Questions about electronic vs HEI

RustyRatRod said

Why is a hotter/higher voltage spark needed anyway? I'll tell you the only reason.

As compression and cylinder pressure goes up, the plug has more resistance to spark. That is the only one reason why extra spark is needed.

So, if you have a lower compression ratio and or lower cylinder pressure (a stock or mild engine) you don't need the extra spark from HEI, so it is merely bragging rights.

Click to expand...

There is another factor to consider in the spark voltage and energy needed to properly ignite the mixture, and that is the A/F mixture ratio itself. It is a combination of both compression/pressure AND A/F ratio that determines the needed voltage/energy of the spark. So even a low compression engine will have times when the mixture is harder to properly fire, whenever the A/F changes a certain way.

With carbs, they tend to 'approximate' the proper A/F ratio but it will vary a LOT more around the ideal A/F ratio with a carb than with EFI. So there is a very real the benefit of HEI with any engine in properly firing the full range of operating A/F ratios AND pressures, even in low compression engines.