engine (electrical) quit cursing at 70 mph

Driving down the Hwy at 70 mph for about 30 miles and all of a sudden total failure. 73 Electronic ignition 340.
After a few seconds started up again on its own.
Happened again a little while later but drove another 60 miles and not an issue.
Other than a possible bad ground, any other suggestions?
THANKS

I'm thinking dist pickup or possibly the coil. do you have any spares that you could sub in for a test?

Did the engine just die or did you get a fluctuation in the electrical system. By fluctuation I mean did the light flicker, the radio cut in and out, etc. Lights will dim when the engine dies but not usually flicker.

How long before it restarted?

Several things come to my mind right of the bat.
#1 on my list, Bad Ignition box.
#2 Bad Connection in the electrical system. Check all connection especially the bulkhead, wires to the distributor pickup, and the disconnect at the steering column for the ignition switch. Don't forget the battery.
#3 Ballast Resister going bad.
#4 Bad Pickup coil in the distributor.
#5 Coil going bad
#6 Fusible link going bad. Fluctuations/flickering is common. it should not be crispy or feel crunchy when you flex it.
#7 Wiring harness going bad. Check for crispy wires on both sides of the bulkhead connector, connecting to the Ammeter in the dash, and in the harness that runs along side the valve cover going to the Alternator.
#8 Bad ignition switch.

Hope it helps.

"#1 on my list, Bad Ignition box."

100%

It's not an orange box by chance is it?

The last ECU I had go bad would cut out and fire back up when going down the hwy. Made for one heck of a backfire because of it!

You mentioned ground, make sure the ECU has a good, solid ground. On my drivers, I'll run a braided ground strap from the block to the ECU and use a nut and bolt with a star washer to fasten it to the unit.

Do you curse a lot below 70 mph? Must be rough going thru school zones.......

Not an orange box.
Did backfire and fried part of the engine harness by the carb

both new

no flicker. Just dead. No radio, tac to 0, gauges off

There's the clue. Look at which wires got fried.
Wires that overheated internally did so because of too much current through them - usually due to short.
In other words one of the conductors or something it was connected to touched another wire or ground.
IIRC '73 begins the electric assisted choke, so that is one possibility, but go by what the wires show, not some guess from a guy who can't see what you see on the car.

I had a coil backfire & the guy next to me almost went into the ditch, he musta thought he was being fired on!

Mattax
Thanks

The wire that connects to the choke control switch is now bare and melted the the harness tape for well over a foot.
I'm curious why you pointed it out in your comment. Is there a standing issue with it?
Thanks

Like mattox said that is your problem. The backfire didn't burn the wire the burning wire probably caused the backfire.

The wire that goes to the choke control is also the same wire that powers the Alternator field, Ignition ECU and Ballast Resister which powers the coil. When that wire burns a lot of systems get shorted.

Basically everything that "turns on" when the ignition switch is in the run position is on that wire.

The only fuse for that wire circuit is the fusible link. Check it for damage.

trace the harness back to the bulkhead as well, and see what those connections look like.

I'm not aware of any widespread issues with it. Its just that the electric choke was added to the ignition circuit and the ignition circuit is not fused.
If the other items in the ignition circuit shorted, that too would have killed power. But that one is near the carb.
see if there additional clues - like if the conductor touched ground, the copper should show spot damage from the amperage.

I agree its worth looking for damage all along the path.
I'm not that familiar with the '73 choke assists, but I'd want to check that the short wasn't internal.
The other thing to check is the fusible link. While there is not fuse on the circuit, the fusible link could have melted.
If the fusible link is melted, then definately check the other terminal connections.
http://www.heritech.org/cuda/Charge2.html

edit: Service manual shows the choke and choke control wires to be 18 ga, far less than the fusible link. So they should have melted before the fusible link.