Distributors Failing
 

'76 Bronco with about 3k miles on the 302 engine rebuild that was completed a few years back. Not driven much as you can tell. I'm experiencing an issue that I haven't been able to solve quite yet. I'm on the 4th distributor. Cam is a Comp Cam (31-230-3). The distributors that have been used are from O'Reilly - Spectra Premium (FD09) with cast iron drive gear. After a few months of driving around they just fail. So far two shafts have broken internally within the distributor. The 3rd one was starting to stick. I could tell it was getting ready to break due to it started bogging down, sputtering and such. I dropped in a 4th one, and it starts right up and runs fine. Drive gear on all have been perfect.

Any ideas on what is causing the dizzys to fail? Are the Spectra's really that bad. Need any thoughts you guys may have for this one.

Exactly where did the shafts break/separate?
I would think depending on where the shafts broke, oil not lubing the dist shafts or again keep in mind, that shaft drives the oil pump or a possible problem with the gears on the replacement distributors.
When the rebuild was done , were any of the cam brgs replaced and the oil holes not lined up?

It seems to be in the main shaft below the base but above the drive gear. So you can't see that it's broke. However, you can turn the rotor and the drive gear doesn't turn. There is oil on the drive gear but I guess it's possible that it's not getting oil internally. I believe the Spectra is a sealed unit. In regard to cam bearings, I believe they were but it's hard to say. The paperwork doesn't get that detailed.

Please consider trying this,
with any dist you have out,
there is a rolled pin that holds the gear to the dist shaft. Not uncommon for that pin to shear and the best way to check is to see if you can shoot a piece of wire through the rolled pin to confirm it isn't sheared. If that is found to be the problem, it could be caused by a problem with the oil pump or poor quality rolled pins. Let us know what you found.