I am getting ready to re-wire my 51' Dodge Wayfarer with a Flathead 6, with a Painless Wiring kit, do a 12 V conversion, HEI ignition, and 1 wire alternator. Any suggestions before I jump in? Kinda nervous, never done anything like it.....thanks in advance <!-- / message -->
My wife wired a 40 sedan with a Painless harness a few years back - really! And it only required one call to the tech guys 'cause she doesn't know **** about cars. You need to decide if you want to run each wire individually or use a pre-wired fuse block. I like pre-wired fuse block because it ***ures good connections at the block, but it can be tricky dealing with 12-18 circuits worth of wire all at once. And get a name brand harness with high temp (thinner) insulation, like Painless'. It'll make pulling the wires much easier. It's a simple job but not an easy job - if you know what I mean.
Lay the harness out on the floor. Decide where you will route circuits front to back, left to right and which circuits go that way, then bundle those to form the harness to route that way. Painless does not supply the ground circuits so you need to include having extra wire for grounding. A good set of wire strippers and crimpers is a must. There directions are pretty good when you look at the list of where each wire starts to where it ends. Every wire has the circuit number and function and wire gauge on it every few inches. Circuits for the heater and wiper are power only so you will need a schematic of what your car has right now and make a new harness for those. Good luck,once you get going it is not that bad.
Its a little daunting at first. Take it slow, and start with the simple stuff like the lights first. then by the time you get into the dash and engine it'll make more sense. Worked for me.
I worked with one several years ago - we didn't have a "normal" installation due to the ignition type we had - the lack of them supplying a schematic made the installation PAINFUL. I could see it being OK for a "normal" install, but their instructions were unnecessarily complicated - a picture is worth a thousand words or in this case a schematic would have been worth a thousand words. After that experience I wouldn't use anyone's kit UNLESS they gave a schematic with it, but that's just me.
As 4tford noted get yourself a good set of wire strippers and crimpers. Insulated terminals and noninsulated typically require different types of crimpers. After you decide which type you want to use, get yourself a pair of Klien or Ideal crimpers (forget those el cheapos). I've seen a lot of fuse boxes buried behind the dash...give some thought to your installed location thinking about changing a fuse on the side of the road, during the dark on a raining night.
In a previous post, one of the guys mentioned that the first thing he did was cut all the bundle ties that the manufacturer puts on. About 70% through my '31A, I realized that I had done just that, one at a time, lying on my back, with something sharp poking me somewhere. Seriously, take your time, think about what you want it to look like re: fuse block location wire routing, firewall penetrations, etc., and go slow. They typically give you way more wire than you need (Painless, anyway), so pull them to the general vicinity of where you're going to land them and coil and tape them until you're ready to land wires. Painless talks about using a battery charger as a checkout power source, but I just put an in-line fuse holder in the battery circuit and used 10's and 20's amp fuses. Just don't hit the starter while you're working with the tiny fuses in the circuit. It works very well until you drop a hot wire on a steel floor pan, and then you have to do the fuse change thing; buy a few spares Take your time, and don't let it psyche you out. It's plumbing for sparkies, that's all.
I have used 4 brands of harnesses, they all pretty much get the job done. Use the above recommendations and it will be a breeze.
I used "Itsasnap" 20 circuit system very similar to Painless. First time I've ever tried wiring. I laid everything out on the floor and went through doing all the various bundles. Had an octopus laying on the floor at the end. Then routed everything through the firewall, floor etc. Wound up unbundling everything and rerouting half the wires. Third time around I only had to reroute about half of those. The worst part for me was the size of the bundles where they enter into the fuse block. They wouldn't bend as easily as I needed to make some fairly sharp bends. It took a while and there were a couple of times I was very frustrated but I'm pleased with the result and I'll certainly do it again myself. All the tips above are good ones.
Lay it out first as said, figure where everything goes. The brake wires for brake lites are usually in the wrong spot if you are using an under the floor, the only hard parts are some of the wording (left turn is stop lite filament) **** like that, and the only difficult wire areas are headlite switch, turns and maybe one or so more circuts varying by car. All in all Id take wiring over welding any day of the week haha.
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