Zap It!

We have been talking about ignitions and distributors quite a bit lately, since their workings are so critical to a car’s performance. A properly operating ignition system can make or break a classic, as all of the events must occur at the precise moment.

Even though these components are often sealed in boxes or hidden under distributor caps, the process of getting a spark to each cylinder isn’t too complicated. The ignition system is made up of a coil, distributor, plug wires and spark plugs. Each part has a specific job and helps move the electricity to its final destination.

At the beginning of the system, the coil converts low voltage to high voltage to make a spark. This spark then passes through the distributor, which has been charged with three tasks: It has the switching mechanism that tells the coil when to make sparks; it has an advance mechanism to vary the time when the switching/spark occurs; and its rotor and cap tell the spark which cylinder to fire. The plug wires connect the distributor to the plugs, and the plugs handle firing the spark in the combustion chamber.

While we have been focusing on stock ignition systems, now it’s time to talk about upgrades. Distributors and ignition systems have improved greatly since many of our cars were built and thanks to a strong aftermarket, many products are available to upgrade our cars.

Shaving Points

The Crane XR700 is a universal-fit electronic conversion that has been around for many years; it’s proved itself as a flexible, reliable system.

The points found inside the distributor on many classics are a very simple and fairly durable switching mechanism, but most of the electronic ignition conversions on the market these days can help bring an increased level of performance and reliability to our cars.

Myriad options exist for more common cars, especially common British models from MG, Triumph and Jaguar (and those less common that use the ubiquitous Lucas distributors). Even if there isn’t a direct-fit example for your car, there are many universal-fit ignition conversions that can bring just about any car’s ignition into the electronic age.

If all you want to do is eliminate your points, two good options are the Ignitor (or Ignitor II) conversions from PerTronix and the XR700 from Crane. While both are good systems, we’ve been bigger fans of the Ignitors through the years. These simple-to-install systems are specifically matched to your distributor in kit form and have a simple, two-wire hookup. Further, they have no external control units, maintaining the engine bay’s original look.

The Crane systems feature an external control unit and universal installation components, making them more flexible and able to fit a wider variety of vehicles. While they don’t offer quite as much simplicity as the Ignitor, they are a good choice for less common cars that don’t have direct-fit kits available. RML Automotive offers conversions to use the Crane trigger on many distributors.

Dyno testing on MGBs has shown us that either ignition conversion is usually worth 2 to 3 horsepower at the wheels on basically stock engines. Street prices for the Ignitors are usually $80 to $100, while the Cranes are usually about $30 more.

CDs May Be for You

PerTronix Ignitor systems are direct-fit and specific to most applications. They’re easy to install internally, plus a simple two-wire hookup with no external control box makes them a great option.

If you want to get more sophisticated with your ignition, we’d recommend that you look into a multiple spark capacitance discharge system from a supplier like MSD or PerTronix. These externally mounted units feature a large capacitor that charges the coil quicker and much more effectively than is possible by just the coil. The result is a much stronger spark.

These boxes also offer multiple sparks per ignition event, which can help burn part of the air/fuel mixture that was “missed” during the first spark.

We have used MSD’s 6A and 6AL ignitions for years and have found that they offer a slight power gain and noticeable drivability improvements. The MSD receives its marching orders from the distributor (points or electronic) and enhances the ignition with very powerful sparks throughout the engine operating range—multiple sparks are used below 3000 rpm.

The PerTronix Second Strike is similar to the MSD, except that it limits itself to two sparks per firing event. However, it does this throughout the operating range of the engine. It offers gains in power and drivability just as the MSD unit does.

Additionally, the PerTronix offers a built-in adjustable rev limiter that allows adjustment from 1000 rpm to 9000 rpm in 100 rpm increments. The MSD 6A does not have a rev limiter, but the 6AL does. Instead of a dial adjustment like the PerTronix unit, the MSD requires the use of plug-in modules. Street prices for the MSD 6A are usually $180 to $200, and the 6AL is about $30 more; the PerTronix Second Strike usually retails for about $300.

Better Distribution

The Mallory dual-point distributor is well built and fully adjustable--a great option if you want to replace your stock distributor with something a little more advanced.

While these upgrades are fine for most applications, you may want to replace your distributor altogether. If you have a worn-out distributor or one with an advance curve derived for emissions reasons, an electronic conversion or a capacitance discharge upgrade won’t be overly effective by itself—you will need to address distributor wear and have a proper advance curve as well.

The easiest option for British cars is probably to buy a new Lucas 41427 45D4 distributor. While there have been a few quality control issues with these units in the past few years, they seem to have been resolved and these distributors offer quality, a good advance curve, and readily available repair components. This is a direct-fit for most four-cylinder British cars, and street prices for these units fluctuate between $200 and $250.

