Carb to EFI: Other ignition control alternatives

Objective of this Article

In Part 2 of this article, we covered how to take control over the ignition on our 1977 Chevy Nova. We opted to get a HEI distributor out of a van in the local junkyard. This is a pretty straightforward option if you’ve got a Chevy V8. But what if you have a different brand of engine? There are quite a few different ways to get the benefits of computer controlled ignition. This article will give you an overview of what options are out there that you can pick from.

As always, we highly recommend you dig into the MegaManual in addition to these articles.  It’s a big read, but it’s an invaluable resource that our guides are meant to supplement and not replace.

Using the distributor you already have

The biggest problem with using the stock distributor on a carbureted car (unless your car had a computer controlled ignition and a carb; rare but it exists) is that its advance mechanism will move around, making the advance table into something more like a trim table. You also have to deal with any potential slop in the advance mechanism. While you can simply disconnect the vacuum advance, removing the mechanical advance is a bit more work on a stock distributor. Exactly what this involves will depend on the distributor; this may be simply bolting two parts together or it may mean welding the shaft.

If you have aftermarket ignition mods on your car, you may want to keep them even with the Megasquirt in control of the spark. MSD’s Pro-Billet distributors usually have a method built in for locking out their advance mechanism. If you’re using one of these, follow this link for instructions on how to use the MSD Pro-Billet distributor with Megasquirt. This also applies if you are using a Flying Magnet crank trigger or similar setup.

Using factory ignitions

The first choice for many MegaSquirt owners is to follow the same approach we did and retrofit a locked out distributor from a later engine. While our article covered what to do on a small block Chevy, Ford and Mopar owners can also benefit from the factory engineering. So can many imports.

If you have a small block Ford, a 460, some of their V6s, or even a carbed 2.3 Pinto engine, you can swap over a TFI distributor off a later fuel injected models. Use the ignition mods in our guide to installing MegaSquirt on a 5.0 Mustang to get your ignition up and running.

Chrysler’s Lean Burn distributor can give the same benefits to Mopars. While some of the hardware has a bad reputation, the distributor itself is a solid part and available for big blocks, small blocks, and even slant sixes. Follow this link to see how to use the Megasquirt with the Lean Burn distributor.

If you’re converting a Datsun Z car, you can use the ’82-’83 280ZX Turbo distributor. We also have articles on the Hall effect distributors used on Volvos and water cooled VWs, which also come in handy for carb to EFI conversions.

Using a crank trigger

Another option is to go with a missing tooth type crank trigger. These can be used either with or without a distributor. Compared to the pickup in a distributor, a crank trigger will be more accurate as it does not have to deal with timing chain stretch, and the Megasquirt-II can take advantage of the extra resolution you would get from a 36 tooth wheel. The Megasquirt can work with many different missing tooth wheels, but the most common option is a 36-1 wheel. We have a series of articles on how to install 36-1 crank trigger wheels and configure the MegaSquirt for them.

Crank Trigger Wheel Installed
Crank Trigger Wheel Installed