Basic Musclecar Ignition System Upgrades

The know-it-all car guy was leaning back against a vintage Chevy, cigarettes rolled up in his t-shirt sleeve, dispensing automotive advice like a change machine. “Nah… any spark will do to run an engine,” he said, as his loyal subjects soaked it all in. “As long as you get fire, it will run,” he continued as his listeners oooh’d and ahhh’d at every word he spoke.

A mechanical ignition system cannot measure up with an electronic ignition system. – Terry Johnson, Crane Cams

We’ve all seen the neighborhood know-it-all car guy that seems to know everything about cars – ALL cars – even cars that are so secret that only a handful of government agents know about them.

Of course we are being a little sarcastic here but when it comes to ignition systems, there are a lot of terms and a lot of slick marketing ads that can make selecting the right ignition upgrade confusing. Listening to the local back yard pro can make things even worse. So we decided to talk to some ignition experts and make a guide to basic ignition system upgrades for classic musclecars.

Starting with the most basic upgrade to a complete system upgrade, we talked to ignition experts from Crane Cams, Mallory, MSD Performance, and Performance Distributors, to get the scoop on what every musclecar enthusiast should know about ignition systems.

It Depends…

When we posed the question to Mallory’s Racing Services Manager Graham Fordyce, we asked what ignition upgrade should every musclecar guy perform? Fordyce responded by saying, “It depends.” According to Fordyce, “It depends on what the enthusiast is starting with. It’s going to depend largely on what he is trying to do with what he has.” We considered this a whole view approach to the subject.

Steve Davis, President of Performance Distributors, prefers to look at things by the numbers. “We base our recommendations on the customer’s rpm level, not their horsepower level,” said Davis. “Our DUI distributors are offered in two versions. A street/strip version that fires to 7,000 rpm and a racing version that fires to 10,000 rpm.”

Steve Davis of Performance Distributors makes upgrade recommendations based on rpm level. Leave the horsepower out of the equation for a basic musclecar upgrade.

MSD’s Product Manager Silver Gomez was also reserved with his response as he offered yet another facet to look at when deciding to upgrade your ignition system. “It depends on the engine itself. If it is a new engine platform or if it has been recently rebuilt, you will probably want to start with an ignition box upgrade. If you start with something that is already built and has a lot of miles on it, you may want to consider a distributor or different ignition box, depending on the application.”

If your engine has a lot of hard miles on it, like the one pictured, a new distributor or other major components may be the best option.

It is easy to see based on the variety of responses from our experts that choosing an ignition system upgrade requires some thought. There are different aspects to consider, like what is the vehicle going to be used for? What condition is the engine in? What rpm range do you need to cover?

First Things, First

According to Graham Fordyce, “The first thing you want to do is get a good trigger, which would be your distributor. The second thing that you would want to look at is wires. Then upgrade the coil and finally the ignition box.”

If your stock distributor gears or stack up is worn, the signal will not be as precise and the whole distributor should be exchanged for a new digital electronic ignition version.

Fordyce explained the thought process behind upgrading a musclecar’s ignition system, “If you have a pre-’74 car with a points type distributor, there is a huge advantage in switching over to an electronic ignition system.”

MSD’s Gomez agreed, “An electronic ignition will really wake an engine up. It’s going to get better gas mileage, burn the air/fuel mixture better and if you have some oil blow-by, it’s going to burn that as well. You will need to keep an eye on your spark plugs though, to make sure they don’t get oil fouled.” 

A stock distributor with worn parts, like the distributor on the left, should be replaced with a modern unit designed for your application, like the distributor on the right.

 “Obviously with a vehicle of that age, the bushings in the distributor are probably worn out so you will probably want to spend the money on a new distributor anyway,” Fordyce added. “A basic musclecar upgrade for a daily driver street car should be a distributor. The original distributor’s springs and weights, mechanical advance is probably worn, the bushings are probably worn and this will cause the rotor to fluctuate. It’s probably best to spend the money and buy a whole distributor.”

Crane Cams’ Product Manager Terry Johnson explained why their digital module was a great basic ignition upgrade. “In a distributor, a worn mechanical stack-up is going to add to timing and any bouncing around of the signal. Any time that you have mechanical differences like that because of wear, it’s not good. The good thing about our module is that we actually use a Mil-Spec pickup, which is way overkill for that, so if the distributor is worn or the bushings are worn, the pickup gets it’s signal through the distributor cam lobe so no matter how far it is away, it’s still a sufficient signal for the unit,” he said.

Like most contact points or HEI module conversion kits, MSD’s HEI Heat is a simple replacement swap that is not visible on the outside of the distributor. This is desirable to the enthusiast that wants to keep his engine looking stock but wants to take advantage of performance upgrades.

MSD’s Gomez said, “The HEI module with an HEI distributor is the ultimate when you are going for the original look. For the guy that is a die hard original look but wants hotter spark and more energy, the HEI Heat is made for them.”

Steve Davis explained the benefits of electronic ignitions over points style ignitions by saying, “You can get more voltage at your plugs because no ballast resistor is necessary with electronic ignition systems. That ballast resistor is required in breaker point distributors to prevent the points from burning up. This usually reduces the voltage at the plugs to nine or ten volts,” he clarified.

