Ignition issues '70 340

[Kevman89]

Hey guys, I recently did a top end rebuild on a 70 340 for a buddy. It was running great until we were stuck waiting for a train, and the coil got really hot and quit until it cooled.
We limped it home and it was okay, a few days later on a hot day, it did the same thing, this time it runs for a second and shuts down. Changed the ballast resistor, same issue. Is it a bad coil? I ordered an MSD blaster 2. It's a Mopar ignition and distributor.

 

[70ChargeDodger]

My car was heating up and dying and then running again when cool, ended up being the ignition pick up in the distributor, good luck.

 

[440Coronet500]

Do you have the correct value (ohms) ballast resistor for the MSD Blaster coil? 440'

 

[dvw]

Could be the coil. I'd check the pickup coil gap (.008"-.010")
Doug

 

[451Mopar]

Sounds like the coil, but could be several things. Electronics don't like high temperatures.

 

[Kevman89]

Changed the coil, and the ballast resistor. Most we got is two revs before it died. Fires on the first hit, but will not continue running.

EDIT

tried running a hot right from the battery, wire was extremely hot like a short

 

[Kevman89]

FIXED

ballast resistor was backwards, from when we changed it.

 

[Nacho-RT74]

Ballast resistor doesn't have a "backwards" sense. Resistors are bidirectional. Unless we are talking about dual ballast, in that case resistors could be reversed, but still plugs have a key and ceramic got a slot to prevent that. Unless plugs are without the key

 

[Kevman89]

Ballast resistor doesn't have a "backwards" sense. Resistors are bidirectional. Unless we are talking about dual ballast, in that case resistors could be reversed, but still plugs have a key and ceramic got a slot to prevent that. Unless plugs are without the key

View attachment 972166

That's exactly what it was.

 

[451Mopar]

Is your ignition module a 4 or 5 pin unit?

 

[Nacho-RT74]

That's exactly what it was.

But something was wrong there because the key on plug and the slot on ceramic won't allow you to conect them backwards. UNLESS, the key is broken on plug, which is posible because being old and the heat on the ballast causes to brittle and crack.

When I say backwards I say up and down, not side to side. Side to side makes no difference.

Replacements are available around
https://www.megapartsusa.com/proddetail.php?prod=102-Q1

And save that mistake again.