On the .035 gap for HEI issue, you are thinking it lessens the number of variables but what is not computing to me is that to set up any HEI test, you are changing coils, removing ballast resistor, installing the HEI module, etc. So I don't understand why .035 HEI gap, which is totally incorrect for its operation is going to tell us anything.
Think of it as one system compared to another system not the total parts and you are testing one variable.
We know that the HEI puts out a higher voltage. We do not know how much the larger spark plug gap adds to making the HEI better. Testing with the .035 gap with SI and then HEI allows us to test the one part that is common to both systems and we then can see how much importance SP gap has on how HEI functions.
If you had a Sun Distributor machine and an Analog Oscilloscope you could observe how secondary voltages change, see how RPM's effect timing advance curves and compare systems. I do not have or know how to use a Sun Distributor machine. My dad did and I still have a box filled with distributor weights and advance springs. And memories of my dad saying how with that box he could set up distributors to get maximum performance from an engine.
You do have the ability to test HEI at .035 and .040 to gain insight where HEI provides the effect.
I REALLY only want to do two gaps on each style ignition. To add three more tests really seems like alot for something that nobody will ever do. It isn't comparing apples to apples due to the coil change.
Again this is a test of SI system and HEI system not a test of individual parts.
On the throttle issue.. Im still confused. Idle is (for example) 650 RPM. It's 650 RPM using the stock ignition and its STILL 650 RPM using HEI. Since I am starting with the stock ignition and it's weaker, I set the throttle for 650 RPM. When I go to the HEI I set the throttle for 650 RPM. What does the throttle movement differences tell us?
It is one thing to prove HEI has lower SFC. By measuring the fuel used all you can prove how much fuel was used. You can not prove why SFC changed.
By noting HEI used less fuel by throttle position changes then you are proving that the superior spark of HEI is the reason for improving SFC. Not that just SFC got better.
I will NOT be changing ANY controls on the carb for these tests. That is messing with a control. Before testing I will make sure I can get down to 550 RPM just to make sure I have the ability to control the RPM in the range I want using both ignitions.
Turning the Idle Speed screw to make sure HEI runs at the same RPM's is not messing with any controls. The idle speed adjustment is not the idle mixture adjustment. Knowing how much the Idle Speed screw is turned to achieve the correct RPM provides a mechanical indication of how much the HEI allows the throttle to be closed and get the same RPM's.
Does that make sense? Or do you think it's okay to re-optimize the carbs idle circuit for each ignition? The idea was to see how changing just the ignition system would affect fuel consumption. Sincerely, thank you for the help.
No, put down that screwdriver and slowly back away from the Idle Mixture Screw. Touching the mixture screw is only adding variables to the test. Can HEI allow for leaner Idle Mixture settings, most likely some. But then you would be needing to start another whole level of tests. Best to keep things simple for now.
