Electronic Ignition for Your Old Sports Car

story and photos by tim suddard

Ignition points were used on just about every car manufactured up untilthe mid-'70s. Their purpose is to trigger the ignition or tell the coilwhen it is time to generate a spark. When set perfectly (a difficult task),points work pretty well-at least at low rpm.

Unfortunately, there are some down sides to points. First, unless thedistributor shaft is completely round and has no wear (which is highly unlikely)the points are compromised in their ability to do their job. At high rpm,points begin to float or vary in their accuracy. They are also subject towear, and need to replaced about every 10,000 miles. This job, combinedwith the rest of the traditional tuneup, takes an hour or two and can costupwards of $50, depending on what you drive and which parts are worn out.

The upside of points as an ignition triggering device is that they arecheap, initially, and if replaced every 10,000 miles they seldom fail. People(especially old-time racers) trust points.

This trust, combined with a reluctance to adapt to the changing waysof the world and a fear of anything not understood, has led many of us toresist electronic ignition of any kind. Forty years ago, no car had electronicignition. Today, you won't find a car manufactured without it.

The 1970s were the turning point in the installation of electronic ignition.When manufacturers had to meet new fuel economy, reliability and emissionsstandards, most turned to electronic ignition as a partial means to meetthose standards. The electronic ignition systems now offered on all newcars offer improved fuel mileage, better acceleration, less overall costand a cleaner running car.

But what about your poor old sports car? How do you add electronic ignitionto it? Many companies, including MSD and Jacobs, make aftermarket ignitionmodules that you can add to your older car. While very good, these productsstill use the points as a triggering device for the ignition. Granted, theseproducts will work with most triggering devices, but they are sold assumingthat you will be retaining your points. Electromotive and MSD also offera true crank-fire ignition, which is great for racing but a little morecomplicated than some people will want for their daily driver.

Crane and Lumenition offer an optical switch to replace your points aspart of their electronic ignition system. Crane was formerly known as Allison;Lumenition is distributed in this country through XKs Unlimited. Their systemuses an optical switch containing a light emitting diode (LED) that sitsopposite a matching silicon phototransistor. When the ignition is switchedon, the LED emits an invisible infrared beam toward the phototransistor,which receives, or "sees," the beam. An interrupter, or "chopper,"fitted to the distributor shaft rotates in the path of the infrared beam,causing a pulse. The chopper has one blade for each cylinder of the engine.A power module receives the pulse and switches the ignition coil on andoff. The coil produces a high-tension spark when switched off and is rechargedwhen switched on.

We recently installed the Lumenition system on a 1964 Morris Mini Minor's850cc engine. Each system is custom-made for the application, and virtuallyall British sports cars are listed. We used model PMA 50, which retailsfor $149.95, and fitting kit FK116, which is $39.95. This is their basereplacement system. For another $80 you can get the CEK 150, which offersa hotter spark for high-rpm and racing situations. The fitting kits varyin price from $15 up to about $40 with a couple of exceptions. We decidedthat the 850cc Mini, with 25 horsepower at the front wheels, did not needthe more expensive system. Neither do you unless you are racing or regularlysee over 6000 rpm on your tachometer.

The beauty of this system is that once it's properly installed, it neverneeds adjustment and there are no parts touching each other that could wearout. Another neat thing about the Lumenition system is that it is the mostcompact electronic ignition system that we have ever seen. The module isthe size of a cigarette pack and weighs only a few ounces. The optical triggerweighs less than the points it replaces. XKs Unlimited claims the additionalbenefits of more accurate timing and longer dwell, which makes sense giventhe design of the system.

Installation of this system is very straightforward. The directions arewell written and only simple hand tools and an electric drill are needed.A voltmeter and a timing light would also be handy.

1. First, disconnect the negative terminal of the battery. Then mountthe Lumenition box with the two screws provided. A cool, dry location ispreferred, which may be a trick to find in most British cars. We mountedours high on the Mini's right-side inner fender wall. Obviously, you'llwant to mount it close enough to the distributor and coil so that the wiresreach. Mount the attached ground wire right underneath the module.
2. Connect the red wire to ignition-switch side of the ballast resistor.
3. Next, attach the brown wire to the wire that originally went to thepoints. This wire goes to the negative terminal of the coil (sometimes throughthe tachometer).
4. Install the optical switch in place of the points. You may need toshim this switch so that the "chopper" does not hit either thepin that the points sit on or the electric eye.
5. Make sure you put the rotor button back on and adjust the static timingas per the instructions.
6. Connect the plug from the optical trigger to the ignition module, reconnect the battery and you are done.

We'd recommend the Lumenition ignition to all our readers with old Britishcars. If you are nervous about the electronics failing, keep an extra eyeand/or control module in your trunk as you would carry any extra parts.That way even an old-fashioned kind of guy can enjoy modern technology.

source

XKs UNLIMITED
850 Fiero Lane
San Luis Obispo, CA 93401
(800) 544-7864
E-mail: XKS UNLTD@aol.com

The entire Lumenition system is quite simple and takes about anhour to install. Just follow the well-written instructions.

The wiring is very straightforward on this system. We had no troubleunderstanding the directions.

The Lumenition optical trigger fires the coil with an infraredbeam of light that is broken by a plastic "chopper" wheel mountedto the distributor shaft.