Arcing Dyna Coils Added pics

[73 sport]

   I've had Dyna coils and distributer plate on my '74 Sport since the mid '70s. never a moments problem. I have silicon rubber plug caps, the insides are lightly coated with silicon grease. The coil caps are also coated inside with silicon grease. Many of the gripes I've seen on this site looks like rain, humidity intrusion. Not all ignition wires and caps can handle higher voltages produced by performance components. The complainers seem to have similar problems, they don't want to spend the money for quality components.

[baloo]

Yes, Any update?
I'm having the same problem of backfiring at higher rpm - I have the Dyna system, which ran great until parked about 1yr ago. 
Thinking it might just be the coils (Dyna 5ohm) which test out OK per static tests with multimeter.
I'm thinking the coils just might peter out at high rpm (when I get backfiring - around 6000rpm)

Carbs cleaned out

[73 sport]

    Go to Google. Type in "What causes backfire at high RPM".

[Turin]

It's not the Dyna ignition or the coils. Both have been swapped. Not the carbs either, those were swapped.

IOt has to be the NGK (racing) plug wires

[michaell32]

Weak valve springs cause this issue. The valves could be floating it the high rpm.
Edit: Nevermind. You already answered the other comment.