 Mallory offers a variety of distributor triggering and dimensional designs to meet the needs of almost everyone. This section will describe the variations, good and bad points, and help you to make an educated choice for your application.
When you are trying to make a decision as what type of distributor you need for your vehicle or boat, the choices can be too many and confusing as to their construction, purpose, and benefit. We are here to clean up the mess a bit so that you can know what is the best choice. Something to add to the confusion is that in many cases the choice is a matter of personal preference. You have to weight the differences in technology, cost, and benefits to your wallet and application.
The three primary definitions are breaker point, electronic, or magnetic. There are variations of these styles (Hall Effect, for example), but they still fall into the base choices above. Some styles utilize internal coil drivers, while others are required to have a separate ignition control amplifier, computer, or other component.
MYTH - Installing a high output coil will increase spark output. Yes, and No. Consider your coil like a pair of shoes. You would not wear rubber sandals to climb Mt Everest, nor would you wear snow boots to cross the Mojave desert in the heat of summer. The ignition coil only does what it is told by the distributor or by an external amplifier. Just match the coil to the demands of the ignition, engine, and intended use (operating distance and RPM range) of the vehicle. If you happen to have a coil that can't keep up, of course adding a better coil will show improvements.
With most of the Mallory distributors you can easily make changes to the timing curve and total timing allowed by using one of the Mallory Advance Curve Change Kits (sold separately).
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Otherwise known as contact points, dual point (two sets of points working together to increase coil saturation for higher RPM potential), or just plain point distributors, these are the most simple of design. A breaker point distributor is fairly reliable, and just about anyone can keep them running with some basic knowledge of how they work. Understand though that breaker point systems are quite antiquated for the modern world. Even if everything in your engine is perfect (internal components, ignition, and fuel system) you will never see more than 20k volts distributed from your coil, no matter the rated output of your coil you have installed.
Breaker point systems are inexpensive, yet require constant adjustment and parts replacement (points and condenser). You need to pay attention to condenser housing grounding, point wear, and correct dwell settings. Please use a dwell meter to set them ... sliding a feeler gauge or paper matchbook cover into them would be like have a blind dentist drill your teeth. When you see a gap setting it is just a guide for use in an emergency just to get you moving. If you want the points to last and perform properly you must adjust them to the correct specifications with the proper equipment. Use this guide, How to Set Breaker Points to assist you. As the points wear they should periodically be checked both visually and with the dwell meter to make sure they can reliably do their job.
In the past, more than once I have ended up in an argument with a customer in regards to dwell settings. One customer stated that the Mallory distributor could not be very good because the dwell specification on the Mallory was less than his OEM Nissan distributor. I did my best not to laugh because he obviously did not understand what calculates the dwell angle, but he was insistent that I was wrong. The dwell angle is going to vary from brand to brand unless the point cam dimensions, point arm placement and arm length are all the same on each and every brand distributor. The dwell setting is not a measurement of performance, only an engineering calculation that combines the specs of that distributor with the engine requirements.
You can use a breaker point distributor on vehicles with 6-volt and 12-volt electrical systems. On a 12-volt system you must use a ballast resistor to drop the voltage, otherwise rapid point failure will occur. Vehicles with breaker point distributors also had what was called a Boost Wire or Start-Assist Wire in the wire loom from the starter to the coil. This added wire bypassed the ballast resistor during cranking to assist with cold start-ups. This is the only time you would want to bypass the ballast, though decades ago there were components to bypass the ballast when drag racing to get a bit more energy in the system. These were only activated when staging the car for the race, and turned off at the end of the pass.
If you must use a breaker point distributor, always consider the possibility of a future upgrade to electronic ignition. You won't be able to upgrade a vacuum advance distributor (discussed later). The Mallory Unilite® Electronic Conversion Kits include the same components that you would have if you had purchased a complete electronic distributor, and take only about 15-30 minutes for a rookie to install. With the distributor on the bench I can swap one out in about 5 minutes. Plus, in many cases you will save money purchasing the separate components.
