With your Mallory distributor there may be times when you need to change out the drive gear at the base of the distributor. This may arise from normal wear, damage to the original gear, requiring a reverse gear for certain engines (mostly marine applications), or switching to a different material to mate with racing camshafts. Whatever the reason, we have created a list of available gears, what they fit, and their material at the bottom of this page. You can also read the technical info we have provided below to assist in your selection.

 

 

   The standard drive gear material which is perfect for 99% of all applications is Alloy Steel. This material is standard on all but a few race-only distributor applications. On specific applications you may need to install an Aluminum/Bronze drive gear. There is a considerable amount of confusion on when to use the aluminum/bronze gear. The gear material used is based upon the material of the camshaft that it has to mate to. You really DO NOT want to run an aluminum/bronze gear if you don't have to. These gears wear out much faster and must be periodically inspected. This means that as the gear wears, material is getting into the engine and the oiling system. If the gear starts to wear too much, engine damage may occur. On the other side though, if you run an alloy steel gear on an application using a billet steel mechanical roller cam that requires the aluminum/bronze gear, you will cause substantial engine damage.

 

   The alloy steel gears are used on all proferal billet hydraulic and mechanical flat tappet camshafts and austempered ductile iron billet hydraulic roller tappet camshafts. On hydraulic roller camshafts the core manufacturers integrate a gear into the camshaft that allows the engine builder to be able to use an alloy steel gear. This eliminates the worry and maintenance associated with aluminum.bronze gears. If you are not 100% certain of which distributor gear material to use with your camshaft, call the cam manufacturer.

 

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   With most engine applications you do not need to concern yourself with the distributor drive gear rotations, but if you have a boat, especially one with twin engines, you will want to take note.

 

   The difference between a standard and reverse gear is the tooth angle. The tooth angle is based upon the particular engine the distributor is in. There are specific circumstances where a reverse gear is required, and it is up to you to decide what is required. Just because you have an engine that spins reverse does not guarantee that you need a reverse drive gear in that engine.

 

   In twin engine marine applications there are many designs in use that may or may not use one distributor with a reverse gear. The somewhat technical jargon is that it depends on the combination of components from the list below:

   Depending on how the engine builder/boat manufacturer engineered your boat, the combination of components from the list above could go a variety of ways. Example: A standard rotation engine with a 2-gear drive and reverse ground cam = standard gear, but the same configuration with a standard ground cam equals a reverse gear. The easiest way to know what you need is to lift out your original distributors and look at the tooth angles. If both gears are the same it is safe to safe that you have standard rotation gears. If your distributors have different gears, you have one standard and one reverse gear.

 

   * The rotations listed for Mallory distributors is "rotor rotation" with LH meaning counter-clockwise and RH meaning clockwise rotor rotation. The advance system in the distributor is designed for the rotation of the distributor. You DO NOT need a reverse advance system in your distributor when you have a reverse engine. The only difference is the drive gear, and the distributor and advance rotation is not affected. With that said there are a few exceptions to that rule. One is with boats that have twin Ford 427 FE engines. For some reason the boat manufacturers built "some" of these applications to where they require reverse advance systems, in that the whole system spins reverse. Again, you need to look at what you already have to verify your needs.

 

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