Prepping the Driveline
Like most other forms of motorsports, this is where the races are often won or lost.
First order of business: rip out all the original wiring. When your car's body starts getting banged up in the derby, some important wire is bound to get pinched somewhere, short out, and kill the car. End of race. On most cars you only need to run one wire to the starter, one to the coil, and a couple to the alternator. And maybe one to the stereo too, if you like to blast out Ride of the Valkyries as you make your entrance.
If your car has an automatic choke, disable it. When your car gets hit, the g forces will cause an automatic choke to slam shut, flood the engine, and stall. Then you have to crank and crank and crank to get it going again. I like to install a manual choke, but you can just wire the choke to the full open position if you'd prefer. The car will run rough for a couple of minutes while it warms up, but by the time the derby starts, it should be okay.
If your car has an automatic transmission, remove the entire shifter linkage. After a few hits the linkage will fly apart, leaving you without the ability to choose gears. It's a simple task to cut a hole in the floor just to the right of the gas pedal and bolt a 1/2 inch pipe onto the transmission selector. You'll have enough travel in the pipe to get Drive (pipe forward, hitting the dash), Neutral (pipe middle) and Reverse (pipe hitting the seat).
Automatic transmissions cool their oil by using a tank inside the radiator. The steel lines used to get the fluid to the radiator are easily kinked or split, so you'll want to replace a 2 foot section of each steel line with some kind of flexible hose to allow for movement of the radiator. Note that this fluid is under fairly high pressure (upwards of 300 psi) so you can't use plain rubber hose or else it will burst. I've always used neoprene gas line without any problems. An even better solution is to make your own cooler. You can use an old heater core, solder in some connectors, attach a fan, and place it behind your seat where it's safe.
Some people will tell you that a radiator isn't necessary in a derby, but I disagree. Even though Chevys are renowned for their ability to run hot, why tempt fate? If you do remove the radiator, be sure to keep the heater core and run a live wire to the heater fan. You'd be surprised how much engine heat one of those suckers can dissipate. Should you decide to keep the radiator, never use a solid fan; if the radiator gets shoved back into the fan, it will snuff the engine. There's really no need to use a radiator fan in the derby anyway, since the sheer volume of water in the cooling system will absorb enough heat to run your car for 20 minutes or more.
Be sure to replace the factory fasteners on the radiator with baling wire or cable ties to hold it in place. This gives the radiator the freedom to move around a little bit and not break.
Two more cooling tips: 1) use a 50/50 mix of antifreeze instead of straight water, since it boils at a higher temperature than plain water, and 2) turn the radiator cap back to its first position so that the cooling system isn't running under pressure, and is thus less likely to blow a hose.
You may have heard someone tell you to run oil in your cooling system since it won't boil. It won't work.
If using a small block Chevy or Chrysler, the distributor is located at the very back of the motor right next to the firewall. A couple of good hits in the derby and the engine will shove back far enough for the distributor to hit the firewall and break or get knocked off. Give yourself enough clearance by cutting out a generous window behind the distributor with a torch or chisel.
As mentioned earlier, power is not a big deal. Thus, it won't hurt to retard the spark timing a little bit by turning the distributor clockwise, maybe by about 10 degrees. This has two benefits: the engine will run a smidgeon cooler, and it will be a lot easier to start when hot.
To protect the distributor and wires from getting wet and stalling the engine, I coat everything in sight with a product called "Ignition Protector" (available at your local auto parts store). It comes in an aerosol can and dries to form a protective layer after a few minutes. Apply three to four very liberal coats.
Some people doubt whether or not an alternator provides much benefit during a derby, but to me there's no question. You'll have to start your car many times during the course of a derby, often with the engine really hot and/or flooded, and this takes a lot of power. Trust me, you'll be thankful for all the amps you can get your hands on. Plus, there are other reasons to leave the alternator hooked up:
- When an alternator is charging, the electrical system runs 1.5 to 2.0 volts higher than with just a battery. This extra juice is amplified by the ignition system, which in turn provides a stronger, hotter spark and is thus better able to fire you spark plugs under the less-than-ideal conditions encountered in a derby
- I install a voltmeter to tell me if the engine's running (you can't hear your own motor in the middle of a derby). This could also be accomplished with an oil pressure gauge/light, but the voltmeter will also tell me if my starter is cranking, so I only need one gauge.
- The alternator belt often runs the water pump.
- It's already there, so I just have to run a couple of wires to it.
- Like money, you can never have too much battery power in reserve.
For instructions on wiring an old-school Delco (GM) alternator, click here.
This is one area in which you don't want to skimp. Get the biggest battery the rules will allow and make sure it can hold a charge. There are few things more frustrating than losing because you didn't have enough battery to start a hot engine.
Most derbies make you relocate the battery from under the hood to the front passenger floor. I'm not entirely convinced that moving 50 pounds of explosive sulfuric acid closer to the driver is a safety advantage, but I don't make the rules. Be sure to bolt it down very securely and cover it with a thick rubber material such as a mud flap or tractor tire inner tube.
If you're having trouble with a battery that drains itself overnight (and you still have the original wiring), try this troubleshooting tip.
If you have rear leaf springs, you're in pretty good shape. Some people will arch them up a little bit gain some height out back, both for added clearance and to get into the optimal striking range. I like my rear bumper to line up with the top of the rear tires (about 22-24" off the ground) so that if they hit an opponent's tires, they'll do the most damage. At that height there's a decent chance of breaking the guy's axle/spindle/bearings.
If your car has coils out back (as most newer cars do), you have to guard against them popping out if you get hit hard in the back, since most cars just have the coils sitting loosely in a pocket. Buy or make some strong clamps and anchor both ends of the spring solidly to its pocket.
Most people recommend welding the spider gears in a differential so that both wheels are locked together. (In a typical "open" differential each wheel receives the same amount of torque, causing the wheel with the least amount of traction to spin.) I've never done this, mainly because I don't have the talent or patience to do it right. But for some reason, cars that have their spiders welded tend to exhibit an awful lot of axle tramp when the power is applied. Sometimes these cars will even get stuck all by themselves, which is what this procedure is supposed to prevent. On balance, however, welding is probably still better than not welding, but I wouldn't sweat it either way.
Next: Preparing the Body