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I was trying to help someone the other day in explaining the advantages of HEI, but it always makes me feel like I am being self serving since I designed one specifically for our engines that uses your stock Distributor and works just as GM designed it to. So, I searched the Internet looking for a decent, very accurate article and found the perfect one. Here it is:
http://www.hemmings.com/magazine/mus...I/1719426.html
One of the other issues that I get asked a lot is "What is the difference between GM HEI and Pertronix?". Despite what the advertisements for Pertronix say, the units they sell are strictly 'Points Replacement' units. They have no artificial intelligence behind them. Pertronix units go inside the Distributor and replace the points and condenser. They are a great low-budget solution and they work very well. They are easy to install and they really do the job for which they were intended very well. I have heard very few complaints about them.
The difference between Pertronix and GM HEI is vast. GM HEI has artificial intelligence that makes it leaps and bounds better from a logical perspective. The GM HEI has an Electronic Ignition Module. This Module, altho quaint by today's standards, was the Grandfather of our modern Electronic Control Modules which are considered on-board computer systems. The GM HEI Module gives the system its ability to self adjust the dwell based on engine RPM. It's secondary function is to speed up dramatically the ramp and fire circuit to 3.4 milliseconds which enabled much faster coil response. What this means is, we can use hotter coils. This means a more complete burn of leaner fuel mixtures. It also has a current control circuit that keeps the amperage of the entire Ignition System down to 5.4 Amps.
Aside from the above, the GM HEI System removed the Resistor Circuit from the mix. This means no more reducing the points and condenser down to 6 volts. This was a practice right up until GM HEI was introduced in 1974. The Resistor Circuit is what that big paint melting Ballast Resistor that is on your firewall was used for. By transferring half of the available power to heat, Delco was able to keep the 6 volt production line going clear into the 1970's! The GM HEI System uses no resistors and with Transistorized current control, as stated earlier, keeps the current limited to 5.4 amps. In fact, it craves the full 12 volts of power and is much happier with a 45,000 volt, .7 ohm coil with the spark plugs gapped to .045. As stated in the above article, it really is a very well engineered system. Have a great week!
http://www.hemmings.com/magazine/mus...I/1719426.html
One of the other issues that I get asked a lot is "What is the difference between GM HEI and Pertronix?". Despite what the advertisements for Pertronix say, the units they sell are strictly 'Points Replacement' units. They have no artificial intelligence behind them. Pertronix units go inside the Distributor and replace the points and condenser. They are a great low-budget solution and they work very well. They are easy to install and they really do the job for which they were intended very well. I have heard very few complaints about them.
The difference between Pertronix and GM HEI is vast. GM HEI has artificial intelligence that makes it leaps and bounds better from a logical perspective. The GM HEI has an Electronic Ignition Module. This Module, altho quaint by today's standards, was the Grandfather of our modern Electronic Control Modules which are considered on-board computer systems. The GM HEI Module gives the system its ability to self adjust the dwell based on engine RPM. It's secondary function is to speed up dramatically the ramp and fire circuit to 3.4 milliseconds which enabled much faster coil response. What this means is, we can use hotter coils. This means a more complete burn of leaner fuel mixtures. It also has a current control circuit that keeps the amperage of the entire Ignition System down to 5.4 Amps.
Aside from the above, the GM HEI System removed the Resistor Circuit from the mix. This means no more reducing the points and condenser down to 6 volts. This was a practice right up until GM HEI was introduced in 1974. The Resistor Circuit is what that big paint melting Ballast Resistor that is on your firewall was used for. By transferring half of the available power to heat, Delco was able to keep the 6 volt production line going clear into the 1970's! The GM HEI System uses no resistors and with Transistorized current control, as stated earlier, keeps the current limited to 5.4 amps. In fact, it craves the full 12 volts of power and is much happier with a 45,000 volt, .7 ohm coil with the spark plugs gapped to .045. As stated in the above article, it really is a very well engineered system. Have a great week!
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