Distributor Installation - Don't Just Drop It In

In addition to timing the distributor to the firing cycle, the distributor must be in time with itself. Racers often work on the internal advance system. In stock form, the HEI's rotor always points close to a terminal in the cap when the ignition is properly timed. Once the advance mechanism has been modified, the relative position of the rotor and a cap terminal must be checked. Because of the strength of the generated spark, the rotor must point to the correct terminal, not somewhere between two of them. An HEI ignition can easily fire across a 1/2-inch gap.

First take a look at what makes the rotor, cap, and pickup coil stay in relation to each other. When the vacuum advance mechanism is removed, the plate holding the pickup coil is free to move around. A racer could fabricate something to keep the pickup coil from rotating. Were this done without regard to its positioning, the alignment of the reluctor and pickup coil could be considerably out of phase. This would signal the coil to fire at a time when the rotor is between terminals. The cure is not to just pull off the vacuum hose. The vacuum canister contains a spring and a rubber diaphragm. This unit can bounce around, flexing from vibration as the engine runs or the car responds to a rough track surface.

The cure is to use a vacuum lock-out plate, available from Performance Distributors. This plate bolts in and solidly restrains the reluctor's movement. It is made so that the position of the reluctor to the pickup coil is correct.

If you have modified the advance parts at the top of the rotor shaft, there are some other things to do. Here the rotor-to-terminal timing can go astray. There are several ways to change these parts. The springs on the advance weights can be changed as well as the weights themselves.

The results can be iffy if you don't have access to a distributor machine to check your work. Possibly the best way to obtain the necessary results is to get the distributor to a reputable shop. It should have the correct parts installed and in proper alignment.

There is another way to achieve these goals. The following modification is often used by circle track racers. The advance mechanism, weights and springs, are removed. The football-shaped plate is then welded to a larger plate. This totally removes any advance function in the distributor. It can also cause ignition problems. If the shaft is not removed from the distributor, there is a possibility of damaging the pickup coil. Next, since they can move against each other, the plates can be welded together in a position that would allow the rotor to fire to either of two terminals. Careful attention to the location of these plates in relation to each other can alleviate the problem. There is one more simple solution: Performance Distributors offers a plate with the holes in correct alignment that replaces the weights and springs.