As a point of reference, MSD originally started in El Paso, TX in about 1974. It's major item was "multi-spark" ignition systems. Up to 20 sparks/firing impulse up to 3000rpms. At a time of the earlier emission controls, I figured that was a better way to get complete combustion and lower emissions, but no OEM apparently thought so. In the earlier "transistorized" 1960s, powerful Capacitive Discharge systems used the points to trigger big zaps each time the plug fired. With issues of ultimate power and length of the spark being what allegedly differentiated one system from another.
MSD came out with a line of new control boxes, going from the stock-oriented "5" and going upward from there. For the Chrysler electronic system, they had a "MSD-5C" which plugged into the Chrysler wiring harness. All exclusively with the multi-spark capabilities.
With success came other issues, including financial ones. Result, the brand was sold a few times. The first few sales probably kept a lot of the earlier engineers and such, but after that, when it was decided to "expand the line", that seems to be when things started to get flaky. Then, a few more sales past that to get us to where we are today.
This makes them NO better than anybody else, these days. Their old "core" multi-strike boxes might still be some of the originally-engineered items, but all of the later "non-multi-spark" items might be things made for them? I know MSD seems to take pride in their current "Made in the USA" orientation, but as those old enough to remember when everything was made in the USA, not everything made here was worth having over the long haul. Different price points and quality variations between brands. BTAIM
As these prior "name brand" lines have been purchased "by others", somewhat consolidated into existing product portfolios, a good bit of "the old stuff" has been and will continue to be lost, unfortunately (in one respect), as the market it used to play in has diminished with time. Look at how much of the old "Accel" is still around, for example. When I looked at the Holley carb website the other thing, LOTS of stuff (as to OEM-related carburetors) has been lost, replaced by "lines" of Holleys which seem to be about selling features FEW customers really know how to use or really need, by observation. Most with powerful-sounding "street fighter" names. Carbs which are more universal than not. In one respect, just because they have a particular name and the two national warehouses sell them, does not make them a good product.
What makes a good electronic distributor is the basic distributor (shaft, bushings, advance weights AND springs) plus good electronics inside of and hooked to it. Nothing magical about that, but some have more issues than others. Davis Unified Ignition (later DUI) took the concept of the GM HEI ignition and expanded it to other brands of engines. Pertronix went from small/niche to what it is today, some products with multi-strike capabilities.
Now that I'm remembering a few things about Paul's car, it could well be that somebody decided to remove the ELB system from it. Might not have put back a pre-ELB system in the process. Which would explain the Holley 4175 vac secondary spreadbore carb and the MSD distributor. Who knows what else might have been done? Just a suspicion. I DO remember that many of the ELB cars were de-converted haphazzardly by people who did not know what they were doing. Which made those cars very inexpensive on the used car market, while the body was still in good condition. So as "cheap cars" they got treated as such by many buyers who thought the "were getting a deal". Unless they knew how to fix what had been altered, to use a good carb and such, it was not a good deal and resulted in Chryslers getting a bad name as to reliability.
So, Paul, as an additional winter project, get a Chrysler factory service manual for a 1975 Chrysler so you can see what the non-ELB wiring harness looks like. Then compare that to what you have, PLUS what MSD says their distributor needs to have hooked to it. Plus the other items like the Ballast Resistor and such. This way, you will know what's there and what it needs to be. Might also look for the factory schematic for a 1978 Chrysler, when ELB evolved into "Electronic Spark Control" with timing control and no specific "lean" carburetor calibration.
ONE possible issue might be . . . does the existing MSD distributor have weights and springs in it for the advance mechanism or is it a "non-advance" distributor as the earlier ELB distributor would be?
Thanks for your time and consideration,
CBODY67
