[1968 GTO Resto-Mod]

i'm trying to figure out how to set up the wiring for my 68 GTO.
here is a photo of what the project looks like:



i have made several modifications already which may affect changes to the stock wiring system including upgrading to 100 amp 12SI alternator, converting automatic transmission to muncie 4 speed manual, and ron davis aluminum dual electric fan radiator.
the radiator comes with dedicated wiring harnesses and relays for each fan which wire directly into the fuse panel. also, i ordered the master grounding kit from ron davis as well.
i'm sticking with the mechanical water pump and mechanical fuel pump.

there are many aftermarket wiring harness options, many of which offer upgrades and flexibility for custom builds, but i have a difficult time knowing exactly what would work best for my application.

can anyone here help me understand what else i need to know before deciding how to proceed with the wiring for this project?
what should i be thinking about that i haven't yet taken into consideration?
what pitfalls are to be avoided?
does anyone with a 68 resto-mod project have a particular product or system that worked well for them that they might be willing to recommend?
i've never done a project like this before so i am very open to guidance and advice.
thanks in advance for your help!
danny

[HWYSTR455]

Yeah, I will be at this point fairly soon, mine goes to the body shop I believe today. Prior, when the car was running in it's previous condition, I had made a number of mods to the harness/wiring to support accessories like dual fans, electric pump, stereo/amps, etc. So I can give you some info on how I did it, how I plan to do it this time, so you need to determine which way you want to go.

One thing is, not sure a 100a alt will be enough. With fans, at idle, and an electric pump, with headlights on, the system will be almost maxed out, if not over taxed. So I suggest a 140a at min, unless you have a serpentine belt setup, then go to like a 200a. Reason being, alts usually are well below their' rated output at idle, and you need all you can get.

Max v-belts can handle are about 140a before the belt is overcome, so if you're v-belt, makes no sense going over 140a.

When you order an engine harness, have the alt power wire upgraded, or run another or different wire than what's in the harness. At min, 10/12G should be used, 8G is probably best.

Review the powerup!, remote sensing, and headlight mods at MAD Electric:

http://www.madelectrical.com/electrical-tech.shtml

One thing I did on the clone is I didn't make a proper common power point/buss bar, so when under full load, I do get a drop, and have to fix it. Bummer, because that harness I made I wrapped and it looks all nice now. Live and learn. Use one common power point for all power, have a wire go directly to it from the alt and the batt to it, and don't use the batt for that common point. Look at my photo album under my profile for a pic where I used a ford solenoid for the common point. Think I posted a couple threads here too. This also allows you to use only one cable to the starter, that is only live when cranking.

Do the headlight fix, it's important so other options/accessories in the interior get full power, and the headlight switch isn't loaded. Don't use regular radio shack relays or relay holders, they won't cut it. You can look at my clone build and take notes from when I did the powerup! mod, upgraded to H4 lamps, added relays, and used hi/lo for both (all 4) bulbs. (all 4 elements go on for hi beams).

Fans can draw more than 40a, so use properly rated connectors and wire. I used Deutsch connectors here, which work best.

This time around on the LeMans, I will wrap all the harnesses with nylon mesh/braided loom, it looks real nice, and manages the harness well. Multiple suppliers carry it.

I think this time I will use a auto wire aftermarket harness, mainly since it uses a fuse box that has ATO fuses. It's a lot of work putting one of those in, but it's less work than modifying the original.

On the LeMans, I ran one 2G wire from the supply block from the engine bay through the firewall to a stud under the dash, then back to the trunk to another stud, which I used to power stuff under the dash and in the trunk. I had a fuse block and relay block come off of both studs, and ran high amp stuff off those (like the fuel pump, bottle heater, etc). You can see one of them on my profile page photo album pics (trunk) for ideas.

Use quality TXL or GXL wire, and do yourself a favor and buy quality crimpers and connectors (not auto parts store garbage). You can find used crimpers on eBay if you want to save a little, but for the most part, you should really have a set already. The ratcheting crimpers are good for some stuff, but the plier type will most likely be your go-to.