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The Mallory Unilite® is honestly the flagship product of the company. Still, after all of these years the Unilite® is considered the most accurate ignition trigger produced by any manufacturer. A similar design is now used in recent GM applications, called the opti-spark. The Unilite® trigger is a photo-optic L.E.D. module that resides within the bowl area of the distributor. The L.E.D. beams a constant light across the two towers of the module and a windowed rotor blocks and then unblocks the optic. When the optic is blocked it is energizing the coil and when the window momentarily unblocks the optic it tells the coil to release the built up energy to the distributor cap and out to the spark plugs. Being able to trigger the coil means that the Unilite® has a coil driver built into it, thus a separate ignition unit/amplifier is not a requirement but a nice addition in many applications.
NEWS FLASH: Mallory now offers a better and lower-priced replacement module called the E-Spark. This module functions identically to the Unilite®, has the same basic dimensions, wiring, etc. Save some $$$ when replacing a module by ordering the E-Spark Module part #MAL-6100M.
When you select a Unilite® distributor you are usually making the best choice. Accuracy, nothing to adjust, compatibility with the Mallory Hyfire® ignition amplifiers and also other brand ignition controls. With a basic distributor & coil setup (no amplifier) you will get over 32K volts of coil out put. Set your ignition timing and forget about it. You will need to use ONE of these components along with your Mallory Unilite® Distributor. Either a ballast resistor (Mallory part #MAL-700 is best), and OEM resistance wire, internally resisted coil, or external ignition amplifier. The reason for this is that the Unilite® must have a drop in voltage to function. Not having a drop in voltage will kill the module.
Many people ask about the wiring connections for this distributor. There is just three simple connections to make. Basically a ground connection to the engine block, and then one to each side of the coil. That is the simple explanation but you need to follow the installation instructions due to slight variations in each specific application. Another important feature is that every Mallory Unilite® is warranted for a full 12-months from the purchase date.
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 (Magnetic Breakerless Ignition) DISTRIBUTORS
The M.B.I. is similar to the Mallory Unilite®, but instead of a photo-optic trigger the M.B.I. uses a magnetic pickup and electronic module to trigger the coil. The electronics of the M.B.I. module are almost identical to that of the Unilite®, but it is the trigger itself that is different. You have a star-shaped reluctor mounted to the shaft and the pickup is part of the module.
The M.B.I. was created to fill the need of those who preferred the magnetic trigger, while still offering the electronics so as to drive a coil without an external ignition unit/amplifier. It is our opinion that the M.B.I. is more of a preference issue. It is slightly less expensive than the Unilite®, yet it is not as accurate. Durability is virtually the same as the Unilite® or any other brand electronic trigger style.
One issue that most people never bring up is that any magnetic style trigger, no matter the brand, is going to cause a slight retard in your ignition timing. Think of how magnets actually work. They never just snap apart ... they keep pulling a bit until you exceed the distance that magnet's grab can reach. Sort of like when blowing soap bubbles off a small ring. The bubble stretches and stretches until it snaps off, then wobbles around a bit until it becomes concentric. With a magnetic trigger you get the same. As the reluctor flies past the pickup the pickup starts to grab early, then releases late. This can cause a variation (retard) of timing to as much as 1° per thousand RPM (or more). In a critical racing engine this is not acceptable, and engine builders will have to use expensive ignition amplifiers or computer controllers that have the ability to compensate for the delay in the trigger style.
The M.B.I. is accurate as it can be, but its not a Unilite®. You have nothing to adjust, compatibility with the Mallory Hyfire® ignition amplifiers and also other brand ignition controls. Set your ignition timing and forget about it, with only a simple check to verify the air gap between the pickup and reluctor. You will need to use ONE of these components along with your Mallory M.B.I. Distributor for it function properly: Either a ballast resistor (Mallory part #MAL-700 is best), and OEM resistance wire, internally resisted coil, or external ignition amplifier. The reason for this is that the Unilite® must have a drop in voltage to function. Not having a drop in voltage will kill the module.
