The Stovebolt Site Forums The Shop Area The Electrical Bay Distributor for '59 GMC truck with 270 engine

... and once you get a distributor mounted, MAKE SURE it is seated all the way in. I have a story about a hot-rodded 270 that a shop who wasn't familiar with our inline sixes that ran for about 5 hours with the distributor not plugged all the way into the oil pump. It finally worked its way out enough to disengage from the oil pump, but still was engaged with the drive gear on the cam. The engine seized.

A friend and I tore it down and found the following:

I did not duplicate the “No oil pressure suddenly after 5 hours of run time” problem. It appears that the distributor was not properly installed and “rode up” over time until it was high enough that the tang on the end of the distributor shaft no longer engaged the slot in the oil pump shaft. The distributor was out of the engine when we picked it up so we cannot be sure this is what happened, but witness marks on the end of the distributor shaft support this theory. We used air pressure to test for gross leakage and when we found none we used a ½” drill motor and a homemade shaft to turn the oil pump. Oil pressure reached 57 PSI at an estimated 600 RPM (1200 crankshaft RPM) and stayed there (being regulated by the oil pumps over-pressure dump valve) to the 850 RPM max of the drill motor. We found no unusual leakage pressurizing the system with either air or oil. The design of the distributor and its hold down mechanism is such that it is possible to install the distributor in the block far enough that the gear meshes with the camshaft gear, but the tang is not in the slot of the oil pump. That would allow the ignition system to work, but not the lubrication system. It is also possible to install the distributor at the proper depth, but not properly secure it in place. Over time it could work its way up in the block and eventually come clear of the oil pump (oil pressure drops to zero) while still has about another 4/10” of vertical movement before the gears don’t mesh and the distributor quits turning causing no spark and the engine dies.

Edited 6/4/24 20:00 to REMOVE A LOT OF OFF TOPIC INFO. SORRY TO REMOVE ITEM #12 WHICH HRL REFERS TO BELOW.