1972 cuda turns off after running for over 20min

[cmesa]

Hello,
I have a major problem, when my car (1972 Barracuda 4 speed) runs for a while it turns off and will not start. I checked for spark going to plugs- did not find any. I changed the coil and it starts. When I let that coil run it also turns off, then I plug the first one back and it starts. I can do this all day long. i have replaced alt., coil, electronic box,... What can cause my coil to do this?
Thank you all  in advance for any help.
Chris

[anlauto]

Are the coils really hot to the touch when the engine quits ?

[Chryco Psycho]

Dist pick up coil can do that , the gap should be .oo8 between the pick up & reluctor

[jimynick]

Hows the coil mounted? Is it on it's side? There's been some info that the current coils have the oil run away from the core when on their side and that causes the coil to overheat and kak. It'll cost you nothing, so mount the coil standing up and see if that cures it. Let us know. Good luck 

[dodj]

Ballast resistor been changed? It is a heat component in that it suffers from heat degradation.

[JayBee]

I had an orange ECU do that to me once. The car would run fine, then after some time it would shut down and only restart after a cool down period. Are you sure it's the coils? Funny that both would react the same way. Maybe you have the same scenario I did and by the time you swapped out the coils the ECU cooled down enough. If you could temporarily swap a known good ECU in there that will help further help isolate this.

[1 Wild R/T]

Dist pick up coil can do that , the gap should be .oo8 between the pick up & reluctor

Listen to this man, it's a common issue......

[cmesa]

Hello,
The coils do not get hot. I attached them to the firewall, upright. I did change the ballast resister.
 I am going to try getting another ECU and try to figure out how to check the gap in the dist. pick up coil.
Thanks to everyone

[dodj]

Hello,
The coils do not get hot. I attached them to the firewall, upright. I did change the ballast resister.
 I am going to try getting another ECU and try to figure out how to check the gap in the dist. pick up coil.
Thanks to everyone

non magnetic feeler gauge. screws in the pick-up plate allow adjustment. adjust so that there is just a little resistance as you remove the gauge (from between the pick-up and reluctor). at least that is how i do it.

[tman]

Feeler gauges are made of brass and can get them at any auto parts store.  Forgot where I got mine several years ago.