I have a small switch that is rated at 3A at 125vac, 1A at 250vac. I want to use it as a kill switch. My plan is to put it/hide it on the negative line going to the distributor. When switched off ,the negative line to the distrbutor would be broken. Could there be any problems with this application?

DC Rule of Thumb
For those switches that list an AC voltage rating only, the "DC Rule of Thumb" can be applied for determining the switch's maximum DC current rating. This "rule" states the highest amperage on the switch should perform satisfactorily up to 30 volts DC. For example, a switch which is rated at 10A 250VAC; 15A 125VAC; 3/4HP 125-250VAC, will be likely to perform satisfactorily at 15 amps up to 30 volts DC (VDC).

http://www.carlingtech.com/products/switches/learn_more.asp?page=switches_amp-rating

Switching DC is a little different than switching AC. If you are going to ground out the points, you may be handling more than 8 amps or so, depending on whether or not the points are closed and the ballast resistor is in the circuit. Actuating the switch while the engine is running may result in severely shortened life due to the arcing. I would look for a larger switch.

Don't ask me how to wire it up, but you could use a relay to handle the load, and the small switch to handle the relay. Hide the relay and use the small switch where you need it.

Thank You,the website is great and I have emailed them. I hope that I never hit this switch while the car is running,do you see any other drawbacks?

IF you have a points type distributor, just connect one side of the switch to ground and the other side of the switch to the neg. side of the coil rather than cut that wire.
Turning ON the switch will ground out the points and disable the points/coil.

Tanks Dean,just like the cigarette llighter trick,but if I went that route would the small switch handle that load? Is there amps going thru the line if I am just grounding it out? I don't know much about electronics,and I want to be certain.

The smallest switch you can buy will work fine.

Dean,Thank You for sharing your knowledge.