I have a 305 with non-computer HEI dist. It started by intermittantly losing spark. No pattern at all - I replaced the entire dist. with a junk yard pull and it worked for about 3 months.
Now it is hard broke - starter turns engine but zero spark. To make a long story short - I checked every component in both dist. and can spin the cam drive gear by hand with 12v and ground on either dist and get fat spark. Out of the car, they both work, in the car, neither works. I even ran 12v directly from the battery and installed ground wire from HEI coil frame to engine. No spark. Any clues?

 

BJ2,

Welcome Aboard!

Sounds like you have two good distributors, and possibly a problem with the vehicle wiring. Try disconnecting the TACH lead to see if you can generate spark. Something is likely dragging the primary voltage down, and that's a place to look.

Does your distributor have the flat, four-wire connector for the primary connections?

 

Thanks vader, I think I have eleminated all the vehicle harness by disconnecting the tach and BAT connector and running a 12v line directly to the battery POS. terminal. I also ran a ground wire to the HEI coil frame. I used the same 2 wires when I turned it by hand and produced fat spark.

Could the speed of rotation cause such a difference. I tried turning it as slow as possible by hand but I doubt that I could duplicate the cam drive speed which would be pretty slow.

Could be that the starter load is dragging the whole 12V circuit down - this seems to be the only different factor between spark and no spark. Don't know how I would check that.

Baffled??