what could cause a distributor cap and rotor to become liquified while driving

 

No idea. never seen that.
Does the heat damage on the cap offer a clue, like is there more damage on the inside or outside of cap?
Are the components Denso? odd looking rotor.

 

more damage inside,I know its weird,

 

cheap junk rotor, and/or an engine that's running too hot, something heating up the distributor drive shaft?

if you've experienced old engines with points-based ignition, the cam lube for distributor drive shaft is special high-temp grease.

 

Any mods or changes to ignition system? Still wondering about brand of cap and rotor. As OSV speculates, a poor quality rotor and cap are my only guesses, unless you've made mods you haven't mentioned

 

Any update?

 

No theres no mods to ignition,the cap and rotor are from orielly's,used them for years and never had a prob.,distributor itself is oem.. I have no idea what happened,i've never seen that before

 

I'd get a Denso cap and rotor. There really is no other apparent explanation that I can think of

 

I'm not going to disagree with Denso, but to melt even a low-grade piece of plastic is going to require a lot of heat.

The only "likely" source of that heat that I can think of is a failed bearing. Pretty easy to check; pull out the distributor and turn it with your fingers. [BEFORE you pull out the distributor, turn the crank to TDC, with the (remnants of) the rotor pointing to #1. If you follow the FSM on installing the distributor, it will end up in the right place. Or, since the helical gear has 13 teeth, you could be off by about 28°]

 

I pondered a distributer starting to seize, but I'd think that's be noisy, and metal would be discolored.

What about poor contact between the cap and rotor?