When do I need an after market ignition system?

The short answer to this is; probably never. All of the aftermarket ignition companies claim you'll get more horsepower by using their ignition system. I hate to burst bubbles here but the fact is; numerous independent dyno studies, including my own, have shown no gain what so ever. This includes points type distributors as well. If your ignition is lighting the cylinders, then it's lighting the cylinders. If it's producing too weak of a spark, then you'll have misfire issues and you'll be dropping cylinders. Unless you have that problem, ie: dropping cylinders, misfiring at high RPMs, etc, then you don't "need" an aftermarket ignition system. 

Don't get me wrong. I like a lot of after market distributors and coils. They're better made because they're usually billet aluminum. They're more stable because they have things like ball bearings and better bushings inside to keep the inner workings more stable, and they're usually much easier to adjust and tune, such as re-curving the mechanical advance, etc. I've purposely installed hundreds and hundreds of them over the years, and my own blown and nitroused street car used them as well, but it's usually for the looks and maybe for the ease of re-curving, but almost never because I thought it was going to produce more power. Don't forget that most of the best magnetos on race engines use points. 

The object of the game is to ignite the cylinders. Once the cylinder is lit, it's lit. It either fires or it doesn't. You can't light it any more once it's been lit, and you can't re-light it once the spark has sparked. The ONLY time you need an elaborate ignition system is when running a seriously radical engine that has trouble igniting the cylinders because of very high compression and/or a very dense and wet air/fuel mixture, or one that has problems dropping cylinders under WOT situations. Until then, it's really not necessary.

I can't even begin to tell you how many racers and street buffs I know who have small fortunes invested in their ignition systems when GM's stock HEI system would have done the same job... if not better, and a hell of a lot cheaper. 

The biggest problem with aftermarket ignition systems, (other than they're really expensive), is that you can't check them yourself if you get a glitch or a problem because most of them convert the 12 volt power source to an extremely high voltage "square wave"... voltage that you cannot check with any standard volt / ohm meter. And when you have a glitch, or one needs fixing, you've got to send the whole thing back and wait 2 or 3 weeks for a reply from the manufacturer, which is almost always that there was nothing wrong with it and they blame your power supply wiring for "insufficient" or "dirty voltage" or some other lame excuse for why their box isn't working properly.

I can't tell you how many times I've had a glitch in a client's expensive ignition box, so I remove it and installed a second one and the glitch goes away, so I send the defective box back to the manufacturer only to be told there was nothing wrong with it. So I get it back in the mail 3 weeks later, re-install it and instantly have the exact same glitch again. Then I remove it again and replace it with the one that worked, and the glitch is gone again, which proves it's something with that one box that not even the manufacturer can find, or will admit to. I've literally run into this dozens of times over the decades and kept a couple of new units on my shelf so I could switch them out and see if the glitch is in the box or not, and 99% of the time, it is. 

NASCAR uses 2 boxes with a switch on the dash that changes from one box to the other... not "if" the 1st box fails, but "when" the 1st first box fails. This way they can switch to the 2nd box mid-race and continue racing. Now think about that... if they were so reliable, why would NASCAR run 2 boxes with a switch to go from one to the other? 

Ford probably had the worst stock (electronic) ignitions systems. Their factory modules stank. They had the least amount of dwell time and the most expensive price.

Chrysler had a great ignition module that saturated the heck out of the coil causing a big spark. A neat, inexpensive trick to do back in the day was to use a Chrysler module on your Ford engine. It really woke-up the spark. It's a cheap & easy swap because all a module needs is a signal from the magnetic pickup, and Ford, GM, Chrysler, and even the vast majority of the aftermarket distributors, all use magnetic pickups. 

The cool thing with running an HEI distributor or a stock Ford distributor using a Chrysler module is that you can get any of the parts at any local auto parts store, and they're cheap, so if you want to just check something by replacing it, (the module, pick-up, etc.), you can without having to wait 2 or 3 weeks for shipping and wasting several hundred dollars.

This is especially true for you performance boat guys and gals. If you're up at the lake and you have a distributor problem, like someone leaned on the engine and cracked your cap, or the module burned out, or whatever, if it's some elaborate aftermarket system, your weekend is done because there aren't really any speed shops around anymore who stock replacement parts, but you wanna know a secret where a bunch of replacement parts are at if you're running an HEI or other stock distributor or ignition set-up? THE PARKING LOT! You'll find a number of "donor vehicles" that you can borrow a distributor cap, a coil, a plug wire or two, or a module from in the parking lot and your weekend is saved! I can almost guarantee you though that with an MSD or other fancy distributor or control box, you won't find a single donor vehicle in the parking lot that you can borrow something from. It's definitely something to consider if you're running a boat, especially if you go to lakes and rivers far away from any big cities that might have a store that carries the part(s) you need. 

So if you're interested in running a Chrysler module on your stock Ford distributor, here's an image of a simple wiring diagram for it. You can enlarge the image by clicking on it. The plug for the module you can buy at pretty much any local auto parts store. 

And as far as Chevy HEI distributors go, I can't tell you how many people say you can't run an HEI distributor on a high performance engine because they "sputter" after 6,000 RPM. Say that to our old Super Gasser that ran 9.60's all day long and went through the lights at 8,000 RPM without a glitch. After far too many glitches, sputters and high RPM oddities, I took the MSD 7AL2 box, billet distributor and funky coil that we had on it and tossed them into the trash because I got sick and tired of them causing all of the strange things they were causing and dropping cylinders when the car came-off the trans brake at 5,000 RPM.

Keep in mind, for those who don't believe an HEI can handle high RPMs and more serious engines... it's the same type of magnetic pick-up that's inside the high-end aftermarket distributors, and the 4 pin module inside is the very same one that some of the high dollar ignition brands used in their billet "race" distributors. At the race track, I had all kinds of people come-up and say to me; "Hey, you can't run an HEI distributor in an engine like that at those RPM's.", after they just watched the car go down the track and run a 9.60 et at 8,000 RPM without a glitch. Seriously, you can't make this stuff up. People would rather believe old wives tales than what they just watched happen right in front of their eyes. And when I would ask them what the difference was between an HEI's magnetic pick-up and 4 pin module compared to the magnetic pick-up and 4 pin module inside their cool looking billet distributor, they could never give me a straight answer. You don't need to spend a bunch of money on an elaborate ignition system when running a mild to mid-range performance or race engine. 

I've built all kinds of street cars that ran 10s, 11s and 12s, and race cars that ran well into the 9s running HEI distributors and stock Ford distributors using Chrysler modules, and when you hear one of those engines wound upwards of 7,000 - 8,000 RPM without a sputter, you'll be a believer. As the old saying goes... "simplicity is bliss" :-) 

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