Yeah I was going to go to the key on wire because I know it will stop charging as soon as that wire looses voltage. I just have to figure out where the switch is going to be in the circuit.
Gus

I used a 4 terminal switch and wired the MSD power wire to the switched side of the terminal. Kills the ignition immediately.

I was wondering if anyone ever wired one that way. What gauge wire did you use? 8-10

Thanks

Gus

That would probably pass tech almost anywhere but if I understand what you described correctly, what do you do about other critical components, like an electric fuel pump if you have one. If you need everything shut off in an emergency, especially if you can't, you might have a real bad situation on your hands.

I believe you are correct.. in the rule book it states it
should kill ALL power... but its been a while since I've
read that section

Engine shuts off alternator doesn't charge, fuel pump shuts off when when voltage is not present to energize the relay

Gus

I see what you're saying Gus and 70hemiGTX. You're right. My mistake. As long as the battery is by itself on one large terminal and everything else is on the other large terminal, it would do exactly that.

I too have wired the last few buddies cars this way (1st contact pos. battery, MSD small red wire on 2nd contacts of switch). This allows you to

A) Have short length altenator wire of smaller size (weight)

B)All battey power is off up front when the disconnect is off

C)You have no problems with engine run on after switch is thrown caused by altenator of any style

This is what the rule book states:

An electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the positive side of the electrical system and must stop all electrical functions including magneto ignition. The off position must be clearly indicated with the word “OFF.” If switch is “push/pull” type, “push” must be the action for shutting off the electrical system, “pull” to turn it on. Any rods or cables used to activate the switch must be minimum 1/8-inch diameter. Plastic or keyed switches prohibited. Switches and/or controls must be located behind rear wheels on rear-engine dragsters.

Contrary to what most people think, the main battery cable from e the starter to the battery does NOT need to be disconnected through the disconnect switch as long as all electrical functions shut off (engine, fuel pump, water pump, etc.). I verified this with NHRA tech some years ago. This is also how you get away with a lower rated switch.

There is a lot of ways to wire this, but if the switch doesn't cut alternator charge off, that wire can keep the system charged as the engine slows down. If you have ever seen a throttle stick and the battery switch is turned off, its a LONG time before that engine stops. This can be several seconds of a fuel pump running pumping fuel someplace you don't want it to go. Please consider this important safety factor.

My suggestion is leave the battery in the engine compartment, and save yourself a ton of time and money. I would like to see if any actual testing has been done to prove if any actual performance is gained with a battery in the trunk. I know the car will gain weight with all the extra heavy wire. Your wallet will be lighter with all the parts you need to buy to do it correctly and safely. I won't ever do it again, lot of work for very little if any gain in my opinion. The engine compartment looks nicer, thats about it. I have a excellent wiring diagram, but I can't post it here, since I have it saved to my computer, not on a website. I hate the way Moparts is now, can't save good forum threads (lost tons of great ones), and impossible to add photos now. I can email you a version if you want it.