I work in electrical engineering. I changed my 1970 200 cid distributor to a 1976 Duraspark distributor; and modified the control box (gutted) for a GM HEI control module. The signal from the distributor's reluctor/pick-up coil is weak (as trigger signals go), so the longer you make that line, the more attenuated the signal will be and more susceptical to electrical noise (false triggering). Also, the lines back to the ignition coil are high current: creating magnetic fields around the conductors that can couple into other things (radios, tach. the pick-up coil.etc.) And, again, the longer the length, the more the loss.
I was just wanting to remove some of the clutter from under the hood, but after reading Greg's post I may just leave it there. I was also planning to relocate the battery, starter solenoid, and possibly updating the alternator to use an internal regulator. Greg, what is the benefit to the GM HEI module?
Duraspark vs HEI Good question. The Duraspark offers a unique feature that the HEI does not. The white wire from the Duraspark connects (can be connected) to the starter relay, to retard the ignition, during starting. The OEM Duraspark module is no longer offered - though, there are plenty of "after market" modules available (NAPA, etc.) The HEI is robust, produces a very "hot" spark, very reasonably priced, and easy to replace - "on the fly" I connected both the (origional) ignition wires coming from the key-switch together. and connected to one side of a relay coil. The other side is connected to ground. One side of the relay contacts is connected to the battery, through a fuse. The other relay contact (output) is connected to the HEI module and the + side of the ignition coil. So the ignition coil gets full battery potential.
PS: There is a 7-pin HEI Module that includes syphistcated timing features, but the electronics to control it is beyond the scope of "Everyman".
There are three actually lol one you ground and two you apply voltage to, I don't have the part number but I asked for one from a 1980 Oldsmobile with the 260 I believe. I can get you a picture of it if you want, It's the one you ground it pulls 10 degrees of cam timing I believe, so 5 real degrees I wouldn't know of it either if I hadnt needed it for budget spark retard for my turbo project, and a friend in my IEEE group hadnt mentioned it
Thre 3 Three Oh...you mean these three: There were three different versions of a five-terminal module system, and the modules 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. The point you made is very important. The retard is for a turbo boost....not cranking over. In fact, the #1 you are talking about cuts the coil output, too.
:Handshake Yes, I mean the five pin GM modules you found information on haha, and actually it was originally used FOR starting, probably using a relay or similar to ground it out while cranking at least from my understanding since those oldsmobiles werent boosted This wasn't meant as a hit, just to point out that in this ONE case, GM has basically everything we could need from a part, without going aftermarket
This whole thing actually is making me want to build my own box to use the tach signal to control the voltage to the ICM based on my own rules
Retard ! Do it "on the cheap" with an LM555 timer IC = frequency to voltage converter: http://www.circuitstoday.com/f-to-v-converter
