Coils are oil-filled - you can shake them and hear the oil inside.
Check for ANY leakage or oiliness, especially around the coil wire to distributor attachment. If it leaks, it's bad.
Testing with an ohm meter goes like this:
Primary resistance test:
Set your meter on ohms. Touch black lead to (-) terminal and red lead to (+) terminal. Reading should be between 1.0 and 1.7 ohms.
Secondary resistance test:
Set your meter on Kilo Ohms. Touch the black lead to the center coil wire terminal. Touch the red lead to the (+) terminal. Reading should be between 7.5k and 14.5k ohms.
Here is a video on Youtube:
https://www.youtube.com/watch?v=Rk1q3LHHQow
And here is a diagram showing the test specs you're looking for on a stock coil:
https://contentinfo.autozone.com/zne...coil_specs.pdf
If it's an aftermarket coil, you'd want to check what the specs are from the manufacturer, but you'd test the coil the same way.
Examples:
Accel Super Coil (the great big yellow one) #140001
Primary resistance 0.7 Ohms
Secondary resistance 11.8 k Ohms
Accel normal size coil (chrome and yellow)#8140 or 8140C
Primary resist 0.7 Ohms
Secondary 11.8 k Ohms
MSD Blaster 2 Ignition Coil #8202
0.7 OHMs Primary Resistance
4.5 K OHMs Secondary Resistance
My guess would be on the module inside the distributor is getting too hot, but I'm not sure what the test procedure is for the MSD modules
MSD is owned by Holley now. Customer Service is 866-464-6553
Here's a link to a 150+ page PDF for troubleshooting.
https://documents.holley.com/techlib..._wdtn_2014.pdf
Good luck!