'74 Dart, 225 /6, A904. Doing the GM HEI conversion per the slantsix.org instructions. http://www.slantsix.org/forum/viewtopic.php?t=15779 My intention is to install it on the passenger fender, use the original switched 12v at the OEM ignition circuit, and put my full 12v from the alternator stud. I want to leave all the original ignition components and circuitry intact so if anything ever happens I can just unplug the HEI from the distributor and plug the original ignition back in and be mobile until I can fix what's wrong. In the article, he mentions to just connect the 2 wires at the ballast resistor together. I'm assuming he's working with the older model that only has 2 terminals at the ballast resistor. My '74 has the newer 4 terminal configuration. Do I need to anything with it, connect the 2 lefts to the 2 rights as they sit, do nothing at all, or what? All input is greatly appreciated!
GM HEI conversion - what to do with ballast resistor?
- Thread starter sargentrs
- Start date
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Pete in NH
Well-Known Member
HI,
How much of the original system are you planning to leave intact? If you leave the original coil in place and use a new coil with the HEI system, you can leave the original ballast resistor in place. You could simply unplug the old Mopar ECU to disable the original system and move the HV coil wire over to the new coil. Also, you will need to move the distributor pick up wire between systems. I would power the new HEI system through a relay. The relay would be energized by the blue wire on the ballast resistor and one side of the relay would go to the alternator output stud through a fuse. The other side of the relay would go to the new HEI system.
How much of the original system are you planning to leave intact? If you leave the original coil in place and use a new coil with the HEI system, you can leave the original ballast resistor in place. You could simply unplug the old Mopar ECU to disable the original system and move the HV coil wire over to the new coil. Also, you will need to move the distributor pick up wire between systems. I would power the new HEI system through a relay. The relay would be energized by the blue wire on the ballast resistor and one side of the relay would go to the alternator output stud through a fuse. The other side of the relay would go to the new HEI system.
I was considering relocating the coil to the fender also anyway so that's a good idea! I bought a connector with pigtails similar to the distributor pickup but I'm not sure if it fits yet or not. I'm also using a relay as you mentioned. The way I've got it mapped out, I should be able to easily swap to the original system if the HEI fails. My original wiring is full of gremlins right now and I'm still trying to sort it all out. I'm not a purist (please don't hate on me) and she's more of a ratrod than anything else, just my daily driver. After the HEI I'll start prepping for the Denso alternator mod. I've already done the bulkhead/ammeter bypass because of a melted bulkhead. Couple more things and my original wiring will only be carrying minimum electrical loads. Thanks for the advice, Pete!
BillGrissom
Well-Known Member
Connect the +12 V terminal (one w/ jumper wire) to the terminal going to coil+ (usually blue wire, but check wiring diagram). You don't need to connect the terminal for ECU power since you aren't powering your factory ECU. I use a male-male spade, but could use a short jumper wire.
One more quick question. In Dan's article, he mentions..
"Which pickup coil wire goes to which module terminal is determined by trial and error: If engine is difficult to start or runs poorly after installation, you swap these two wires."
Anybody know for sure which one goes to which? Wire colors are faded but the '73 diagram I have say they're gray and brown. I can tell it's a light colored wire and a dark colored and the module terminals are labeled W and G. I'd like to pre-fab the harness so it'd be nice to get it right the first time. Thanks for all the help!
"Which pickup coil wire goes to which module terminal is determined by trial and error: If engine is difficult to start or runs poorly after installation, you swap these two wires."
Anybody know for sure which one goes to which? Wire colors are faded but the '73 diagram I have say they're gray and brown. I can tell it's a light colored wire and a dark colored and the module terminals are labeled W and G. I'd like to pre-fab the harness so it'd be nice to get it right the first time. Thanks for all the help!
HEI module is hooked up, via relay, and hooked in new coil, moving coil wire off of the original coil to the new one. I think I've covered all the bases but she won't start/run, just turns over. I ran my 12v input source to the alternator output stud, through a fuse, and to the relay. My "trigger" source is the the blue wire at the ballast resistor, disconnected from the resistor. With key on, I have 12v input from the alternator, 12v in to the trigger, 12v out to the B terminal on the module and 12v at the coil +. Ground on the module mounting screw checks out at 0 resistance with the battery negative. Same with relay ground. Tried swapping the W and G terminals on the module for the distributor pick up but still wouldn't start.
Had trouble getting the negative wire off of the original coil, hole in ring terminal's a tight fit on the stud, so left it there for now. Fought it for 5 minutes, big hands, fat fingers, tight quarters. Could this be causing an issue? Did totally disconnect the + terminal.
First attempt at start, the inline 15A fuse from the alternator source fried. Put a new fuse in it and tried again. Fuse held but no start. Should I run 12v input to relay from the battery instead of the alternator output?
What kind of readings should I get at the W and G terminals on the module?
