MSD 6AL wiring question

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RON REAGLE

RON REAGLE

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Just installed all new wiring harnesses in my 68 340 Barracuda. The MSD 6AL wiring instructions show connecting the heavy red and heavy black (ground) wires to the battery. Trying to keep the installation "clean" and looking neat. Can I use the post on the starter relay for the 12v red wire or is it best to connect it to the battery post? As for the ground I have a ground strap on the rear passenger side head to the firewall. Is this sufficient to ground the black wire to?
 
I found that I had to go directly to the battery, otherwise the slight voltage drop caused the MSD to misfire.
 
If you can make it to the relay then the Battery should be no problem. I agree the relay could pull down some voltage during cranking.
 
i have used the starter relay post several times and not had a problem, engine block for ground is ok also. make sure you have several grounds from motor to chassis an battery.
 
Anywhere up to and including the battery terminal itself is gonna see a dip on cranking. That Starter relay input post is fine as its just a smaller gauge (but not smaller than the MSD's power) bridge tap off the + battery lug. MSD is supposed to fire down to 10V but at a reduced output.
 
RON REAGLE said:
Just installed all new wiring harnesses in my 68 340 Barracuda. The MSD 6AL wiring instructions show connecting the heavy red and heavy black (ground) wires to the battery. Trying to keep the installation "clean" and looking neat. Can I use the post on the starter relay for the 12v red wire or is it best to connect it to the battery post? As for the ground I have a ground strap on the rear passenger side head to the firewall. Is this sufficient to ground the black wire to?
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This is exactly why people have problems with these ignition boxes. Same thing happens with most aftermarket ECUs for fuel injection. Do it right, go to the battery. If you don’t, don’t go on some forum saying the MSD is junk when yours doesn’t work correctly. Something like 90% of failures are caused by bad installation practices.
 
The starter relay post will be fine if it is wired with large enough wire from the battery. Ron, what is the routing from battery to relay and what size wire did they use?
 
I bought very expensive "stock" cables which don't have any extra wires to add anything to. I am particular and don't want a cobbled up mess BUT I also want the wiring to work and perform PERFECTLY. Adding lugs to the battery terminals seems to be the best option. As always I appreciate the advice. Thanks
 
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