I have a '64 F250 with a 70something FE 360, 4x4, np4350. I'm not getting spark in 2 plug wires at idle. Oddly, it sounds fine at idle. When I give it throttle I get spark in the 2 wires but it doesn't seem smooth and continuous, it seems erratic and weak which I suppose is why under load it's sputtering and popping. I have a new dist. Cap and new plugs and wires and new coil, truck ran great for a couple months now this. I had put a new coil in a few months prior to this one and it went bad. Both were napa coils. I'm planning on modifying the ignition system with MSD coil and distributer. Any input from you guys would be helpful; I don't want to replace all of this and have a reoccurring issue.

Also if any of you are familiar with ford's XPI "extra power ignition" box I'd love some input. If I use a blaster II coil do I still need the box? Could that be causing any of my issues?
Thanks for all your insight in advance!

 

By chance do the wires for these two cylinders cross over each other somewhere? Laying on the headers? Rubbing up against metal? Poor quality or old wires can leak the spark. Sometimes where they cross each other the spark can actually jump through the insulation and in to the other wire.

 

BTW, Welcome to FTE!

 

They are new wires. They don't actually cross. They are right next to eachother on the distributor though.

 

I know this stuff is new. Quality of new aftermarket parts can leave a lot to be desired now a days. Since they are next to each other maybe the spark is jumping. Try looking close on the inside of the cap for a crack or carbon trail between or around those two terminals. Also to see if the spark is leaking or transfering on the outside of the cap check it in the darkness of night. Fire up the engine tonight and with a spray bottle full of plain water lightly mist over the Dizzy cap and along the two bad cylinder's wires. If the spark is leaking or transfering the water mist will give you a light show.

 

I will do that tonight and get back to you. Thanks for the tip.