Hooked original ignition back up and she starts and runs fine. Any ideas? Gotta run pick up the grandkids from school so no more troubleshooting till the morning. Any and all input is greatly appreciated!
Had trouble getting the negative wire off of the original coil, hole in ring terminal's a tight fit on the stud, so left it there for now. Fought it for 5 minutes, big hands, fat fingers, tight quarters. Could this be causing an issue? Did totally disconnect the + terminal.
First attempt at start, the inline 15A fuse from the alternator source fried. Put a new fuse in it and tried again. Fuse held but no start. Should I run 12v input to relay from the battery instead of the alternator output?
What kind of readings should I get at the W and G terminals on the module?
Hooked original ignition back up and she starts and runs fine. Any ideas? Gotta run pick up the grandkids from school so no more troubleshooting till the morning. Any and all input is greatly appreciated!
mopower440
Well-Known Member
Make sure the GM HEI module itself is grounded! If its not, she wont run..
I thought I had it grounded well through the inner fender. Even cleaned the surface underneath down to shiny metal and used star washers. I'll fab a ground wire to the relay ground tomorrow and see if that does it. Thanks for the tip!
Pete in NH
Well-Known Member
Hi,
I'm concerned that the 15 amp fuse blew on your first attempt, 15 amps should have held just fine on an ignition system. I would leave the 12 volt source wire on the alternator output stud, otherwise the ignition system current will look like battery charge current on your ammeter if connected to the battery. I would want to know why that fuse blew. Check that the HEI module is grounded well but, there may be a wiring error. Could you post some pictures of your installation or a good diagram of how you have things wired up? I could be a big help in seeing what is going on.
I'm concerned that the 15 amp fuse blew on your first attempt, 15 amps should have held just fine on an ignition system. I would leave the 12 volt source wire on the alternator output stud, otherwise the ignition system current will look like battery charge current on your ammeter if connected to the battery. I would want to know why that fuse blew. Check that the HEI module is grounded well but, there may be a wiring error. Could you post some pictures of your installation or a good diagram of how you have things wired up? I could be a big help in seeing what is going on.
Got it running now but will go ahead and document everything here and describe what I think was wrong.
First I took a piece of 1/4" aluminum and cut it to about 2" x 3". I located and drilled two 3/16" holes to match up to the mounting holes in the module. Then took the plate and located and drilled matching holes in the passenger fender. I used a wire wheel on my drill and cleaned the underside of the fender to shiny metal. Using #8-32 x 1" machine screws, star washers and lock nuts, I bolted the module (Standard # LX301) to the inner fender.
I purchased a 12v 4 pole relay and mounted it beside the module. I held in place with a sheet metal screw and drilled a 5/16" hole in the fender for a ground wire. Also cleaned both sides of the fender to shiny metal. Then I mocked up my harness.
Once I verified length and terminal connections, I made my harness with connections like this:
1. Relay post # 85 to 12v switched source at blue wire connector for ballast resistor.
2. Relay post # 30 to alternator output stud through 15A fuse.
3. Relay post # 87 to splice joining "B" terminal on module and coil + terminal.
4. "C" terminal on module to coil - terminal.
5/6. "W" and "G" terminals on module to distributor pick up pigtail.
7. Relay post # 85 to ground through fender with star washers and bolt/nut.
After installing the module (with thermal grease) and the relay, I mounted another coil also on the fender. My intention is to keep the original ignition system intact and have the HEI system separate so I can swap easily between the two systems if somethings goes wrong.
Also rigged a jumper wire, disconnected the ballast resistor wiring, connected the top two wires together and left the bottom two hanging loose. I added another jumper as my 12v switched source to trigger the relay. Getting full 12v source power from the alternator output stud.
Later came back and added a separate ground wire from the module to the relay ground bolt.
1. Relay post # 85 to 12v switched source at blue wire connector for ballast resistor.
2. Relay post # 30 to alternator output stud through 15A fuse.
3. Relay post # 87 to splice joining "B" terminal on module and coil + terminal.
4. "C" terminal on module to coil - terminal.
5/6. "W" and "G" terminals on module to distributor pick up pigtail.
7. Relay post # 85 to ground through fender with star washers and bolt/nut.
After installing the module (with thermal grease) and the relay, I mounted another coil also on the fender. My intention is to keep the original ignition system intact and have the HEI system separate so I can swap easily between the two systems if somethings goes wrong.
Also rigged a jumper wire, disconnected the ballast resistor wiring, connected the top two wires together and left the bottom two hanging loose. I added another jumper as my 12v switched source to trigger the relay. Getting full 12v source power from the alternator output stud.
Later came back and added a separate ground wire from the module to the relay ground bolt.
Originally, after mounting the module and relay, I hooked up the module to the distributor pick up connector and connected the module to the original coil, in place. After cranking it and her not starting, I found out the fuse from the alternator to the relay had fried. Put another fuse in, tried again but still no start. However, the fuse remained good. Thought maybe it might have grounding issues so added the separate ground wire to the module. Still no start.
