Conversation Between stevejohnson48 and 390fe

Steve, I don't check in here often, sorry for not getting back to you sooner. I used the wiring diagram found here:
Duraspark II Conversion Basics

This schematic does show a capacitor being used. In either case, the capacitor was used to try to prevent any unwanted spark/ignition noise from interfering with a vehicle's radio. It will certainly not hurt anything by leaving it on there, in my opinion.

Probably the single most important thing is to be sure that the coil is getting the proper voltage. Ford ( cars and light trucks) used a resistor wire to drop the voltage down a bit so the coil didn't overheat and cook itself. I replaced my wire to feed my coil the full 13.8 +/- volts. I have not had any failures or issues since installation, years ago.

Good Luck,
Jason Kendrick

hay,I'm running a 390-30 over in a old v-drive drag boat that I restored switched in a 76 duraspark distributor & ICM,I was running the same coil (with a external capacitor that I ran on the points distributor,and it seem to run fine for a while,then I was talking to this mechanic and he seem to think that this ignition system doesn't require a capacitor I'm also looking for the wiring color code for the (schematic)for wiring this brain box (wanting it right)give me some feed back..../ Steve