Veddy intedestingk!!

It amazes me how we always tend to jump right on the "carb/fuel system" wagon when we start experiencing problems like this. I have that tendency, and I should know better by now. That is not to say that it couldn't be fuel related, but quite often, an electrical disturbance in the ignition system is found to be the real culprit.

As to the failure of the "box", lasting through three years of heat and vibration doesen't seem unreasonable, nor does it's failure, all things considered. Electronic components are, by their very nature, less tolerant of errors in manufacturing than mechanical devices, and are more sesitive to their environment regardless of the efforts made to engineer them to not be so.

Something else that I picked out of this discussion is our continuing tendency to use mismatched components in system environments. In the old days, we'd get a dual points conversion for our distributor, of some brand or another, very often a Mallory "high voltage" coil, some Packard real copper plug wires, and whatever variety of cap and rotor we could lay hands on, and it all seemed to work just fine - but, it was all mechanical and basic electric stuff; sort of "clank" compared to todays engineered systems "ting". Today, a Mallory controller box is undoubtedly developed using all Mallory components, and made to work with them as a system. Even though the basic principles may be the same, an Accel, MSD, or other brand of system is developed using their own proprietary components, and mixing them is adding a lot of potential for error and failure due to mismatched engineering into the system. It does not take much to give a PC board the "willies".

One other thought, and I'll get of of my "old fart" soapbox: Have you considered moving your "box" from the engine compartment into the inside under the dash where it will not be subject to the relatively extreme heat? Electronics don't seem to like heat very much, and the might improve the longevity of the box.