Reply to "Role pin for distributor - setup unclear"

i guess I've been around, I've seen several of the circumstances listed here that lead to a DGRP (distributor gear roll pin) failure. 1965 289 Mustang i was giv'n her what she got when the oil screen found a #8 lock washer from who knows where & let it pass through the relief hole under the metal strap of the std screen assy. Yes there's a hole in the screen under a metal strap if you can believe that, same style as the 351C-2V oil screen. so NO the lock washer did not navigate the pump when it came to the smash your oil flat section of the gearotor meshing and the OPDS (oilpumpdriveshaft)did it's best impersonation of a barber pole as shown above but it did not break before the engine shut down due to the roll pin fuse letting go

the roll pin acted as an oil pressure switch

another time was the same thing debris in the pump stopping the works but a single strand of a wire wheel? YUP a tiny little wire wheel strand stopped the oil pump & broke the DGRP. this time the OPDS did not twist at all and was undamaged probably due to low rpm at the time of the incident. this was a late model 70's smog 302 IIRC

then there was the time i had 20-50 in my own 351C, the weather was getting cooler and i had fouled spark plugs from chokeless operation of a dual quad tunnel ram. so during an attempted start & warm-up of said beast, the fouled plugs coughed one time too many / too hard & stopped the fun for that day ... broken DGRP. this engine broke the DGRP multiple times before i regained my senses & used proper grade oil. and YES it was an HV pump btw

note that all instances are outside of normal design parameters ie; trash in the oil and oil grade not correct for conditions

also note that due to the failure of the DGRP all incidents were easily repaired and the engines were back in service quickly, none required complete rebuild due to operating with no oil pressure as they may have if they kept running after the oil pump stopped turning. nor did any damage the drive gear on the camshaft as they may have if the DGRP remained intact causing a failure of the distributor gear itself

YMMV (your mileage may vary)