Notes on Hot Rod Wiring from Al at

Just a few things to consider when wiring your Hot Rod, Custom, Street Rod, Race Car or Boat.

If you are putting your battery in the trunk, running a Huge Stereo or have an alternator putting out over 100 amps use at least a number 8 AWG wire between the Alternator and the Battery.

If you want Brighter Headlights wire them up with a Relay so they get a full 12 - 14 volts from the battery.  See this example.

If you are using small taillights, such as '39 Fords or Early Chevy, use "Bright Bulbs" or Halogen Bulbs.  They DO make a Big Difference. 
Loose the Blue Dots... They may look Cool, but, they're Dangerous... Blue dots are outlawed in many states for a reason.  They block the light bulb right at the center of the taillight where most of the light would be emitted if they were not there.  At today’s speeds these early lights are not large enough to begin with....
I'll get off my soap box.

Be careful with the halogen bulbs they draw much more current, get hot enough to melt plastic housings and lenses and can melt wiring insulation if the wire is sized too small.  Make sure the wiring is up to the task before installing halogen bulbs.

Don't run a fuse larger than the amperage that the smallest wire in the circuit can safely carry.  Check this chart.   Remember the farther you go the heavier the wire needs to be.

If you are mounting the Battery in the Trunk, use at least a 1/0 battery cable (or better yet a Welding Cable).  Welding cables are built with a greater number of smaller wires to better carry the load and they are more flexible making routing the cable easier.  Be sure to properly secure and protect the cables against abrasion.  A battery disconnect switch at or near the battery to disconnect is an absolute must... Shorted Battery Cables Create Nasty Fires and can cause batteries to explode.  Make sure the battery is securely mounted in a battery box for this very reason.  

Steel is a poor electrical conductor. The large size of most automobile frames makes it possible to use them for a large bus bar in spite of this fact. Weld ground Studs to the frame, clean off all paint and use internal/external star washers on ALL battery cable connections.  Using dielectric grease at the connections will help to reduce corrosion.  Make sure the motor and the body are both properly grounded.  If it's a unibody car it's best to run a ground cable back up to the starter or engine block.

Most Automotive Electrical Problems are GROUNDING Problems.  If you're having a problem with something and find there is power to it double-check your grounds (including the battery cables).

Any and all comments are welcome.  If you feel something should be added please let me know.