Wiring question for those with an MSD ignition box
11-06-2016, 10:09 PM
#1
Burning Brakes
Thread Starter
Wiring question for those with an MSD ignition box
Recently purchased a MSD 6AL-2 ignition box for my 71. Got the box mounted and the heavy gauge positive and negative wires hooked up.
However, trying to find a good connection point for the smaller red ignition wire that requires 12v with key on and while cranking. I checked the "IGN" spade at the fuse box during cranking and it appears that the 12v with key on/ignition on drops to 0v during cranking.
For those of you that have an MSD box installed, where did you connect this wire? Is there another wire somewhere that I can tap into that has 12v with key on as well as during cranking? Thinking maybe one of the wires at the ignition switch might work, but not sure...
Any guidance would be appreciated. Thanks!
However, trying to find a good connection point for the smaller red ignition wire that requires 12v with key on and while cranking. I checked the "IGN" spade at the fuse box during cranking and it appears that the 12v with key on/ignition on drops to 0v during cranking.
For those of you that have an MSD box installed, where did you connect this wire? Is there another wire somewhere that I can tap into that has 12v with key on as well as during cranking? Thinking maybe one of the wires at the ignition switch might work, but not sure...
Any guidance would be appreciated. Thanks!
11-07-2016, 04:50 AM
#2
Team Owner
I have a 6AL box but it's been awhile since I wired it. I'll look at it when I get home (I work nights) and see how I did it. I can't remember off the top of my head but I think I used the original resistor wire. I am running an MSD distributor too.
Forgot......mine's a '71 also
Forgot......mine's a '71 also
Last edited by theandies; 11-07-2016 at 04:51 AM.
11-08-2016, 07:44 PM
#5
Race Director
Sounds like a good wire to use but I would call MSD and make sure that the resistance wire is acceptable ...so the unit is getting the correct 12 volts it really needs to be at its best performance.
The reason I 'question' stuff like this...is I get a lot of Corvettes that drive into my shop and run. Some have had their points distributor removed and an HEI installed.,...and they still use the resistance wire or a smaller gauge wire that connects to the HEI than what GM designed to feed power to the HEI. Because if you have a wiring diagram...you will see the wire coming off your ignition switch is a pink 12 gauge wire...and when it connects to the bulk head connector...it changes to the resistance wire. And if you look at a later design Corvette with an HEI...the wire does not change gauge size....it stays the same and a 12 gauge wire.
And...not knowing IF the MSD is that critical (which is why I suggest you call them)...is because when I do upgrades like this. I remove the bulk head connector and remove the resistance wire from it. And then I install a wire that is not a resistance wire. I do it this way because I cannot take the chance of not giving the MSD the best possible chance of success....and seeing how I have dealt with the bulk head connectors and have the terminals and crimping tools to do this...it is not like pulling teeth for me to do this.
DUB
The reason I 'question' stuff like this...is I get a lot of Corvettes that drive into my shop and run. Some have had their points distributor removed and an HEI installed.,...and they still use the resistance wire or a smaller gauge wire that connects to the HEI than what GM designed to feed power to the HEI. Because if you have a wiring diagram...you will see the wire coming off your ignition switch is a pink 12 gauge wire...and when it connects to the bulk head connector...it changes to the resistance wire. And if you look at a later design Corvette with an HEI...the wire does not change gauge size....it stays the same and a 12 gauge wire.
And...not knowing IF the MSD is that critical (which is why I suggest you call them)...is because when I do upgrades like this. I remove the bulk head connector and remove the resistance wire from it. And then I install a wire that is not a resistance wire. I do it this way because I cannot take the chance of not giving the MSD the best possible chance of success....and seeing how I have dealt with the bulk head connectors and have the terminals and crimping tools to do this...it is not like pulling teeth for me to do this.
DUB
11-08-2016, 09:32 PM
#6
Team Owner
Sounds like a good wire to use but I would call MSD and make sure that the resistance wire is acceptable ...so the unit is getting the correct 12 volts it really needs to be at its best performance.
The reason I 'question' stuff like this...is I get a lot of Corvettes that drive into my shop and run. Some have had their points distributor removed and an HEI installed.,...and they still use the resistance wire or a smaller gauge wire that connects to the HEI than what GM designed to feed power to the HEI. Because if you have a wiring diagram...you will see the wire coming off your ignition switch is a pink 12 gauge wire...and when it connects to the bulk head connector...it changes to the resistance wire. And if you look at a later design Corvette with an HEI...the wire does not change gauge size....it stays the same and a 12 gauge wire.
