How to Upgrade to High Energy Ignition (HEI)

[NightFlyer]

This admittedly might be a dumb question, but I'm going to ask anyway.

By running higher voltage to the distributor, does one risk premature/accelerated wear of the impulse coil or potentially upsetting the tachometer, which I'm presuming are components that were originally designed/rated for use in a low voltage system?

[Greasy DeLorean Mechanic]

Hall effect sensor operates off whatever voltage the ECU sends out to it (12v?). Doesn't matter what the rest of the ignition system is doing -- that is all it will ever see.

Tachometer does read off the negative side of the coil, so increasing primary voltage into the coil will increase voltage into the tach, but you're only talking about a couple volts max. Remember: the coil itself has internal resistance. Later today I will try to take some measurements on the negative side of .5 ohms on the primary side versus 2 ohms.

This is all academic for you: these little cars left Dunmurry with crappy points caliber ignition, so that's the best you can do,

Bill Robertson
#5939

[Greasy DeLorean Mechanic]

I'm supposed to be making Chad's carb adapter, not fooling around with HEI deniers....

Using a 50 amp battery charger to emulate the engine running (15.6v):

Hall effect sensor gets the same voltage no matter how the resistor grid is wired: .62-.64 volts (I guess it would be .54-.55v with the alternator charging).

Pertronix coil has 2 ohms internal resistance.

Negative side of a Pertronix coil is 1.47v with both resistors in series (1.27v with the alternator charging), 1.78v with both resistors in parallel (1.54v with the alternator charging).

Bill Robertson
#5939

[Boo]

My summit racing 60,000 volt coil came with a resistor, but I didn't use it. I still have it in the tool chest though. Figured I'd hang onto it as a souvenir. I just couldn't resist.

[Greasy DeLorean Mechanic]

Are you running any resistance into the coil, or full charging voltage? Wolf on Talk is running full charging voltage. Andrei in Italy is running full charging voltage and he's bypassed the resistor inside the rotor button.

Bill Robertson
#5939

[Boo]

I honestly do not know, it does run good and fast though! I can snap a pic if you are curious.

You mean Wolf with the 'nasty' KYB shocks? LOL

[Greasy DeLorean Mechanic]

Any further comment from me would be redundant:

AMCDuraspark.jpg

Bill Robertson
#5939

[Greasy DeLorean Mechanic]

Hall effect sensor gets the same voltage no matter how the resistor grid is wired: .62-.64 volts

This is Duraspark output. Bosch module sends about 2 volts through the distributor windings.

Bill Robertson
#5939

[Andrew]

I have been researching the Duraspark module with plans to carry a spare in my cubby along with wiring instructions and tools to perform a roadside swap if necessary. While searching online I have found "49 State" modules and "CA only" modules. Normally, I would avoid "CA only" parts due to the generally correct presumption that "CA only" = Less HP. However, from what I discovered on Ford truck forums, the "CA Only" modules were intended for use in applications with higher input voltage input to the coil. Thus, could this be an exception where a "CA only" part might be better than a 49 state part???

[Greasy DeLorean Mechanic]

To be brutally honest it probably doesn't make a hill of beans difference. For example, there's no discernible difference just switching from a Bosch module to a Ford module (remainder of ignition unchanged). Generic parts house ignition modules only cost $25 -- why not buy one of each and experiment.

#1 reason to upgrade to domestic ignition, Ford or General Motors, is ease of replacement should it ever become necessary. While it is true the Bosch module is a low failure item, the damn things do go bad. Steve and Chad just had to replace Jim's Bosch module. Even OEM Ford modules fail (I lost my service truck's factory original module a year or two ago). Seems hopelessly optimistic to me to blithely assume that a 30 year old electronic module will never fail: 30 year old alarm clocks fail, 30 year old microwaves fail, 30 year old DVD players fail, 30 year old watches fail, 30 year old computers fail, etc, and they are generally kept in climate controlled environments.

Bill Robertson
#5939