Help in removing MSD 6A box
Thread Starter
Racer
Joined: Jan 2010
Posts: 402
Likes: 1
From: Medford NJ
Help in removing MSD 6A box
My '72 LT-1 came with an MSD 6A (not 6AL) box connected to my factory coil. I want to go completely stock and remove the MSD box, since I show the car and will go for NCRS judging in the future. I don't have a wiring diagram of the MSD box. Does anyone know the wiring that should be disconnected? Will I then need to change my plugs from the AC R44TS to a hotter plug?
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Everything you need is right here.
http://www.msdignition.com/uploadedF...structions.pdf
Job one is to remove the power leads, then trace the other wires and remove. a little masking tape to label stuff as you remove it will help a bunch. Unless yours is connected differently, the connection to the RED wire should go to the positive side of the coil, connection to the WHITE wire should go to the negative side of the coil.
http://www.msdignition.com/uploadedF...structions.pdf
Job one is to remove the power leads, then trace the other wires and remove. a little masking tape to label stuff as you remove it will help a bunch. Unless yours is connected differently, the connection to the RED wire should go to the positive side of the coil, connection to the WHITE wire should go to the negative side of the coil.
Last edited by billla; Sep 8, 2010 at 09:38 PM.
Thread Starter
Racer
Joined: Jan 2010
Posts: 402
Likes: 1
From: Medford NJ
Thats great. I just read through it. Thanks very much.
I was surprised to see that a plug gap of .050-.060 is recommended for engines under 10.5 to 1 compression! I've been setting the plugs at .035.
I was surprised to see that a plug gap of .050-.060 is recommended for engines under 10.5 to 1 compression! I've been setting the plugs at .035.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
If you are disconnecting the MSD box you will want to go back to the .035 gap. I have always run about .040 with the MSD setups with no problems. If you need help with the wiring I have all the 72 diagrams you need. I can make some copies for you and give them to you. I'm around for the next 2 days so let me know what you need.
You will want to remove all the MSD wiring and hopefully the stock wiring is still there. If not I can help you out.
You will want to remove all the MSD wiring and hopefully the stock wiring is still there. If not I can help you out.
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
There is no trick to yanking the MSD out: Just pull the box and disconnect all wires that come out of the MSD box: There will be a large red and large black connected to the battery, a smaller red connected to an "IGN" power source, a white wire connected to the distributor, and orange & black connected to the coil - just yank them all off. The trick is often to find and restore the original wires: They will often be cut. If they are not cut, simply connect the distributor wire to the "-" side of the coil and hook up the two coil power wires to the "+" side of the coil. Done.
Lars
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Tech Contributor
Joined: Aug 1999
Posts: 14,380
Likes: 6,391
From: At my Bar drinking and wrenching in Lafayette Colorado
Ahh - got it. That makes more sense and is correct, assuming that the previous installer wired the MSD incorrectly by using the resistor wire to the coil to power the MSD "red" lead, which is frequently done.
Lars
Lars
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Thread Starter
Racer
Joined: Jan 2010
Posts: 402
Likes: 1
From: Medford NJ
I pulled the wires from the MSD 6A box off of the coil terminals. It figures that the red wasn't connected to a direct 12v connection. Instead it was connected to the pos side of the coil. My original wires were still there, and in fact connected as well. You can see on the neg terminal that a non conductive spacer was installed on that post, so that the MSD white wire and the black distributor wire were connected (as per instructions). It was just an odd way to do it I guess. So it was an easy fix.
The black and white (insulated) wires are now connected to the pos terminal, and the black distributor wire is connected to the neg terminal. It starts up and runs fine.
The way this MSD was wired, was it getting a full 12 volts at the coil?
The black and white (insulated) wires are now connected to the pos terminal, and the black distributor wire is connected to the neg terminal. It starts up and runs fine.
The way this MSD was wired, was it getting a full 12 volts at the coil?
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Nice work sorting that out!
I might be thinking about it wrong, but I can't see the MSD getting a full 12V in that configuration...
BTW, a belated "nice ride" on your LT-1 - always my favorite ride!
I might be thinking about it wrong, but I can't see the MSD getting a full 12V in that configuration...
BTW, a belated "nice ride" on your LT-1 - always my favorite ride!
