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Discussion Starter · #1 · (Edited)
Hey RCC!

Ok, I'm hoping someone can explain this like you would to a 5 year old.

1975 TD, 318 engine, A833 4 speed trans, I'm about to install a Holley Sniper complete kit.
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I'm trying to figure out what wires I can remove from my ignition (and running) system, that won't be needed with the Holley set up.

How do these 3 pieces tie together? And if 1, 2, or all 3 of them are eliminated then how do I wire it to make it functional? I know the ballast resistor and the ECU work together somehow, but I don't know if you eliminate 1 then how that effects the other.
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Also, some of the wires go back to the bulkhead connector below (circled in red). #17-24 are the corresponding connections (thanks to Dean). I'm really only concerned with #22-24 and where they would go if I no longer have the pieces above.
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Or, if someone knows of a website that explains it all to the layman, please let me know.

Thanks for any replies.
 

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I'll give it a quick shot.

Yes, 1 and 2 go together. 1 Gives reduced voltage to the coil while the engine is running, so it does not run too hot. It is bypassed when starting to give a hotter spark.

2 is the brain for the ignition. Both can go when you convert to the sniper.

3 is the voltage regulator, controls the alternator.

From memory, 22 is the red wire you see on all three pieces. You will need to keep it for the voltage reg to work. Might be able to use it for the sniper, but it is not powered when the engine is cranking (Another circuit gives power when cranking to 1, and 2). 3 stays off when cranking, to prevent voltage spikes while the alternator spins up to speed.

Unless you have a factory tach, you likely do not have any wire in slot 21.

23 you need to keep, it also gives power to the inside of the cab, goes to one side of the alt gauge.

24 I will have to look up before I say for sure.
 
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Discussion Starter · #3 ·
I'll give it a quick shot.

Yes, 1 and 2 go together. 1 Gives reduced voltage to the coil while the engine is running, so it does not run too hot. It is bypassed when starting to give a hotter spark.

2 is the brain for the ignition. Both can go when you convert to the sniper.

3 is the voltage regulator, controls the alternator.

From memory, 22 is the red wire you see on all three pieces. You will need to keep it for the voltage reg to work. Might be able to use it for the sniper, but it is not powered when the engine is cranking (Another circuit gives power when cranking to 1, and 2). 3 stays off when cranking, to prevent voltage spikes while the alternator spins up to speed.

Unless you have a factory tach, you likely do not have any wire in slot 21.

23 you need to keep, it also gives power to the inside of the cab, goes to one side of the alt gauge.

24 I will have to look up before I say for sure.
SuperBurban, thanks for the info.

Regarding wire #23, the large black to/from the alternator. I am going with after market gauges, so will be converting to a volt meter (getting source from a 12v wire), so my plan is to run #23 to a bus bar and connect it to the other large red wire that was also on the original alt gauge, which will make the connection from the battery (via starter relay) to the alternator. I think I've got that right.

#22 is still a question mark for me. Does the alternator need to have the VR connected, no matter what? If yes, then I guess it will go straight from the bulkhead #22 to the VR (assuming I've eliminated the ballast resistor and ECU).
Does it tell the alternator when to start/stop to maintain voltage?

Thanks again.
 

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'79 Macho 360 Magnum, Comp 480 cam, Hughes springs, 650 Thunder AVS, Pertronix Flamethrower ignition
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When I went to the Pertronix system I had my buddy chop the wires to the ballast and the ECU because I no longer need them but I can't remember which wires. I'm sure it's just the 4 wires to the ballast and the 5 wires to the ECU. Looks so much clearer even though I've added a few relays (with the engine in place of course).
 

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SuperBurban, thanks for the info.

Regarding wire #23, the large black to/from the alternator. I am going with after market gauges, so will be converting to a volt meter (getting source from a 12v wire), so my plan is to run #23 to a bus bar and connect it to the other large red wire that was also on the original alt gauge, which will make the connection from the battery (via starter relay) to the alternator. I think I've got that right.
Yes, that is right
#22 is still a question mark for me. Does the alternator need to have the VR connected, no matter what? If yes, then I guess it will go straight from the bulkhead #22 to the VR (assuming I've eliminated the ballast resistor and ECU).
Does it tell the alternator when to start/stop to maintain voltage?

Thanks again.
22 is the same circuit going to all three. You need to keep it going to the voltage reg, and the alt. You need both for the alt to work. Yes, simple terms it tells the alt to start & stop. It may also feed a choke heater if you have that. Maybe any emissions stuff, but I do not think it would on your 75.

That 12V switched source might be the hard one to find. IIRC, all the circuits from the ign switch turn off when cranking. The ign module gets power from the start circuit when cranking, and then the ign (number 22), wire when you let off the key. I had to get fancy with a relay to power my HEI distributors.
 

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You're on the right track and I'll be doing the same at some point in time. When I begin my EFI journey, I'm going to remove my engine harness and make one to fit. I spent YEARS finding correct, good condition, un molested wiring along with some NOS sections which is why I'm going to go about it the hard way.
 
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