"We put each one on the distributor machine and get a good racing advance dialed into it specifically for the engine it's going on. Ninety percent of the distributors we sell have the mechanical advance set in it with the weights and springs. Of course, they are our own weights and springs, not the stock stuff. With stock weights and springs, we've found there's a chance for over-advance. When the stock pieces are allowed to wear, they can start to advance the engine as much as 4 extra degrees and then the engine gets into detonation. You have to make sure the advance is nice and stable."

In order to dial in the advance specifically to your engine, the ignition builder will need some specific information. Before dialing in the advance curve, Davis says he needs to know the camshaft duration, compression ratio, type of fuel, weight of race car, whether the carburetor is a two- barrel or four-barrel, and the rpm range you most likely will be running so that he can match the advance to the engine's powerband.

Installation and Maintenance With only one wire to hook up, an HEI is the easiest ignition out there to install in a race car, but it still requires care to make sure it sits in the engine and engages the camshaft's distributor gear correctly. "Whenever you install a distributor, you want to check and make sure it isn't bottoming out," Davis explains. "After you put the distributor in the motor, pull the cap and lift up on the distributor shaft assembly to make sure it isn't bottoming in the block. If you can lift up on the distributor shaft and get a few thousandths of an inch of play, then you are OK. If the shaft won't budge, then you need to use shims to lift the distributor up a few thousandths. That will prevent the distributor shaft from getting in a bind and tearing up."

Once the ignition is installed correctly, maintenance really only consists of regularly checking the assembly for damage or wear. Davis recommends inspecting the cap and rotor periodically. If the spark is jumping around inside the cap, you will notice brown burn marks on top of the rotor. With some units that use metal screws inside the cap, the screws themselves can actually act as a ground and cause this. To avoid this, Performance Distributors uses nylon hold-down screws that are electrically inert. Burn marks on the rotor is also a sign that the plug wires are offering too much resistance. You either have a damaged wire, or the wires you are using need to be upgraded.

HEI Distributor Myths
Davis tells us that despite the remarkable advancements Performance Distributors and other companies have made to improve the old HEI system, there are still several misconceptions about the ignition out there. Here's a few he gave us:

Myth #1: Inductive Ignitions, such as HEI, are not as good for racing as capacitive discharge ignitions. It Depends On The Application. Today, high-output HEI modules and coils that saturate fast enough to fire consistently at high rpm are being made. This also allows wider spark plug gaps. A benefit of wider plug gaps may be a more complete burn of the air and fuel mixture.

Myth #2: Internal Coils (In The Cap) Overheat. HEI coils can run cooler because they are encapsulated in epoxy, which dissipates heat more efficiently than oil-filled coils. The solid epoxy, in comparison to oil-filled coils, also eliminates the possibility of leaks.

Myth #3: Ignition coils last forever. For peak operation, change the coil after each season. They can lose efficiency, so a new one should be installed. You should also do the same with the spark plug wires.

Myth #4: Lock the advance and race. A fully-locked advance usually leads to hard starts. Your motor may run better with less-than-total advance at some rpm. The upside of a locked advance is that you don't have weights and springs that can wear and potentially fail.

Myth #5: You have to run an alternator with an HEI system. Any electronic ignition system, whether it is capacitive discharge or inductive (HEI), will run optimally with an alternator. The more input voltage you put into an ignition, the more output you get out of it. Some HEI systems only draw two to three amps off the battery. Capacitive discharge draw between six and 14 amps off the battery. An alternator will keep both the battery and the ignition at their optimum for the entire race. Remember, an alternator draws less than 1 hp. (Another myth is that alternators rob too much horsepower.)

Myth #6: Because this is a race car, use solid-core plug wires. HEI systems run better with spiral-core wires. The spiral core prevents internal wire vibration and electronic interference.

Myth #7: The dielectric grease you place under an HEI module insulates the heat. No. In fact, the grease transfers the heat produced by the module to the distributor housing. The HEI housing actually becomes a heat sink.

Myth #8: You must phase the rotor on an HEI. On an HEI, if you install your vacuum advance eliminator using the holes in the housing that were originally for the vacuum advance, there is no cause for rotor phasing. It will already be phased correctly due to the original design.

SOURCE
Performance Distributors
Memphis
TN
9-01/-396-5783
performancedistributors.com