Big cams are fun and lots o' carbs are neat, but you've gotta light that fire to blast down the street. What do you say we spend some time talking about that unsung engine system, the ignition?
Our focus here is on ignition improvements and the many choices available for lighting your mill's fire. We'll put extra emphasis on upgrades for vintage engines since they're a little trickier to shop for than the average small-block Chevy. Thankfully, more new products are being made all the time.
The BasicsSeasoned R&C readers likely remember the rite of passage of learning to change breaker points and adjust dwell and point gap. Part of the lesson was learning each ignition part's function-that the coil takes low-voltage, high-current battery power and creates a low-current, high-voltage charge; that the coil works with the distributor to send sparks to the plugs and light off the air/fuel mixture; that breaker points are-or were-used to trigger the whole process.
Breaker points act as the system's switch. When closed, they provide a path to ground for the battery voltage, keeping low-voltage juice flowing through the coil's primary wires. The current flow is broken when the points open, causing the coil's magnetic field to collapse and transfer the charge to the secondary windings, where those 12 volts are stepped up to 15,000 volts or more. This high-charge spark is shot out of the coil's secondary tower back to the distributor, where it's routed to the appropriate plug wire.
It's an adequate system, but it has limitations. Points require regular adjustment and wear quickly due to continuous physical contact. They also tend to limit rpm capability and are less powerful than the electronic ignitions that have been with us since the '70s. OEM-style electronic ignitions generally use magnetic triggers instead of points, so there's no physical wear and less rpm limitation. Electronic ignitions are also more powerful, accurate, and consistent than points. We'll talk more about that in a minute.
Easy UpgradesDespite electronic advantages, many rodders still run points distributors for tradition, economics, or because an electronic substitute is not readily available. That's fine as long as everything is in good shape and in tune. In fact, there are several ways to improve a points distributor and take advantage of more modern technology. Most such mods also work great on electronic ignitions.
Adding a performance coil is a simple upgrade and a good foundation for future improvements. Performance coils produce a higher-voltage spark, which alone can improve starting and idle characteristics. They'll also handle the higher voltage and current generated by performance ignitions. You'll be amazed how many coil options there are, so be sure to do your research, ask questions, and choose a coil that's compatible with any ignition changes you're planning. Getting a coil and distributor from the same manufacturer is generally a good idea. You may also need to add a new or additional ballast resister to match your coil of choice.
Another easy upgrade is installing an ignition control box like those available from MSD, Crane, Mallory, Accel, Pertronix, and others. These come in a wide range of configurations and degrees of sophistication, but most will work with any distributor-based, 12-volt, negative-ground ignition. Just what do these mysterious boxes do? That depends whether they're inductive discharge controls or capacitive discharge (CD) boxes.
Most OEM ignitions are inductive discharge systems. The coil carries the heaviest burden as it takes in battery power, stores it, boosts the voltage, and releases it thousands of times a minute. Remember dwell? That's the time the coil takes to transform low-voltage battery power to a high-voltage charge. There's plenty of dwell time at lower rpm, but as you bring the revs up, the coil may struggle to consistently produce a full charge. Misfiring and power loss are potential results.