Many people ask about the wiring connections for this distributor. There is just three simple connections to make. Basically a ground connection to the engine block, and then one to each side of the coil. That is the simple explanation but you need to follow the installation instructions due to slight variations in each specific application. Another important feature is that every Mallory M.B.I. module is warranted for a full 12-months from the purchase date.
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The first thing you need to know about a 2-Wire Magnetic trigger style is that you must use an external ignition amplifier/control unit with it. The 2-wire is simple, reliable, and pretty much idiot-proof. The benefit of it is that you really do not have anything that can fail, there are no electronics. The downside is also tied to its benefit in that you must use an external amplifier, and if that amplifier were to fail, your stuck. Unless you have a replacement amplifier, your stranded. In the case of the Unilite® or M.B.I. you can also bypass the amplifier (if using one) if the box were to fail and get yourself home with just the distributor and coil.
Most every race-only, high horsepower gasoline engine uses a 2-wire magnetic trigger style. This includes both distributor or crank trigger systems, and both operate with a 2-wire pickup. One would be a stationary pickup and reluctor (distributor), or the flying magnet style of the crank trigger. These systems simplify your ignition, while taking away a few features and requiring other more expensive components.
One issue that most people never bring up is that any magnetic style trigger, no matter the brand, is going to cause a slight retard in your ignition timing. Think of how magnets actually work. They never just snap apart ... they keep pulling a bit until you exceed the distance that magnet's grab can reach. Sort of like when blowing soap bubbles off a small ring. The bubble stretches and stretches until it snaps off, then wobbles around a bit until it becomes concentric. With a magnetic trigger you get the same. As the reluctor flies past the pickup the pickup starts to grab early, then releases late. This can cause a variation (retard) of timing to as much as 1° per thousand RPM (or more). In a critical racing engine this is not acceptable, and engine builders will have to use expensive ignition amplifiers or computer controllers that have the ability to compensate for the delay in the trigger style.
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 DISTRIBUTORS
Mallory also offers a variation of the GM HEI for a simple and reliable upgrade over breaker point or worn-out non-computer controlled factory HEI applications. These are a very inexpensive upgrade, that offer some nice benefits. You will have nothing to adjust, unless you want to mess with the timing curve, and the factory settings are optimum for over 90% of the applications they are purchased for.
The dimensions of the HEI are the only issues you need to concern yourself with. You have a fairly large cap with these distributors, and having a coil within the cap does not help contain the dimensions. Some vehicles may have issues with firewall clearance and they won't work with most roots style supercharger systems. These distributors work excellent in many circle track applications that require OEM or HEI style distributors.
You can use the Mallory HEI in performance and racing applications, plus they will work with all aftermarket ignition amplifiers such as the Mallory Hyfire®. We do suggest though that if you do decide to use an amplifier that you consider two suggestions. The first is to not use the internal module, just remove it. Your ignition unit will connect directly to the pickup in the distributor. The second suggestion is to go to either a more race-oriented coil, or better yet to go to a remote coil kit and use one of the Mallory Promaster series coils.
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 TRIGGER DISTRIBUTORS
Mallory also offers a few distributors that have special triggers in them to meet the needs of Edelbrock and other fuel injection systems. The image at left is that of a Mallory distributor (part #MAL-6148201) for Chevrolet V8 engines using the Edelbrock Fuel injection.
Many injection and computer systems require a signal that is different from what the Unilite® or M.B.I. can provide. In the case of the distributor shown at right, the trigger is a Mallory designed Hall Effect. The Hall Effect provides what is called a square wave signal.
