Electronic ignition for Slant 6

My car, being a 1965, had points when I bought it in 1983. In 1987, I upgraded to an electronic ignition from a 72 Scamp mainly because I was getting tired of pulling the distributor to do a tuneup and I had a free parts car. The Mopar EI system was mostly trouble-free except for a couple of ECUs that burned out on me over the years. The ballast resistors never gave me any trouble. Also in 1987, I also upgraded from a Carter BBS to a 9625 AFB and ran that until 2004, at which time I upgraded to a Quadrajet (using the OEM tuning from its 77 Pontiac donor car). See Quadrajet Upgrade.

It wasn't until 2017 did I get around to tuning my Quadrajet and got set up with great power and fuel economy. The AFB had better fuel economy than the BBS and the Quadrajet was better than the AFB. I often take long road trips (easily hundreds of miles per day) so fuel economy is important to me. The nice thing about my Quadrajet is that it has an adjustable part throttle fuel mixture and I found that it got a lean surge around 3.5 turns from the bottom. A lean surge comes from the ignition system not being able to reliably ignite a lean fuel mixture. Having read up on the GM 4-pin HEI upgrade, I thought this would allow me to get a hotter spark so as to be able to run leaner highway fuel mixtures. See Quadrajet Tuning.

I did HEI Ignition System Upgrade in 2018 and found that the HEI system does in fact have a much hotter spark than the Mopar EI system. It has no problem allowing me to fully lean-out my part-throttle fuel mixture by turning the APT all the way in (ie, 0 turns from the bottom) with no lean surge. I haven't driven my car much last year so wasn't able to do more carb tuning lately.

If your existing points ignition system has no trouble igniting your fuel mixture within your normal RPM range, you are not going to see any real performance improvement by upgrading to an electronic system (Mopar EI, Pertronix, HEI, etc). Its only when you start pushing the limits of the ignition will you start to see a benefit.