 50K, with a footnote 4 reference.

Footnote 4 says, "B 230 FD only. . . belt should be replaced at 100,000 miles."
Note that this same distinction is shown in jthorner's chart.

So do I have a B230FD? I don't think so, with 88 in the VIN (6th and 7th digits) and nothing on the t-belt cover except the "L" for piston cooling. I spent some google time earlier, trying to find out what that "D" means, but found nothing definitive. Does anyone know what the D means, and where would it be identified on the engine?

In any case, it appears that the round belt teeth does not (and never did) relate to or define the belt replacement interval. Nor has it been revised, as suggested elsewhere in the thread linked above.

--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.