Performance Distributor’s Steve Davis explained that electronic ignition modules bring more voltage to the spark plugs because a ballast resistor is not needed in this setup.

In addition to the higher voltage, Davis pointed out that there was a maintenance benefit. “Electronic ignitions are maintenance free compare to point style ignitions. You don’t have to worry about adjusting or changing your contact points,” he said.

“The advantages are enormous. You don’t have the wear and tear of parts that you have to maintain. The inaccuracies and the maintenance of that type of mechanical system cannot measure up with an electronic ignition system like our digital conversion module,” said Crane Cam’s Johnson. “The draw on the system is extremely low so that’s not a concern what so ever. It will run all the way down to 7 volts battery power so even in a discharge situation you still have ignition. As long as you don’t put on add-ons that take up in compression to 14:1, there is plenty of output. At that point you will truly need add-on ignition system stuff.”

Replacement ignition modules can take an old distributor and turn it into a system that will really wake an engine up.

Enthusiasts have long realized that there is less maintenance with an electronic ignition and the vehicle becomes more efficient because the engine does not need as much fuel to start and to accelerate. Not only does this help reduce gas costs but the reduced exhaust also creates a more environmentally-friendly car and one with a better chance of passing a smog test. The conversion is a simple one that takes less than 15-minutes by a trained technician and will probably cost less than $300. It is simple enough to do yourself if you have some mechanical ability, and it will cost significantly less.

Bone stock Chevy musclecars made after 1974 came with GM’s HEI distributors. The advantage of having the coil in the distributor was quickly recognized. Modern technology has added to this style of distributor, making it a street/strip performance component. Almost every ignition company has their own version of the HEI distributor.

HEI Distributors

“For vehicles that are 74 and later, they came with HEI distributors,” explained Fordyce. “At this point you are looking at whether or not to use something similar to the OE distributor. Most ignition companies have an HEI distributor in their lineup. You don’t want the cheap one. You want an HEI distributor that has a good housing, a machined gear, not a cast one but a machined gear, a strong cap – those are the things that help determine the quality of the distributor,” he added.

“When it comes to the drive gear, some materials are not going to work,” stated Johnson, “Like steel on steel with your cam gear. You could have catastrophic failure if you don’t have a properly matched gear.”

MSD’s Gomez explained the HEI’s popularity. “The Chevrolet HEI distributor is a favorite for musclecars, street rods and even circle track racers because the integrated coil keeps under hood wiring clean and the idea of running one wire to the distributor keeps things simple.”

The differences between an HEI distributor and a non-HEI distributor are very noticeable in most cases.

About Davis Performance Distributor’s D.U.I. units, he had this to say: “A lot of today’s aftermarket EFI systems are compatible with our D.U.I. distributors. The advantages of the D.U.I. distributor being a nice one-piece ignition and reduced wiring.”

Non-HEI Distributors

Mallory’s Graham Fordyce proclaimed his selection criteria in distributors by saying, “Depending on what RPM you are trying to achieve, distributor selection is more personal preference because they all function pretty well at higher RPM. The Unilite is dead-on accurate as far as timing. Then you have the magnetic breaker less ignition, which is a stand alone ignition that will run without an ignition box – all it needs is a coil. When you get to an extremely high RPM, magnetic pickups tend to retard the timing more degrees at high RPM. A lot of drag racers actually like that because if you pull a couple of degrees out at higher RPM you gain a couple of miles-per-hour.”

Distributor selection can come down to personal preference in the options that are available according to Mallory’s Graham Fordyce. This Mallory distributor offers two magnetic pick-ups, and adjustable collar, and a choice of gear drives.

“Something like the Mallory Unilite distributor is a great upgrade for your basic streetcar,” adds Fordyce. “It’s very simple to install. If you are upgrading from a points type ignition, you typically have the right amount of voltage going to the coil for that distributor. It only takes three wires to hook up.”

Choose a well built distributor advised Crane Cam’s Terry Johnson.

When it came to choosing a distributor, Crane’s Johnson advised, “Choose a well-built distributor and one that doesn’t have a lot of end play in the unit. It’s very easy to over-buy but it’s even easier to under-buy that part. Everybody sees a $99 item and thinks that is going to work, but on their third one it begins to make sense that they should have bought a good distributor to begin with.”

According to Gomez (MSD Performance), “Our distributors have the ability to change the timing curve easily, which the original OE distributors don’t have. Those parts are included in a parts bag in the box with our distributors. It’s as simple as taking the cap and rotor off, then making a spring change. You can change the total timing by changing the bushing. That can get a little more complicated but it is pretty much simple math that you have to do. A lot of the camshafts tell you what you should be running as far as timing and total timing and that’s where you should be at.”

Upgrading Your Coil

According to all the experts, converting to electronic ignition is the most logical first step. After that it becomes a matter of aiming for efficiency in your system for power and a complete burn. “After you have updated your distributor to electronic, you need to look at coils,” said Fordyce. “With coils the thing you really need to look at is your camshaft. A coil that is designed for a racing application is going to have a really fast rise time, which is going to move the output RPM up. So it will work really well at higher RPM but not so good at idle. Like choosing a camshaft, you need to have a coil that is operating in the right rpm range for what you are going to do. A race part used on the street will often run horrible. You have to get the right part for the RPM range.”