And...not knowing IF the MSD is that critical (which is why I suggest you call them)...is because when I do upgrades like this. I remove the bulk head connector and remove the resistance wire from it. And then I install a wire that is not a resistance wire. I do it this way because I cannot take the chance of not giving the MSD the best possible chance of success....and seeing how I have dealt with the bulk head connectors and have the terminals and crimping tools to do this...it is not like pulling teeth for me to do this.
DUB
The reason I 'question' stuff like this...is I get a lot of Corvettes that drive into my shop and run. Some have had their points distributor removed and an HEI installed.,...and they still use the resistance wire or a smaller gauge wire that connects to the HEI than what GM designed to feed power to the HEI. Because if you have a wiring diagram...you will see the wire coming off your ignition switch is a pink 12 gauge wire...and when it connects to the bulk head connector...it changes to the resistance wire. And if you look at a later design Corvette with an HEI...the wire does not change gauge size....it stays the same and a 12 gauge wire.
And...not knowing IF the MSD is that critical (which is why I suggest you call them)...is because when I do upgrades like this. I remove the bulk head connector and remove the resistance wire from it. And then I install a wire that is not a resistance wire. I do it this way because I cannot take the chance of not giving the MSD the best possible chance of success....and seeing how I have dealt with the bulk head connectors and have the terminals and crimping tools to do this...it is not like pulling teeth for me to do this.
DUB
11-08-2016, 10:58 PM
#7
Race Director
The ignition coil is fed 12v from the starter when cranking and approximately 8v when running . The starter has 2 small terminals. One is the trip = key and the other is the coil feed while cranking.
I connected the coil wires to a relay which closes with both the 12v from the starter and the 8v from the resistance wire. I then took a 12 v feed from the horn relay to the new relay and then to the box. This gives the box a true 12 volts as they require.
I connected the coil wires to a relay which closes with both the 12v from the starter and the 8v from the resistance wire. I then took a 12 v feed from the horn relay to the new relay and then to the box. This gives the box a true 12 volts as they require.
Last edited by BLUE1972; 11-08-2016 at 11:00 PM.
11-09-2016, 11:48 AM
#8
Melting Slicks
I use the resistance wire. To be safe get as close to the bulkhead connector and splice (crimp) to the stub after you cut off as much as possible. That will guarantee very little resistance.
The wire cannot be soldered to. So crimp or run inside to fusebox, yes there is the correct male pin there to attach to.
The wire cannot be soldered to. So crimp or run inside to fusebox, yes there is the correct male pin there to attach to.
Last edited by mikem350; 11-09-2016 at 02:13 PM.
11-09-2016, 12:49 PM
#9
Burning Brakes
You can use the resistor wire.
The voltage on the resistor wire only drops to 8-9 Volt when using the stock setup. This is because in the stock setup the coil pulls its current through the resistor wire.
The input on the MSD doesn't pull a high current (it has a high resistance) so the voltage at the end of the resistor wire will be full battery voltage.
/Karsten
The voltage on the resistor wire only drops to 8-9 Volt when using the stock setup. This is because in the stock setup the coil pulls its current through the resistor wire.
The input on the MSD doesn't pull a high current (it has a high resistance) so the voltage at the end of the resistor wire will be full battery voltage.
/Karsten
Last edited by Danish Shark; 11-09-2016 at 12:49 PM.
11-09-2016, 11:39 PM
#12
Burning Brakes
Thread Starter
Hi guys. Thanks for the great information! I've installed all new wire harnesses from Lectric Limited, but don't yet have the dash back together. Since the dash is still out, I will have easy access to the wiring, fuse block, ignition switch, etc. It sounds like some of you are using the resistance wire that goes to the coil with no issues. However, I have already routed the smaller ignition box red wire to the inside of the car, so I am wondering if I can simply just splice/solder the small red "ignition" wire from the ignition box to the pink wire at the ignition switch that DUB referenced or I could take it a step further like he does and completely remove the resistance wire from the fuse/junction block and install a "real" wire in its place and run it straight over to the ignition box. Although a little more time consuming, I wouldn't be opposed to going that route either. Well if any of you have additional input, I'm all ears. Thanks again for taking the time to respond...
11-10-2016, 06:23 AM
#13
Burning Brakes
In that case I would leave the resistor wire in place and wrap it to the harness with wiring harness tape. That way it's out of the way and you still have the option of going back to stock.
Last edited by Danish Shark; 11-10-2016 at 06:23 AM.