The only trouble with the Lucas distributor is that it is points-based. So if you want electronic ignition, you will need to remove the points and install an Ignitor, XR700 or other electronic conversion yourself.

Another long-standing option is the Mallory dual-point distributor. Available for four-, six- and eight-cylinder cars, this universal-fit distributor is a very well-built unit and completely adjustable. Kits are available to modify its advance curve; even the vacuum advance, when so equipped, can be adjusted.

The downside to these is that they come with no drive dog, which means you must remove one from a used distributor and mount it. It’s also usually necessary to drill an accurate hole in the distributor shaft and pin the dog in place.

As the name implies, these distributors use two sets of points to improve spark quality. While they’re a little tricky to set up, they do offer long points life. As with the Lucas distributors, electronic conversions are available to eliminate the points altogether. Street prices for the Mallory distributor are usually around $150 to $250, depending on application. (The V8 units are less expensive.)

One unique ignition option we recently tested is the D.U.I. distributor sourced from Performance Distributors. Currently available for the MGA and MGB, this distributor is a GM HEI unit modified to fit in place of the factory Lucas unit. Due to its large size, however, it’s a tight fit in the engine compartment and it’s a bit pricey at $399. Nevertheless, if you have a worn-out distributor and want to convert to electronic ignition, you could spend this much—or more—with other options. Plus the D.U.I. lets you do it all at once.

Dyno testing on an MGB showed increases in power and drivability that were similar to other electronic systems. This unit is especially well suited to those of you who may like to play with advance curves, since there is a wide availability of advance curve kits available for HEI distributors. It may also fit other four-cylinder British cars that came with a Lucas distributor as long as there is enough room in the engine compartment for the D.U.I. distributor.

Other Go-Fast Bits?

What about coils and plug wires? Will upgraded equipment here make more power?

Honestly, we’ve never tested a “performance” coil that outperformed a stock coil that was in good condition. The same thing is true for plug wires. On the other hand, we have found that faulty coils or plug wires can cost a lot of power.

So our advice is to ensure your coil and plug wires are in excellent condition before you invest in “performance” items. If you’re going to replace the stock units, there is no reason not to go to the performance items, but don’t expect any miracles as a result.

Parting Thoughts

Before we wrap things up and send you to check out the many sidebars that accompany this piece, we have a few final notes about many of these electronic conversions.

Electronic systems often require a fair amount more electrical current than stock systems, which may tax your charging system. If your charging system cannot keep up because you have a powerful radio or other electronic accessories, you’ll find that your ignition system will struggle as well.

Additionally, we have found that rotors on the Lucas 25D-series distributors are more likely to fail unpredictably when they are teamed with a higher-powered ignition, so we always carry a spare. Finally, there seems to have been a bad batch of Mallory condensers, so we carry a spare in all our cars that are running their dual-point distributors.

We’ve only scratched the surface regarding ignition upgrades for our classics, but these points should get you heading in the right direction. While we tested the more popular setups, there are other choices out there ranging from other electronic conversions to distributorless systems to computer-controlled advance curves.

As we test these setups in the future, we’ll be sure to share our results. In the meantime, you can see that there are plenty of good, tested options to choose from now.

Sample Installation: MGB With Ignitor

We’ve been installing PerTronix Ignitors on MGBs for years, and have found them to be one of the best and easiest upgrades possible for this car. While the Ignitor can be installed with the distributor still in the car, we always remove the distributor to make the job easier.

Once the unit is on the bench, we remove the rotor, electrical low tension (LT) lead, points and condenser. A magnetic slip ring is then installed on the points cam, with the electronic sensor replacing the points. A provided gapping gauge is then used to make sure the sensor is properly positioned.

The wires are routed from the relief in the distributor body where the electrical low tension lead used to reside and through a rubber grommet. We always tightly attach a small wire tie on either side of the rubber grommet to ensure that the wiring doesn’t get pulled too tight in the future and cause damage.

Next we reinstall the distributor and set the timing. That finishes the installation. (Note: We have gotten a lot of phone calls and e-mails from people through the years who don’t realize that the timing needs to be reset after an Ignitor installation).

Once the installation is complete, we put the points, condenser, LT lead and screws into a plastic bag that is then stored in the glove box. We also throw in a spare rotor. While we’ve rarely seen Ignitors fail, a little spare parts kit is handy if you’re ever on a long trip. As we mentioned, Lucas 25D distributor rotor failures seem to be exacerbated by a high-powered ignition, so we always carry a spare.

