There are a few things in engine building that are obvious when it comes to making power. Lightweight pistons and rods make power. Efficient combustion chambers and well-designed CNC ports make power. It's even obvious that racing oil pans with windage trays and kickouts make power. But does the ignition you use make power? After all, as long as the spark plug fires, that's all you can do, isn't it?
There is only one way to find out for sure.
Many Street Stock racing classes limit the ignition to stock-style replacement parts. For most Chevrolet and Ford engines, this means an HEI distributor is the only option. An HEI distributor is a great piece of equipment for an over-the-road car because it is completely self-contained. It requires minimal wiring and is easy to install. But without an external coil, a stock HEI cannot provide a strong spark at rpm levels commonly seen on the racetrack. Engines with higher compression or more horsepower also require a hotter spark.
One of the secrets to Performance...
One of the secrets to Performance Distributors' HEI ignitions is the high-power, low-resistance modules used to maintain a strong spark long after a stock ignition can no longer keep up.
Thankfully, modern technology provides an answer. Companies like Performance Distributors produce a race-quality HEI. The greatest differences can be found in an efficient module and the self-contained coil, which is capable of putting out much more power with less dwell time. Performance Distributors also custom tailors the advance mechanism around the needs of the engine. The result, we have been told, is a race-legal distributor that can provide a strong spark up to 9,000 rpm. By comparison, a stock HEI will have a race engine skipping and starving for power at 6,000 rpm.
To see if the distributor actually makes a difference, we traveled to KT Engine Development in Concord, North Carolina. Shop owner Ken Troutman was putting the finishing touches on a perfect dyno mule for our test. This Limited Late Model races at a track where the rule book specifies no external box or coil. By default, this means some type of HEI must be used.
The stock HEI we planned to...
The stock HEI we planned to test was one that KT Engines' owner, Ken Troutman, just happened to have on hand. After a quick inspection, it was very obvious that this unit needed a little refurbishment in order to make the test fair.
The engine for our test is the perfect candidate because it should be capable of big power and able to stress any ignition. The Chevy 350 has a 4.040-inch bore and 3.480 stroke. It is equipped with a flat-tappet cam with solid lifters. Total valve lift is 0.485 inch, and engine compression is 10.8:1. It has stock-style 23-degree heads, with 62cc combustion chambers and flat-top pistons. The Holley 500-cfm two-barrel carburetor is track mandated. The engine made peak power with both ignitions at 31 degrees advanced, so that became our fixed setting for the duration of the test. Finally, it has been outfitted with Autolite AR13 spark plugs gapped at 0.035 inch.
After properly breaking in the motor, we decided to begin the test with a stock HEI. Troutman had a stock unit that had been pulled from another engine that we initially planned to use. But a quick inspection of this unit showed that it was a bit worse for wear. To ensure that the test was fair, we had to make this distributor as good as new, or better. So, before it ever saw action, the stock distributor was treated to a new rotor, cap, and module. Only then did we consider it ready for service. Also, to make sure we weren't mistaking a problem with the stock ignition for something that was really the fault of poor plug wires, we ran the same set of Performance Distributors LiveWires for both tests.
After installing a new cap,...
After installing a new cap, rotor, and module-in addition to a good bit of cleaning-the stock HEI's performance was back to like-new condition.
On the dyno, the stock ignition functioned about the way we expected. It performed well up to approximately 5,500 rpm. After that, the ignition could no longer keep up with the engine's needs. The dyno results showed sudden dips in horsepower because the engine was misfiring. It was also quite obvious when the engine began skipping and misfiring.
Next came Performance Distributors' race-built ignition. The ignition has the same physical dimensions as a stock unit; if you order the black cap, it can easily pass as stock if your rule book requires that. We made no changes to the engine other than installing the new ignition. Oil and water temps were held within a set 10-degree range during all tests for consistency.
Like all DUI ignitions, ours arrived with advance curves customized for our engine. It also had the vacuum advance blocked off to simplify operation for racing. But the real difference is the performance coil, which features updated materials and windings versus the stock coil. The result should be less resistance to the electrical charge being generated. This means the coil charges faster and transfers more of that energy to the spark plugs.