I just installed a mallory hei I am running a 14g wire from the bat to a in line fuse to a switch inside the cab then to the distributer. My question is what size fuse to use? I've heard everything from 5a to 60a. I do not want to fry this coil or melt any wires or dumb **** like that. I put a 10a and as soon as I flipped the switch it poped. I guess I'm going to try a 15 next and work my way up till something works. And no I am not using any stock wiring harness at all on this build

 

if the fuse burnt, there is a wiring issue. a larger fuse will only cause a fire. Backwards wiring on the coil can cause this.

 

Naw I figured out the problem the way the diagram was written is a little funny, it had a ground symbol where the tach is supposed to go, that's y I had no spark. The fuse popped because it was only a 10a and it needed to b 15