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On stock HEI distributors they are included under the cap near the module. Thumpernow probably included them because they were part of the distributors he used to get the parts from.
Now as to their effect, I did some research. Since the capictor is connected between V+ and ground it appears that it might be an electro static discharge shunt; absorbing a high voltage spike send backwards into the module.
I searched google groups and found people saying it could be an RF filter or a shunt; no one was definitive on the subject. I would say that since Thumpernow had access to them and saw how they were wired in the OEM application it was good of him to include them in the XS application. I have run my HEI modules on the test bench at 10,000 rpms firing a coil without the capacitor, and watched the module waveform and didn't see a lot of noise in the wave (my scope is a very old tek that I'm only kind of proficient with though, so I might have missed it).
Here's a question though - when I did my testing I recorded the spark and posted it to this website which some may have seen; what I didn't post however was something else. When I clamped the coil + line to my bench battery the spark was like you see in the picture. when I HELD the coil + to the battery with my finger the spark was MUCH bigger ( it arced almost an inch).
What explains this? Is it capacitance in my body, is it a connection to earth ground?
Dan
Now as to their effect, I did some research. Since the capictor is connected between V+ and ground it appears that it might be an electro static discharge shunt; absorbing a high voltage spike send backwards into the module.
I searched google groups and found people saying it could be an RF filter or a shunt; no one was definitive on the subject. I would say that since Thumpernow had access to them and saw how they were wired in the OEM application it was good of him to include them in the XS application. I have run my HEI modules on the test bench at 10,000 rpms firing a coil without the capacitor, and watched the module waveform and didn't see a lot of noise in the wave (my scope is a very old tek that I'm only kind of proficient with though, so I might have missed it).
Here's a question though - when I did my testing I recorded the spark and posted it to this website which some may have seen; what I didn't post however was something else. When I clamped the coil + line to my bench battery the spark was like you see in the picture. when I HELD the coil + to the battery with my finger the spark was MUCH bigger ( it arced almost an inch).
What explains this? Is it capacitance in my body, is it a connection to earth ground?
Dan
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