 Other distributors include a crank trigger distributor ... no crank trigger, or any trigger inside for that matter, but it is designed to work in conjunction with your crank trigger system as a place to connect your plug wires. Mallory also makes a special 75-Series Distributor with the new Hyfire® HEI Module (part#MAL-699) shown at left. This module is specially designed with extended dwell circuitry to provide a hotter spark over an extended RPM range, plus it has a built-in adjustable rev limiter that allows easy adjustment between 4,000 and 8,500 RPM.
Mallory also offers replacement distributors for the Ford TFI (78 & 79-series), and for the GM HEI/EST (80-series) engine applications.
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 vs. MECHANICAL ADVANCE DISTRIBUTORS
The very first comment we must make about this topic is that with either style Mallory distributor that the mechanical advance curve is identical in both. That means that if you were to order a Unilite® distributor for an early small block Chevy engine, part#3748201 (mechanical advance), or a #4748201 (vacuum advance), both will have a an identical total timing of 24° that is all in by roughly 3,200 RPM.
All the Mallory vacuum advance distributors have adjustable diaphragms so you can adjust the amount of added timing offered. All you need is a 3/32" Allen wrench, inserted through the port connection to adjust the preload on the diaphragm.
There are two ways to setup (connect) your vacuum advance line to your engine. You can connect to either a "ported" vacuum source, or a "manifold" vacuum source. Now I'll explain the differences, but I will start with a bit of history. When vacuum advance was first utilized it was connected to ported vacuum. Ported vacuum is a connection point that is above the throttle blade of your carburetor. With a ported vacuum connection vacuum increases to the port as RPM increases. With a manifold vacuum connection you are connecting to a point that is below the throttle blades. When unleaded showed up in the 1970's, the engineers were trying to do whatever it took to reduce emissions (meet federal and various state standards) and at the same time conserve fuel. The problem was the limited learning curve that they had working with the hotter and faster-burning fuels and early emission components.
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Old-School Total Timing
(connected to ported vacuum source):
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Initial + Mechanical + Vacuum = Total |
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Early "smog years" w/Vacuum Advance
(connected to manifold vacuum source):
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Initial + Mechanical = Total |
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Modern Mechanical Advance "only" Distributor:
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Initial + Mechanical = Total (+ Vacuum) |
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(Total Timing being all that your engine wants) |
Soon after unleaded fuels were released, engines started coming from the factory with the vacuum advance connected to manifold vacuum. With manifold vacuum you have the most vacuum at idle or in low-load situations. As engine load increases the vacuum is reduced. The engineers, instead of changing technology to keep up with the new fuels, emission requirements, and fuel shortages, they merely tossed on a few band-aids. One of which was trying to increase combustion temperatures to not only falsely believe it would help burn off more emissions, but to help catalytic converters get hot enough to do their job. The thinking was to give as much timing as possible at lower load and then as load increases the timing is removed. These engines were running so hot and were gutless as hell. No power, too much heat, no pulling power, limited life span, and horrible fuel efficiency. In many cases the engines ran better and had lower emissions before all the emission components came into use. New vehicle owners were quick to gut the emission components, not realizing the problems were deeper than just a few bolt-on emission devices.
The engineers had part of the theory correct in that if you could add more initial timing, and then pull it out under load it would help the engine's efficiency. The problem was within the management of the timing. They setup these systems with way too much timing, exceeding what the engine could effectively use, causing reduced engine life, too much coolant heat, and lost power. A Chevy V8 that would only need 34-40° total timing was now seeing upwards of 60°. The igniting point was so far before the piston coming to TDC that the pistons were fighting against themselves just to get to the top of the cylinder.
So, what do you choose? Many of the installation instructions for distributors and carburetors alike still show you connecting to ported vacuum. The problem with ported is that there is that too much timing coming on when you don't want it, usually when your trying to climb a grade or pass. If you're not careful you will have substantial detonation and engine damage. Change to manifold vacuum and if you don't adjust the vacuum down to where it is giving you no more than about 8-10° extra you will have way too much heat, and an increase in emissions that could cause you to fail a smog test. Not to mention lost power and inefficient combustion.
