Interesting HEI article
Thread Starter
Burning Brakes
Joined: Jun 2004
Posts: 936
Likes: 0
From: Tulsa OK
Interesting HEI article
I came across this trolling around for information on HEI distributors and thought some might find it useful, or at least informative. You can never have to much info, right? 
http://reviews.ebay.com/HEI-Ignition...00000002053885
Enjoy!
http://reviews.ebay.com/HEI-Ignition...00000002053885
Enjoy!
Race Director
Joined: Jun 2000
Posts: 10,039
Likes: 669
From: FL
I found this part interesting:
The first type sounds like something that could be used to retard the spark when you hit the nitrous (depending on the amount of spark retard). I would love to find out more about these modules.
There were three different versions of a five-terminal module, and they aren't interchangeable with one another. In each case, the fifth terminal was used to accept a signal that the module processed in order to retard the timing. All the "5-terminal" modules are used with distributors having conventional centrifugal and vacuum advance mechanisms.
1. HEI/EMR Electonic Module Retard uses a wire connected to a switch or to an electronic control package. Under certain conditions, the switch or control package will ground the wire, which triggers the retard feature built into the distributor module.
2. HEI/ESC Electronic Spark Control uses a knock sensor and an electronic controller. The knock sensor sends a voltage signal to the controller, which sends a voltage signal to the distributor module, activating the retard feature within the module.
3. HEI/ESS Electronic Spark Selection uses an outboard electronic decoder which receives voltage signals from three sources: a manifold pressure switch, the distributor pickup coil, and an engine temperature switch. The decoder processes the information and provides a voltage signal to the distributor module to adjust the amount of advance/retard.
1. HEI/EMR Electonic Module Retard uses a wire connected to a switch or to an electronic control package. Under certain conditions, the switch or control package will ground the wire, which triggers the retard feature built into the distributor module.
2. HEI/ESC Electronic Spark Control uses a knock sensor and an electronic controller. The knock sensor sends a voltage signal to the controller, which sends a voltage signal to the distributor module, activating the retard feature within the module.
3. HEI/ESS Electronic Spark Selection uses an outboard electronic decoder which receives voltage signals from three sources: a manifold pressure switch, the distributor pickup coil, and an engine temperature switch. The decoder processes the information and provides a voltage signal to the distributor module to adjust the amount of advance/retard.
Instructor
Joined: Jun 2006
Posts: 146
Likes: 5
From: North Brunswick New Jersey
I found this part especially interesting, as I have been chasing ways to make my dist. correct. Does anyone have experience with this that can elaborate more on the subject?
SPECIAL IMPORTANT NOTE #3
I have seen excessive "hidden" centrifugal advance when the center plate is installed "wrong". That is, you may think you have a normal, proper centrifugal advance, and that it stops advancing at or around 2500--3000 rpm. But if you rev higher, it will begin advancing again at 4000-4500 rpm. That "hidden" advance--perhaps an additional 5--10 degrees--at best will reduce performance and perhaps cause ping--at worst it will destroy your engine. I have seen this on EVERY GM center plate I've checked when the weights are acting on the gently rounded part of the center plate. If you flip the center plate upside down, so the weights act on the dogleg curve part, the advance will positively stop at a given RPM dependant on the weights and the shape of the center plate. The numbers stamped into the center plate may face up or face down. Either way "can" be correct, depending on the direction of rotation of the distributor.
SPECIAL IMPORTANT NOTE #3
I have seen excessive "hidden" centrifugal advance when the center plate is installed "wrong". That is, you may think you have a normal, proper centrifugal advance, and that it stops advancing at or around 2500--3000 rpm. But if you rev higher, it will begin advancing again at 4000-4500 rpm. That "hidden" advance--perhaps an additional 5--10 degrees--at best will reduce performance and perhaps cause ping--at worst it will destroy your engine. I have seen this on EVERY GM center plate I've checked when the weights are acting on the gently rounded part of the center plate. If you flip the center plate upside down, so the weights act on the dogleg curve part, the advance will positively stop at a given RPM dependant on the weights and the shape of the center plate. The numbers stamped into the center plate may face up or face down. Either way "can" be correct, depending on the direction of rotation of the distributor.