We have dyno tested several MGBs and MGAs that have received the Ignitor upgrade, and it almost always adds 2 to 3 horsepower at the wheels while also improving starting and drivability. Looking at the dyno graph, you can see not only the power increase from the Ignitor, but that the line is smoother, indicating better drivability.

Sample Installation: MGB With Ignitor and MSD 6A or PerTronix Second Strike

Here is the MSD 6A installed in an MGB. The unit comes with ample wiring to install in any dry, well-ventilated location. We usually mount them on the inner fender well.

If we have a bigger budget to work with, we’ll install an MSD 6A (or 6AL) or PerTronix Second Strike system along with an Ignitor. These systems make starting easier still and reduce the amount of time the choke is needed during warm-up. While these units don’t add much more power, they make a very noticeable difference in drivability because an engine equipped with one of them runs much more smoothly.

Each system uses a five or more wire hookup, depending on the specific car and system used. In each case, they need separate power and ground, so we run a positive wire directly to the fuse box and a negative wire to a good ground. Two wires are connected to the positive and negative sides of the coil, and the coil’s previous wiring is disconnected. (Note: These systems actually can be used with the points as a switching mechanism, but we don’t normally do it this way.)

At this point the MSD and Second Strike differ in their wiring, with the MSD needing a few more connections, but in both cases the instructions are very clear. Finally, the tachometer needs to be dealt with. For many cars, this is just a matter of relocating the tach lead on the negative side of the coil to the MSD or Second Strike tach output.

Getting the tach to work correctly is a bit of a challenge on a lot of British cars with electric tachs built prior to 1972. These cars used an inductive pickup off the coil to sense sparks. Because the MSD and Second Strike units produce multiple sparks, these tachs will perform erratically. The solution varies from car to car, so we recommend contacting the manufacturer tech support or someone who has done the conversion to get the specific answer for your car.

If we’re installing a Second Strike, we then adjust the rev limiter with the dials on the unit. If we’re installing an MSD 6AL, we make sure we’ve got the right plug-in chip for the rev limit we want. With an MGB or MGA, we usually set the limiters to 6000 rpm.

Compared to the MGB with just the Ignitor alone, you can see (check the dyno graph) that adding a multiple spark capacitance discharge system (in this case an MSD 6A) increases engine output by about 1 horsepower.

However, the big improvement is the smoother horsepower curve, showing improved drivability.

Sample Installation: MGB With Ignitor and Lucas 45D

If we’re working on a rubber-bumper MGB, we’ll replace the stock emissions-derived electronic Lucas 41427 45D distributor with a new one. Since the new 45D still comes equipped with points, we usually replace them with an Ignitor following the steps previously outlined.

The table below shows how the work changes the engine’s output. Column 1 shows how the MGB with the stock electronic distributor performs on a chassis dyno. Column 2 shows how the points-equipped 45D’s advance curve improves low-end power, yet those points wind up hurting top-end power. Column 3 shows how the Ignitor improves both the high- and low-end power.

Sample Installation: MGB With D.U.I. Distributor

The D.U.I. ignition is a modified GM HEI unit. With its self-contained coil, it’s a simple all-in-one unit. Although it’s a tight fit in an MGB, it performs well once installed.

When we first received a D.U.I. distributor, we were pretty skeptical. Gargantuan in comparison to the Lucas 25D previously installed on our “mule” MGB GT, we wondered if the new unit would even fit in the engine bay.

Turns out it does, but not without some work.

On our car, after removing the stock distributor we had to reposition the rear oil cooler line slightly to free up enough space for the D.U.I. On other cars, it may also be necessary to reposition the oil filter housing. Neither is a difficult job, but it shows how tight the clearance is around this unit.

After making sure the distributor clears the oil cooler lines, we had to go through a bit of jockeying to get the long and wide distributor installed: The cap cannot be installed or removed with the distributor installed on the engine, while on the other hand, the distributor cannot be installed with the cap fully installed on the distributor.

We had to loosen the cap’s four clips and cock the cap to a 30-degree angle as we slipped the distributor into the engine. Once the distributor was on the engine, we could put the cap back on. Tightening the hold-down clips became a chore, however, since the bottom two were inaccessible. Rotating the distributor about 90 degrees in each direction solved this problem and we had it installed. Wiring is a simple three-wire hookup.

Despite our initial skepticism and the installation challenges, we’ve been impressed with this distributor once it was installed. The dyno chart shows it compared to an Ignitor and MSD-based Lucas 25D. The D.U.I. piece made slightly better power and drivability is smooth and excellent. We just hope we don’t need to remove it again anytime soon.

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