Setting Breaker Points

Almost every day we will receive an e-mail or telephone call tech question on how to set the breaker points on single, but mostly dual breaker point, distributors. It surprises me as to how many people that have been "Doing This For Years" still do not really know how a dual point ignition works or how to correctly adjust the breaker point settings on their distributor. Here within this article we hope to make it clear for you.

MYTHS:

There are many myths surrounding dual point ignitions, here is a list of the most popular.

• Dual Point distributors operate opposite cylinders or opposite sides of the engine. Absolutely false! The dual point distributor only increases coil output (duration) for better performance in spark energy output from the coil, and for better high RPM operation.
• A point set is two breaker points. Not true. A point set is ONE point set, meaning a set of contacts is part of just one point set. Dual point distributors require (2) sets of points, which would be four contact points.
• Dual Point distributors are set with a matchbook cover for gap or a feeler gauge. Well, this is half right. The gap is actually a starting point. Correct point gap is only accurately set with a dwell meter. Different distributor designs, brands, and engines (4 cylinder vs. 6 cylinder vs. 8-cylinder) can and will have different required settings.
• Dual Point ignitions are better than electronic. Absolutely false. In many cases a point ignition "may" be more reliable if your electrical system on your vehicle keeps killing electronic ignition modules, but points are definitely not better than electronic. Electronic triggers offer better coil saturation, better RPM, no need for adjustments, and smoother running at all RPM levels.

HOW CONTACT POINT IGNITIONS WORK:

Contact point (also known as breaker point) ignitions have been around almost forever, and are fairly simple. As the engine spins the distributor shaft (by a gear or drive dog), there is a cam wheel mounted to the distributor shaft. Just off of the cam is the a single set (or two point sets with dual point distributors) of breaker points that are opened and closed by the distributor cam's contact with the point set(s). When the points open and close, they allow the coil to energize and then release the built up energy through the cap, rotor, into the spark plug wires to the spark plugs. How long the points stay closed is the DWELL.

The dwell is controlled by the design of the distributor (distributor point cam, point design, and adjustment). The point adjustment is simply how close each point set is to the point cam. The closer the points are to the point cam, the larger the point gap (dwell), thus the further away you will have less gap and lower dwell (less time the points are closed).

Too much dwell can cause a late spark, rough running, lack of RPM potential, early point and condenser failures. Too little dwell causes a weak spark, overheated points, "stuck" points, poor engine performance, and more. As you can see, correctly setting the optimum point gap is mandatory if you want reliability and good performance. But, as the points wear, the dwell time will increase, therefore requiring periodic adjustments of the dwell settings so as to maintain maximum reliability and performance of the system..

We once had a customer argue with me that "Brand X" distributor must be a P.O.S, because his OEM distributor had a longer dwell setting. This individual could not understand that the dwell is a number based not only upon what the system needs, but by the inherent engineering of the distributor. If one distributor has a cam wheel that is "X" diameter, and another has "Z" diameter, there is NO possible way they can have the same dwell, even if used in the same engine. This can also occur from point design (arc angle, length, fulcrum position, etc), or other engineering variances. In other words, DO NOT base distributor performance on a dwell specification. If you were really so worried about maximum performance you would not be using a breaker point system, you would be using an electronic system.

I will give you the settings for the Mallory distributors below. As you will notice, the settings for 4, 6, or 8 cylinder applications vary. DO NOT simply rely on the point gap settings, you MUST use a dwell meter for accuracy.

8-Cylinder engine applications (Mallory Distributors)

6-Cylinder engine applications (Mallory Distributors)

4-Cylinder engine applications (Mallory Distributors)

FREQUENTLY ASKED QUESTIONS:

Ok, I have the gaps and dwell settings, but how do I set them?

This will probably screw up everything about points that you have ever been taught, especially dual point settings, but at least now you will be able to set them correctly.

For single point distributors it is very simple. Just pre-set the point "gap" by using a feeler gauge of the correct thickness and placing it between the contacts on the point set. You must have the rub point of the point set touching the highest part of one of the cam lobes when you do this The easiest way is to spin the rotor by hand slightly (you should be able to do this since there is play from the mechanical advance curve in the distributor) so that the rub pad on the point set opens the point set. Snug the screws holding the point set and you are ready to spin the engine.

Now, with the (Safety Note) ignition coil wire removed, the cap and rotor off the distributor, and a dwell meter properly connected to the coil, you can spin the engine. The best way to do this is with a remote starter button. The only other way to do this is with someone assisting you. Crank the engine and watch the reading shown on the dwell meter.

If the dwell reading is not within the specifications, you must adjust the point set (the procedure above is the easiest) and securely tighten the point set mounting screws. The (±) in your specification settings means "plus or minus", so if the dwell is supposed to be 32° ± 2°, this means that 32° is the optimum setting, but between 30° - 34° is acceptable.

For Dual Point distributors there is a bit more effort involved. You can still set the point gap on the "primary" point set in the distributor (see note below), but you might as well forget the secondary point set at this moment.

To set dual point ignitions you first block the "secondary" point set. You can block it by either not having it in the distributor, or using a thin piece of cardboard such as a matchbook cover between the contacts of the secondary point set. With the same (Safety Precautions) as above: ignition coil wire removed, the cap and rotor off the distributor, and a dwell meter properly connected to the coil, you can spin the engine. The best way to do this is with a remote starter button. The only other way to do this is with someone assisting you. Crank the engine and watch the reading on the dwell meter. You will be setting ONLY the primary point to the required setting at this time.

After you have set the primary point set to the required dwell, install or unblock the secondary point set. You will now spin the engine again and by adjusting ONLY the secondary point set, adjust the the secondary point so that the dwell reading matches the "combined" dwell specification. You do not have to touch the primary set again.

TROUBLESHOOTING:

There is really not much that can go wrong with a breaker point ignition system. But, I've listed below some common problems, what the possible causes are, and hopefully how to fix it.

CONCLUSION:

As I've always stated throughout this article and in thousands of conversations with our customers, the best fix for a point distributor is to upgrade to an electronic trigger style. Breaker points are Model A technology, why would you want that on your vehicle? Electronic triggers offer you substantial improvements:

back to the Tech Zone

Mallory Ignition Main Page

Accel Ignition Main Page