Battery relocation/ NHRA kill switch/MSD 6AL Wiring help needed.

[DusterJoe410.4]

May dad and I are working on wiring up my 71 duster street/strip car and we are trying to figure out how to wire everything up and be legal to run it at any NHRA track. I have a stock style Mopar alternator with 2 field wires and the main power lead, a 4 pole kill switch, and a MSD Digital 6al ignition box.

The first thing we are trying to figure out is what to do for the alternator kill side of things because the the big wire from alternator wire runs directly to the amp meter and we are still planning to running it for the time being. This is the first time we’ve set a car up with a kill switch so we are in sure of ho to make it all function properly.

Secondly the blue field wire from the alternator runs to the ballast resistor but we are deleting because the msd box doesn’t need on and will power the coil on its own. So we are trying to trying to decide if we can just delete the ballast resistor or if we should just leave it and delete the coil wire from it and keep the rest the way it was from the factory

 

[67Dart273]

There's a "several" ways to do this. So far as the MSD, you can hook the ballast wires together, then take the original coil+ wire and route that to the "small red" of the MSD which triggers the system "on." Main power "big red' goes to hot at all times

So far as the kill switch, I would add a relay to run the engine bay VR/ etc. This is to reduce voltage drop which causes overcharging, and will fit right in with your kill switch

Cut the blue "ign1" "run" wire coming out of the bulkhead. Use the firewall end to trigger a relay. Feed the relay contacts with a fuse/ breaker (say 20A) and mabye no14 or 12 off the starter relay stud. Now for the kill switch. Run two no1 4's up front from the disconnect. Connect them in series with the blue "run" wire triggering the relay coil. Ground other end of coil. Hook the engine bay end of the "run" wire to the NO contact

So pulling the disconnect will drop out the relay and kill both the ignition and the alternator. Nothing can "run on" with that setup

So in the end you cut the blue "run." wire. Firewall / bulkhead end connects to one wire from the small terminals on the disconnect. Other wire from disconnect connects to 86, which is the relay coil, and ground 85, other end of coil

Feed fuse/ breaker power from starter relay stud to 30

Connect the engine bay end of the blue "run" wire to 87

 

[Goonchannel]

67Dart 273, I’ve been trying to find a way to contact you to get your opinion on my setup. Please send me a private message (I can’t figure out where to do that. Is it called that or “start conversation”?

 

[Demonracer]

Start conversation is the old private message.

 

[Mattax]

Secondly the blue field wire from the alternator runs to the ballast resistor but we are deleting because the msd box doesn’t need on and will power the coil on its own. So we are trying to trying to decide if we can just delete the ballast resistor or if we should just leave it and delete the coil wire from it and keep the rest the way it was from the factory

The MSD on/off wire carries so little current it doesn't matter if the ballast resistor is there or not.
You can leave it as is if you want, or put a jumper across it with piggy back terminals. Or you can remove it. Completely up to you.

The first thing we are trying to figure out is what to do for the alternator kill side of things because the the big wire from alternator wire runs directly to the amp meter and we are still planning to running it for the time being. This is the first time we’ve set a car up with a kill switch so we are in sure of ho to make it all function properly.

Here's a diagram of a way to use a relay to interupt as 67Dart273 was describing.
This is from a previous thread about a disconnect with battery in the trunk, but reworked to show an MSD and working ammeter.

When the key is off, there is no power to the ignition or to the alternator's rotor.
When the master disconnect is open, there is no power to the ignition or the alternator's rotor.

If you want to keep the ammeter in operation, but take the recharging load off of the multiconnector in the bulkhead, then run another wire through a grommet to the ammeter.

 

[Mattax]

Or same concept as above with both wires through a grommet like a 'fleet' alternator wiring setup.
In this case the guy was planning on an engine compoartment and a trunk battery, but of course still needed to cut off power from the trunk.

 

[67Dart273]

67Dart 273, I’ve been trying to find a way to contact you to get your opinion on my setup. Please send me a private message (I can’t figure out where to do that. Is it called that or “start conversation”?

Yes

 

[DusterJoe410.4]

The MSD on/off wire carries so little current it doesn't matter if the ballast resistor is there or not.
You can leave it as is if you want, or put a jumper across it with piggy back terminals. Or you can remove it. Completely up to you.




