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.
Basic inductive ignition boxes, such as Mallory's HyFire I, II, or III; Crane's HI-6S; and MSD's Blaster Ignition, take some load off the coil, do a better job managing dwell time and high current, and give the spark some extra punch. This typically translates into easier starts, smoother idling, and crisper throttle response.
More common are capacitive discharge ignition boxes with multiple-spark features. A CD box takes battery supply voltage, uses an internal transformer to step those 12 volts up to 500 volts or more, and stores that power in a capacitor. This voltage is stored at full strength so it's ready whenever the distributor sends a trigger signal. When boosted again through a matched performance coil, the resulting charge can be 30,000-45,000 volts riding the wires to your plugs throughout the entire rpm range. This hotter spark not only promotes quicker starts, a smoother idle, better throttle response, and fewer high-rpm misfires, but also lengthens point life (if you still have points). That's because the points now merely trigger the box, so they handle less current-typically less than 1 amp instead of 2-3 amps. Maintaining optimum point gap is also not as critical.
The multiple-spark feature found on most CD ignitions helps compensate for their one shortcoming: a shorter duration spark than inductive ignitions. This presents a problem primarily at lower rpm when the combustion process is slower and fuel mixture is typically richer. The solution is to fire the spark plug multiple times when the engine is below a certain rpm level-generally about 3,000-3,500 rpm. This is especially beneficial if your engine runs rough or rich at idle due to a lumpy cam or excessive carburetion--but we wouldn't know anything about that, now, would we?
The myriad ignition boxes available these days offer a wide range of other features like rev limiters and retard controls that allow timing adjustments in relation to supercharger/turbo boost or nitrous application. Most companies also offer digitally controlled ignition boxes and even PC-programmable boxes. You can do the research on what's best for you, but most street-oriented rods are well served with basic "6-Series" ignition boxes like MSD's 6A or 6AL, Crane's Hi-6, or Mallory's HyFire VI.
What's the point?"Hey, this is the 21st Century! What the heck am I doing fooling around with points?" Hey, we hear you and would like to stress that the upgrades we just discussed can do wonders for electronic ignitions, too. Meanwhile, let's talk about the many options for stoking your fire electronically.
Most domestic engines built since the mid-'70s, as well as most crate engines, came with electronic ignitions from the factory. GM's HEI distributor, with its integrated coil and easy one-wire hookup, has been a street rodding staple for decades. Likewise, Ford's Duraspark and TFI and Mopar's box-controlled electronic distributors are familiar to many rodders. They're all well suited for mild-milled rods and customs, and all can be easily upgraded with aftermarket coils, caps, modules, and control boxes.
Converting a breaker-point distributor to electronic operation is easier than you think thanks to the many available aftermarket kits. The Ignitor and Ignitor II conversion kits from Pertronix are very popular and can be had for a wide range of engines. Ignitor kits hook up with two wires, replacing the points with a Hall-effect-style pickup and reluctor wheel that work together to trigger the ignition. Crane's XR-i conversion for Fords and Chevys is even simpler-an electronic module replaces the points and uses the distributor's cam to create a trigger signal. It also has a built-in rev limiter. Mallory recently introduced a new E-Spark conversion as a lower-priced option to its long-running Unilite line. Like Unilites, E-Sparks use an optical trigger that's not speed sensitive (it doesn't need to reach a certain rpm to start triggering). Both are available for most Mallory distributors and a wide range of domestic points distributors.
Electronic ignition conversions are often used when you're updating an existing engine; those building new mills are more likely to buy aftermarket electronic distributors. What makes an aftermarket electronic distributor better than that junkyard find? For starters, you get an all-new part, one that hasn't endured millions of revolutions and sparks. Quality aftermarket distributors also feature sturdy new housings, fresh bushings-or, better yet, ball bearings-and smooth mechanical and vacuum advance mechanisms. Many aftermarket distributors are also more compact than OEM parts, especially compared to GM's bulky HEI. This can make a real difference on space-challenged hot rods.
Mallory's Mike Golding gives solid advice for assembling a new system: start with a quality, stand-alone electronic distributor and matched coil that don't require ignition box controls. You can always add a CD box, he says, but a stand-alone distributor will get you home should the box have problems and need to be unplugged on the road. Vacuum advance is another plus on the street. Good examples include Mallory's 42-Series Comp SS and 85-Series HEI distributors, MSD's Ready-to-Run line, and the Flame-Throwers from Pertronix. Surprisingly, such distributors are available for more mills than you'd expect. Mallory's Unilite and MSD's Ready-to-Run cover applications ranging from Y-block Fords and flatheads to early Hemis and Buick nailheads.
Just can't fight that urge to look racy? How about a fake magneto? Offered by both Vertex and Joe Hunt, magneto-look electronic distributors can be had for cool vintage mills like Hemis and nailheads, not to mention typical small-block Chevy and Ford fare. Internal coils and self-contained electronics make them look very convincing.
Charging OnWe've covered a lot of ground in a little space and there's still more we could add-the importance of quality plug wires, adequate charging systems, and multiple ground straps, for instance. Those topics will have to wait, but hopefully we've imparted enough advice to make you a smarter spark shopper. Naturally, the manufacturers' tech lines and Web sites are good resources for learning more about ignitions and specific products. We'd also recommend Todd Ryden's new book, How To Build High-Performance Ignition Systems, from CarTech. Armed with the right information, you'll have little problem giving your powerplant the shock that it needs.
