Originally Posted by 93 ragtop

For you and me, the fuel pump may work being injected. But the majority of cars are still carbed, at least in bracket racing in my area.
Ill promise you, NHRA has had lawyers and engineers look at this......

FWIW you could probably get away with the FP switch..... Most inspectors are going to test the switch and that is it.

Originally Posted by Hot Rod Roy

NHRA will do what NHRA wants to do, but why not just kill the ignition and eliminate all that dangerous cabling???

Originally Posted by 383vett

How is the alternator connected to the battery when the positive terminal is off the battery which essentially is what the master disconnect switch accomplishes?

Originally Posted by Krusty84

NHRA wants the engine shut off and no current going through the power distribution block to any accessory in the event of an accident. Considering it is practically impossible to disconnect the negative side of the alternator and battery at the same time, the only way cut off power to the distribution block is to disconnect the positive side of the alt and battery at the same time with a master disconnect. If I had to guess as to why the NHRA wants the disconnect on the (+) side.... It is to firstly shut off the vehicle, secondly to stop the flow of fuel and thirdly to reduce the possibility of a short at the front of the vehicle which is the most likely area of the car to sustain damage and leak fuel in a drag strip accident.

My setup for example will only have about 4-5 feet of 1/0 gauge wire running to the battery to the switch and about 12-15 feet of 2 gauge running from the alt to the switch. The 2 gauge from the alt will have a 250 amp inline fuse that will pop in the event of a short out so only 4-5 feet of the 1/0 will really be of concern and that isn't all that far off from the distances used if the battery was located at the front of the car. Another reason why the NHRA wants a master disconnect is because the track officials/workers/safety team have absolutely no idea where the relocated battery is located in the car. If there is no switch on the back of the car, they know where to look to disconnect power... Under the hood.

Originally Posted by ihatebarkingdogs

I think you're going to find that that the engine will stay running. Here's why: (I'm ASSuming that you have stock wiring and a stock alternator for a 1984 Corvette).

The turn-on wire for the alternator is the brn/wht wire in the 2-cavity plug. This wire originates at the IGN switch. It is HOT when the engine is running. In your proposed circuit, yes the power block and all power circuits will be isolated from the battery, but if the engine is running when you flip the switch, power generated by the alternator is back-fed through the brn/white wire to the IGN switch to the pink wire IGN circuits, and the engine stays running.

Do this little test on your car: With the engine running, remove the alternator plug. Does the alternator turn off? It should. Use a volt meter at the battery or output to confirm. If the alternator DOES turn off with the plug removed, proceed:

Here's a simple way to do it. I've used it, I've installed it. It works.

Wire the Large terminals on the battery switch between the Starter Solenoid Batt terminal and the Battery B+ terminal. (Obvious.) A fuse near the battery is good practice.
Cut the brn/wht alternator plug wire in two. Using #14 wire, connect the now (2) brn/wht wires to the small terminals on the battery switch.

When you turn off the battery switch, the little terminals open before the big terminals. So the alternator is turned off before its output is opened from the battery. With the alternator turned off, and the battery disconnected, the engine will stop running. Which is what the tech guy wants to see.

Originally Posted by ihatebarkingdogs

Was thoughtful of you to leave that little detail out of your initial post.

I spent about a half hour this morning verifying the circuitry in a 1984, and writing my response. I was attempting to clarify some of the mis information, and mis understandings other participants in this thread appear to have. If I'd know it was a swap, I wouldn't have bothered, because it was a waste of time as what I suggested doesn't apply.