Others will argue for benefits of added fuel economy from a vacuum advance distributor. Ok, sure it is possible if you want to spend countless hours fine tuning the timing curve to find out what your engine is going to be comfortable with. It does not take being off very far to give you the opposite effect and hurt fuel economy and efficiency. There are far better options to improve fuel efficiency instead of relying on vacuum advance to do so. Free flowing exhaust, converting to fuel injection or at least a more efficient carburetor, etc.
In reality, the only time you need vacuum advance is to meet state laws. If you decide to use it you will need to carefully plot your timing curve so that you meet the demands of your engine. Most of our customers that experiment with it will usually end up just blocking it off if their state laws allow it. Trial and error with your engine and driving habits will be the only way to set a vacuum advance system to meet your needs. We've come a long way though. Modern fuel-injected engines no longer need vacuum advance because the computer is able to better manage the timing the engine needs based upon the various sensors it receives data from.
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 DISTRIBUTOR
We are not going to get into too many details to each cap style Mallory offers, just the most common. When you order a Mallory distributor, one of your concerns is going to be the cap. If you have unlimited room in your engine you can just select the distributor style you want and away you go. But, if you have specific needs like firewall clearance, marine use, supercharger, or other space limiting components, you will need to be aware of what is available. Below I will describe the most common styles and any positives or negatives. There are only a few cap styles that can swap around. The cap style used is inherent to the distributor housing it come on. For example, none of the flat caps will fit on a stack cap style distributor, and vice-versa.
- Marine vs. Automotive: Mallory offers different caps for either Marine or Automotive applications. Not having a marine style cap on your boat can cause grave consequences. Automotive caps are vented, where as the marine versions are non-vented. You do not want a vented cap on marine applications because the fuel vapors can enter the cap and ignite, turning your boat into a Roman candle. The only problem with using a marine cap on your automotive distributor is by not having the vent you increase the ionized air in the cap which can cause misfiring and module failures if it becomes excessive.
- Standard Stack Cap: This is the most common cap style that is available on most of the popular distributor part numbers. This is a socket style cap, or female, meaning that the plug wire goes inside of the cap socket connection. The carbon contact in the center of the cap is spring-loaded. This cap is available in both automotive and marine versions.
- High Energy Style Stack Cap: This is a variation of the socket style cap but uses the spark-plug tip style male connections and in some cases also includes the plug wire girdle (as shown in the image at right). Some people prefer this style due to the more secure connection it provides.
- Mini-Bowl Cap: This cap is used only on those distributors that have a very small bowl diameter for tight clearance applications. These came on some early Mallory 4 and 6-cylinder distributors. You would find this on some Volkswagen, Nissan, and other applications where the distributor is stuck between a pair of Weber style carburetors.
- Flat Cap (crab cap): This is like the bastard step child of all the caps. It does give you the most clearance when you need it, but never select this style just because you like the look. The manufacturing process for this style cap is difficult and with it comes a great many problems. Cross firing and fissure cracks are the most common because the brass contact connections tend to move a bit during the injection molding process. You will notice these caps are heavy and thick to prevent these occurrences, but it is no guarantee. Plus, they are expensive. Boats requiring install clearance, supercharged, and other critical clearance applications need to use this cap.
- Comp 9000 (large style) Cap: This is the standard cap on all Mallory Comp 9000 distributors, plus it is used on many magneto applications. This is similar to late model Ford style caps. It's large diameter (5") can cause clearance issues, but on high output ignitions it helps limit the possibility of cross firing and makes it easy to install the plug wires.
- 205 Cap: The #205 cap style is used on some special Mallory distributors and magnetos. It is a fairly thick cap and uses the spark plug style terminal connections, but does not have use a girdle. This cap is slightly larger diameter than the standard stack cap styles.
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