Loose mounted the new coil on the fender and ran the wiring to it instead instead of the original coil. Still no start. Tried running a jumper from the battery straight to the new coil + and she fired right up. However, she would die until I removed the wire. So I figured everything was pretty much good with the module and the wiring. I had read conflicting information about having to wire in the original coil + wire in addition to the "B" terminal wire to the coil. So I made up a jumper and tried it. She fired right up, idled smoothly and revved great. Made a permanent connection from the original coil + to the new coil + and now she starts, runs and kills perfectly. Still gotta go back and install new 8mm wires, new distributor cap/rotor and regap the plugs but I can already tell she's running smoother.
As a side note, I knew I had issues with my original ignition wiring. The 8 pin plug connecting the ignition harness, at the firewall, behind the valve cover, occasionally gets an intermittent loss of connection and I have already repaired several of the PO's multiple wiring sins. A fried bulkhead connector caused to do the ammeter bypass/alternator wiring mod which helped another intermittent start issue. I have installed an aftermarket voltmeter to monitor my voltage. Running at idle, voltage would drop down to 12v or slightly less and with lights and heater on, I have to keep it revved up to about 800 rpm to keep the battery charging. Now, after the HEI installation, eliminating the original igntion circuit, I get an even and steady 14+ volts at idle with mild fluttering of the gauge and a rock steady 14.5 volts on the road. Even turning on the lights and the heater only affect it minimally, bringing it down to about 13v. Obviously, I have some serious wiring problems under the hood. Overall, I'm very happy with the results.
Loose mounted the new coil on the fender and ran the wiring to it instead instead of the original coil. Still no start. Tried running a jumper from the battery straight to the new coil + and she fired right up. However, she would die until I removed the wire. So I figured everything was pretty much good with the module and the wiring. I had read conflicting information about having to wire in the original coil + wire in addition to the "B" terminal wire to the coil. So I made up a jumper and tried it. She fired right up, idled smoothly and revved great. Made a permanent connection from the original coil + to the new coil + and now she starts, runs and kills perfectly. Still gotta go back and install new 8mm wires, new distributor cap/rotor and regap the plugs but I can already tell she's running smoother.
As a side note, I knew I had issues with my original ignition wiring. The 8 pin plug connecting the ignition harness, at the firewall, behind the valve cover, occasionally gets an intermittent loss of connection and I have already repaired several of the PO's multiple wiring sins. A fried bulkhead connector caused to do the ammeter bypass/alternator wiring mod which helped another intermittent start issue. I have installed an aftermarket voltmeter to monitor my voltage. Running at idle, voltage would drop down to 12v or slightly less and with lights and heater on, I have to keep it revved up to about 800 rpm to keep the battery charging. Now, after the HEI installation, eliminating the original igntion circuit, I get an even and steady 14+ volts at idle with mild fluttering of the gauge and a rock steady 14.5 volts on the road. Even turning on the lights and the heater only affect it minimally, bringing it down to about 13v. Obviously, I have some serious wiring problems under the hood. Overall, I'm very happy with the results.
BillGrissom
Well-Known Member
When you get a chance, twist the 2 wires to your distributor pickup. Otherwise, you can get "self-excitation" if the pickup senses the current spikes from the sparks.
That slantsix article is a bit dated. Most today use the 8-pin HEI module w/ GM "external coil" since simpler and more robust wiring. See Megasquirt site. I did that in my 64 Valiant. TrailBeast started selling the parts new, for those who don't junkyard pick like me. So far, just tested it by spinning the distributor by hand (working other issues w/ car). Use a timing light to check for correct polarity of the pickup (should flash when teeth in distributor are aligned). The relays are a good idea. I put a whole relay/fuse box in my two early A's (see post).
That slantsix article is a bit dated. Most today use the 8-pin HEI module w/ GM "external coil" since simpler and more robust wiring. See Megasquirt site. I did that in my 64 Valiant. TrailBeast started selling the parts new, for those who don't junkyard pick like me. So far, just tested it by spinning the distributor by hand (working other issues w/ car). Use a timing light to check for correct polarity of the pickup (should flash when teeth in distributor are aligned). The relays are a good idea. I put a whole relay/fuse box in my two early A's (see post).
67dartgtgo
Well-Known Member
Curious...what do you do with the original light blue with yellow trace stripe wire that is the original full 12 volts start wire. I'm cleaning up my bay withe the HEI install based on trailbeasts and others units. I have the original harness distributor wires and negative coil wire pulled but not sure what to do with this one.
TrailBeast
AKA Mopars4us on Youtube
If you had a four wire ballast you tie it together with your "Run" wire to supply the coil with full voltage during start and run both.
If you had a one wire ballast, then that one wire would be your new coil power supply.
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