Dual points were there, in the first place, to extend the dwell time for a hotter spark. More time for the coil to "make volts" before the plug fires. Can't do the same thing just by changing the point gap outside of the gap specs, so one point set opened things and the second set closed things.
Pontiac allegedly did a dyno test to see if dual points were really needed, back about '66 in the pre-OEM electronic ignition days. They allegedly found no real difference in power output. Up to 6000rpm or so. Dual points were not meant to allow for higher rpms, just better firing at higher rpms due to the increased "coil saturation".
There was LOTS of aftermarket hot rod ignition stuff floating around in the middle-late 1960s. Much had marketing hype attached to it, plus wild cosmetics/heat sinks/bigger sizes. More spark voltage is always better? BUT, as mentioned earlier AND by a Holley engineer (at a seminar in the 1980s, or was it Jacobs?), the coil only produces what the plug needs to fire . . . no more, no less. But then top fuel drag motors needed magnetos for their reliability and max spark output, in their high-pressure combustion chamber environment. But then farm tractors used them too, as did some earlier 1960s drag racers. Simple, easy, lots of zap.
One of the design parameters of the GM HEI was to have enough "zap" to fire a .100" gap plug (in the typically 8.5 CR range, of engines at that time). It was discovered that when the plug gap got past about ..80", plug wire condition became critical. Some Olds V-8s spec'd a '060" gap, but after a few cycles of fast idle with no warm-up, while being moved around the car lot, the plugs would foul and the gap was tightened.
Having the HEI module coated with "heat sink lube" is important, or the module will cook itself. Otherwise, generally no other problems. The center carbon electrode in the cap will wear out over time. One winter, it got really cold and a customer's C20 work truck wouldn't start, although it ran the day before, when it was warmer. The carbon piece was not there. There was evidence that the coil still fired, not always hitting the right point on the rotor's center spring. New cap and carbon item and it was good again.
The larger diameter of the HEI cap is there to decrease high-speed misfire tendencies. Which was later attributed to in-cap ozone production from the stronger sparks. Fix? Drill holes in the cap for ventilation.
Well-cared for points usually lasted about 20K miles, back then. Although most were changed at 12-15K intervals, yearly. A KEY thing, then as now, is that little vial of "breaker cam grease" that used to come in ALL point sets, no matter what . . . until the factory electronic ignitions became popular. THAT was the key to longevity of the points and kept the gap where it needed to be. That grease is still around, just have to really hunt for it, sometimes.
The other issue FOR points is that there is no electronic box that has a minimum voltage (from the battery) requirement in order for it to fire the plugs. Which means that a point car will or can start if it'll barely turn over, as long as it will make a spark and there's enough air/fuel mix there for it to fire. A electronic box can raise that min battery voltage a good bit, such that it can turn over nicely and still not fire the plugs. Not unlike the "extended crank time" of a fuel injected vehicle with a weak fuel pump.
I still like that orig OEM Chrysler system, personally, but the HEI in my Camaro has been good too (as long as the modules don't fail for age). On the other hand, a good distributor with the breaker cam in good, non-worn peaks, condition that will still allow for the point gap and dwell to be in specs, with the breaker cam grease, PLUS some Iridium spark plugs, should be just fine, too, I suspect. EVEN if you drive as much now and you did back then.
Just some thoughts,
CBODY67
