How to ground your magneto with a standard two post master switch.

[ricci32]

Is there an easy way to ground your mag with a standard two post cut off switch.

[Spud Miller]

 Hmm. Not sure what you mean exactly by a two post switch. Do you mean a regular make/break type of switch with two terminals?

 If so, then you'd just hook the + coil terminal to one post and the - terminal to the other. When they're connected, the mag is defeated/grounded. Of course, you'd need the negative terminal of the coil grounded to something good too.

 Lots of folks run the hot wire from the coil to the switch, but then just run the ground side of the switch to the chassis or something. The best ground is the other terminal of the coil. You have to run two wires to the coil instead of just one, but it really is the best way to go.

 If you're referring to a different type of switch, let me know and we'll figure it out!

 Spud

[ricci32]

Let me explain I have a master cut off switch I wish to install at the rear of my front engine dragster which uses a standard battery and starter and has a internal coil joe hunt mag when the switch is in the off position the circuit is open and I need to ground the magneto how do I achieve this using that two terminal cut off switch. I still have a on off toggle switch to ground mag on the dash .

[BK]

  Because a Mag makes its own power your only looking to ground it to the chassis to shut the engine down. Nothing from the main switch should go to ground. You might be able to do it with a relay.
  If your battery is up front you may want to consider moving your master switch up near the battery and controlling it from the back with a cable. That way you don't have a live cable going from front to back looking for a place to short out. It gives you a chance to put a lever in the cockpit to control the battery power. Also the control cable is probably lighter than your battery cable.

[George]

I use the Flaming River Combination Magneto & Battery Kill Switch. http://www.flamingriver.com/index.php/products/c0015/s0002/FR1010                                                                                                                           
It is mounted to the rear of the Powerglide dipstick area and is operated from the rear of the car. It is indexed to  "Push Off".   A SPST toggle switch is in the drivers compartment. Its main function is to light the engine off.

[Spud Miller]

 The bummer about the flaming River switch, is that you have to run your primary mag hot wire the length of the car. Not a very good deal. Over time, the chances of it getting rubbed raw and leaving your mag dead are too great in my opinion.

 Using a relay is what I suggest. When you cut the power to the car, the relay relaxes and grounds the mag.

 Just be sure to use one that is impervious to vibration and can handle the voltage and current. We offer this one:
 http://fuelinjectionent.com/webstore/product_info.php?products_id=350

 It's really two separate relays in one unit. You can double up and use both sides together to double it's capacity, leave the other side for a spare, or kill two mags with it.

 Spud

[George]

The Flaming River switch has worked well with the MSD 12lt setup.

[ricci32]

Thanks spud that is what I was looking for.

[32bantam]

If you use one of the "universal" type block relays...........
1. make sure it is a high amp model.....30/40 amp
2. wire tye it to the harness. Do not mount it to anything. That way it is free from vibration that being mounted brings.
Steve

[Spud Miller]

 Yup, good tips Steve.

 The higher the voltage rating the better too. Make sure it's rated for a high current at 240VAC at least.

 Spud

[H.G. Wells]

 The bummer about the flaming River switch, is that you have to run your primary mag hot wire the length of the car. Not a very good deal. Over time, the chances of it getting rubbed raw and leaving your mag dead are too great in my opinion.

 Using a relay is what I suggest. When you cut the power to the car, the relay relaxes and grounds the mag.

 Just be sure to use one that is impervious to vibration and can handle the voltage and current. We offer this one:
 http://fuelinjectionent.com/webstore/product_info.php?products_id=350

 It's really two separate relays in one unit. You can double up and use both sides together to double it's capacity, leave the other side for a spare, or kill two mags with it.

 Spud

I wish I had pics, but I mounted my flaming river relay under the cowl and the master disconnect where the stock fuel pump would have gone.  Ran a morse cable from the chute pack to the master.  Very little wiring that way.

[Geri]

let me add a little to this, I have two mag switches on my car-  (blown fuel) one for the driver and one mounted in front of the engine next to the fuel shutoff, in case I need to shut it down I can turn off the mag from either location.   as long as both switches are open, the magneto will run, with either mag switchs grounded it will shut off the engine. this for me is a safety issue. the switch only requires one wire to the mag the other to chassis ground. a normally on toggle switch  will kill the magneto as it completes the circuit to ground. that only means what appears to be off is actually run position for a toggle switch.
I have never bought the notion that shutting off an engine with the mag switch will blow up the engine or lift the blower- you cannot take the flame source away from the potential and cause a flame. others are free to believe what they may,I have used the mag switch to shut down the engine for as long as I  can remember (after first turning off the fuel)

[ricci32]

thanks im going to install a master cut off switch at the rear of the car I also use a marine push pull switch in the cockpit to ground the mag the relay that spud sells will allow me to kill the  fuelpump ,mag from the master at the rear of the car . this is on my nostalgia fed.