The HEI puts out plenty voltage for a strong spark, thats for sure. But the spark timing at different RPM (advance curve) is even more important than raw output. The spark has to happen at the right time to make max power with a modified engine.
The stock HEI advance curve usually gives 17 to 20 degrees maximum advance. Thats pretty short (not much advance) This means that you'll get base + 20 for total timing. The advance curves were shortened when HEI came out, cuz HEI came out during the smog wars, when engines were designed to run lean with low compression ratios and poor fuel. Running an aggressive curve on these engines wouldn't help them much from the factory.
For example, lets say your engine needs 38 degrees total at 3 grand. Well, subtract 20 degrees from that and thats 18 degrees BTDC at idle. Thats usually too much base timing. So if you back off the base timing so she'll start and idle, you don't get enough advance at higher RPM. The motor's response can be sluggish, sloppy and inefficient. The engine can run hot and use more fuel.
Usually re-curving a distributor is done by replacing the center plate, weights and springs. The shape of the center plate controls maximum amount of advance. The moroso kits provide weights and a matched center plate that lets the weights travel further and give more advance. The springs set the RATE of advance.
In my pontiac, I removed my center plate and reshaped it with a grinder to provide more travel. Careful to not remove too much material, as you'll get too much advance travel at really high RPM. (more a problem on high comp V8.) Now my car will smoke first and chirp second. No kidding!
Extreme example. For a NOS application, you must retard the timing 2 degrees for every 50 HP shot of NOS. So if you're running a 150 shot, you've got to retard the timing 6 degrees. 6 DEGREES! Thats the differance between winning a race and scattering a motor.
You really would be amazed how properly recurving a dist will help the crispness of engine response and mileage.