Here's a diagram of a way to use a relay to interupt as 67Dart273 was describing.
This is from a previous thread about a disconnect with battery in the trunk, but reworked to show an MSD and working ammeter.
View attachment 1715755114


When the key is off, there is no power to the ignition or to the alternator's rotor.
When the master disconnect is open, there is no power to the ignition or the alternator's rotor.

If you want to keep the ammeter in operation, but take the recharging load off of the multiconnector in the bulkhead, then run another wire through a grommet to the ammeter.
View attachment 1715755116

Awesome, thanks for the info and diagrams! That’s exactly what we were hoping to find when I posted this. I really appreciate the input from both of you, I’m sure we can get it set up now, we were just drawing a blank as to how to make everything work and be NHRA legal.

 

[my68barracuda]

Or same concept as above with both wires through a grommet like a 'fleet' alternator wiring setup.
In this case the guy was planning on an engine compoartment and a trunk battery, but of course still needed to cut off power from the trunk.
View attachment 1715755118

Mattax, how is the relay interrupting one of the field wires better than simply using the small posts on the disconnect as the interruption point?

 

[Mattax]

Mattax, how is the relay interrupting one of the field wires better than simply using the small posts on the disconnect as the interruption point?

It saves a bunch of wire.
It's a long distance for the ignition run wire if it went to the trunk and back to the engine compartment. A larger diameter wire would be needed to be sure there was the same or less resistance than factory.

In theory you could run just a field wire to the kill switch. Resistance would still effect alternator performance but not voltage regulation. However given a choice, I would want a kill switch that disconnected the ignition along with the power sources.

 

[Mattax]

Awesome, thanks for the info and diagrams! That’s exactly what we were hoping to find when I posted this. I really appreciate the input from both of you, I’m sure we can get it set up now, we were just drawing a blank as to how to make everything work and be NHRA legal.

Great. When your sketching your diagrams keep in mind the ones I posted don't show the ignition-start wire, but the engine won't start without it. You can leave it on ballast resistor, or connect to the ignition run at the relay or at the ballast resistor terminal like was discussed above.


If it helps visualize things, here's how the terminal stud is set up on my car.
Heavy black wire is second output wire from the alternator. Black through the small grommet goes direct to the ammeter. Red is the MSD power source.

Hre's a pic of a piggy back terminal.

 

[my68barracuda]

It saves a bunch of wire.
It's a long distance for the ignition run wire if it went to the trunk and back to the engine compartment. A larger diameter wire would be needed to be sure there was the same or less resistance than factory.

In theory you could run just a field wire to the kill switch. Resistance would still effect alternator performance but not voltage regulation. However given a choice, I would want a kill switch that disconnected the ignition along with the power sources.

You are right about that, I had ran a relatively small wire maybe an 18 or 22 gauge back to the disconnect to break the field circuit. With the car running the volt meter needle was twitching so fast it was a blur. Swapped the light field wire out for something like a 10 gauge going to and from the rear disconnect and everything was fine.

 

[DusterJoe410.4]

There's a "several" ways to do this. So far as the MSD, you can hook the ballast wires together, then take the original coil+ wire and route that to the "small red" of the MSD which triggers the system "on." Main power "big red' goes to hot at all times

So far as the kill switch, I would add a relay to run the engine bay VR/ etc. This is to reduce voltage drop which causes overcharging, and will fit right in with your kill switch

Cut the blue "ign1" "run" wire coming out of the bulkhead. Use the firewall end to trigger a relay. Feed the relay contacts with a fuse/ breaker (say 20A) and mabye no14 or 12 off the starter relay stud. Now for the kill switch. Run two no1 4's up front from the disconnect. Connect them in series with the blue "run" wire triggering the relay coil. Ground other end of coil. Hook the engine bay end of the "run" wire to the NO contact

So pulling the disconnect will drop out the relay and kill both the ignition and the alternator. Nothing can "run on" with that setup

So in the end you cut the blue "run." wire. Firewall / bulkhead end connects to one wire from the small terminals on the disconnect. Other wire from disconnect connects to 86, which is the relay coil, and ground 85, other end of coil

Feed fuse/ breaker power from starter relay stud to 30

Connect the engine bay end of the blue "run" wire to 87

View attachment 1715755028

We are finally getting this set up and in, I’m confused as to what exactly we are doing at the disconnect. Is it one blue wire on each small lug of the disconnect one runs to 85 and the other to 86 on the relay?