Choosing an ignition coil for the RPM that your engine will be operating in is critical. Using a racing part designed for 7,000 rpm in a street car that only sees action from one red light to the next red light is not only inefficient but it won’t perform well.

When selecting coils, Fordyce advises, “The things that damage coils is ambient temperature, the internal temperture and how you cool that. The internal temperature is based largely on RPM. As the engine speed increases, the coil is going to have to work harder and generates more heat. If the coil overheats because you’ve chosen the wrong coil, the coil will be more prone to fail. There are several different types of windings to resolve those types of issues. The turn ratio in the windings tells you what it is. The lower the turns ratio, the more street able that coil is going to be. There are a lot of things that go into it but that is one of the quickest ways to figure out which coil is best for the RPM range.”

Most of the ignition companies also offer a stock-looking oil canister style coil that has beefed up internals. If you are looking for an OE-like appearance with some real power behind it, this is the way to go.

MSD Performance still prefers to add the multiple spark to musclecars with one of their ignition boxes but Gomez explained why ignition coils are an important consideration. “You’re still going to want to mount the MSD ignition box but you are also going to upgrade the coil. The coil is what actually creates the secondary spark that burns the air/fuel mixture,” said Gomez, “So not only will the MSD box help with the multiple spark below 3,000 rpm, the coil itself will give you the current which is the intensity of the spark. That intensity is what is going to burn that air/fuel mixture. Of course, the hotter the spark the better the burn – so you will want to upgrade the coil. We offer everything from a canister style coil as high as the HVC II coil which is considered a high voltage current coil. We have a first generation and a second generation.”

Gomez also warned, “You have to consider how much more you are going to throw at it. If you add more fuel you might be adding more compression or you might be adding different heads or something like that, then that is where you really want to throw in a performance coil with the MSD box.”

Aftermarket ignition coils can be mounted almost anywhere and many times they add to the under hood look of the car.

Ignition Boxes

When we asked our experts about upgrading to an ignition box, they all answered with the same question. “What are you trying to do? What are you trying to accomplish? Is it a street driven car that you take out on Friday and Saturday nights to cruise around with your buddies or is this something that you are occasionally going to take to the track?”

When it comes to ignition boxes, the differences can be huge, even ignition boxes within the same company.

Fordyce got right to the point, “You want the box to be digital. In some classes of racing they still require an analog box. What you want to look at is a digital box for anything on the street because they are a lot more precise. The components of the digital box are smaller, lighter and tend to be more robust. The next thing you should look at is features and benefits that pertain to the type of driving that you intend on doing. If you have a big compression type motor, you will want something that has a start retard so that the engine will start easier without kicking back against the starter.”

“Digital signal is far more accurate. There’s no doubt about that,” said Johnson. “You are able to meter what you are doing there versus an analog. The other side of that is digital systems are way more prone to electrical interference. So if you don’t have good harnessing in the car, it could lead to issues in the system.”

Gomez had some extra advice, “When you start increasing cylinder pressure by adding boost, or getting to extreme cylinder pressures, you will still have the same amount of current because you have the same voltage at the spark plug. The rule of thumb is, the higher the cylinder pressure, the lower the spark plug gap you need to go with. That depends on the amount of pressure you have. Under so much pressure, you need to have voltage to be able to jump the gap 25,000 volts to 45,000 volts.”

An ignition box that will perform with the other ignition system components within your vehicle’s primary operating range is the best choice. Almost everyone agrees that a digital signal is a good choice for musclecars.

For a street musclecar guy, he probably has a 10:1 compression ratio or less, probably a small-block Chevy, nothing too exotic, naturally aspirated, we have a standard MSD ignition box and a standard coil. If they want to keep their look orginal, we have an MSD box and a standard canister style coil that they can use to keep it looking original. Then we even have a billet distributor that they can use with it and that is pretty much the whole ignition system,” he added. “For the guys that want more performance up to about 6,000 to 7,000 rpm, or the guys that want to go to the drags trip on Saturday night, that is where the MSD-6AL comes in. Add in a coil and distributor on that and you have a winning combination.”


Our experts universally agree that changing to an electronic ignition is critical for a basic musclecar upgrade. Starting with upgrading the trigger, either changing the module in the distributor or the entire distributor, then upgrading the coil for the desired rpm range. After that an ignition box for more energy can be added to complete the system.

A basic ignition upgrade is very affordable and can be completed in a relatively short time. The results are well worth the investment in time and money for the everyday musclecar enthusiast.

Paying attention to the small things ends up being the best money spent on ignition upgrades. Look for a digital signal, quality components, and don’t skimp on false economy. Buying a module for a worn out distributor will probably not help, but switching to electronic ignition is a necessity, so purchasing a new digital electronic distributor with the correct drive gear is a smart buy. Each case is a little different but these tips and words of wisdom from the experts should help you decide on what upgrade is right for you.



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About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
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