I 'mentally' section the car off in to areas, like engine bay, pass compartment, and trunk, and address each area separately. In the engine compartment, there's 2 considerations, engine and accessory. Engine takes priority. Think out each area and have a plan of attack before you start, and leave room to easily add to accommodate future needs.

There's my morning bran-dump on the subject, hope you find some useful!

.

[1968 GTO Resto-Mod]

thanks for the info!
that's quite a bit of food for thought there...

just to clarify a few things:
i do not have electric fuel pump or water pump...
i have installed mechanical fuel pump and mechanical water pump.
i am planning to run a serpentine accessory drive with the 100 amp alternator.
tech support at ron davis told me that the 100 amp alternator would probably work fine as long as i wasn't running many other high powered accessories.
i have also been looking at the american autowire classic update harness kit.
this product offers many important upgrades and seems like it will also be adaptable to other changes i might make.
does anyone out there have any experience with the american autowire classic update harness kit for 1968 application?
thanks again!
danny

[68azbird]

I have installed the American auto wire kits in other GM vehicles. It's pretty straight forward and really nice to have a modern fuse panel and a bunch more circuits and the directions should make it easy for anyone to install.
I went the extra mile and soldered all the connections, even at all the crimp on light socket terminals.
You should figure a few days of work if you are into doing a really clean job. But it's well worth it.

[HWYSTR455]

All I'm suggesting is do your homework. First, none of the aftermarket wire harnesses use relays for the headlights, and even with halogens, you need relays. None of the aftermarket harnesses bypass the OE type headlight switch, so full load has to go to the switch. If you upgrade your bulbs, there will be a drop in voltage to the headlights.

http://www.americanautowire.com/view...-out-come-bac/

Most aftermarket wiring places offer add-on kits for certain situations, like the headlight relay kit, and if you were to get them all, you would be paying through the nose for all the 'stuff'. Find a good source for individual components, like Del-City or Waytek, and avoid the markup.

No aftermarket harness uses a remote voltage sensing/common power post, so any time a high load accessory is turned on, you will see a drop of voltage to the load. Most of the time you see it in the headlights, but fans and other accessories will see it too. Good example is MSD boxes, they flat require X volts, and it will die if it doesn't get it.

A 100a alt puts out maybe 40a at idle, unless it's a custom unit. You have to consider duty cycle too, so, if you have a full load amp rating of 100a, and your car uses all 100a of that, the alt won't last long. Headlights draw about 5a per bulb, x4 = 20a, add fans at idle and you're most likely at 40a already, if not more, so if it has a rating of 40a at idle, it will be at 100% duty cycle. If it works.

Not sure I would trust Ron Davis' shop and if it would 'probably' work, they're a radiator shop. Now Ron Francis is a different story, some top notch stuff there:

http://www.ronfrancis.com/

If you're ok with 'good enough', then just use the OE harness, there's no reason to go to an aftermarket one. Things change over time, and you add or remove stuff from your hobby car, so keep in mind even if you don't have it now, you may in the future. It's better to be prepared for it than chop and hack when you do. Ever plan on doing EFI? What happens when you start having a vapor lock issue? Or a fuel delivery issue? Or you notice when you're in heavy traffic on a hot day with A/C on it overheats? Adding an amp with a sub? Converting to power windows? All perfect examples of what I'm talking about.

Maybe go over to pro-touring.com, and post there, you will get a lot more ideas/suggestions, and from folks who do this for a living. Look at some of the project cars from DSE, see what they are doing for wiring. Gotta do your homework before you pull the trigger, just makes sense.

.

[1968 GTO Resto-Mod]

Originally Posted by 68azbird

I have installed the American auto wire kits in other GM vehicles...

Originally Posted by HWYSTR455

All I'm suggesting is do your homework...
...Gotta do your homework before you pull the trigger, just makes sense.
.

thank you so much for your input!
i really appreciate the advice.
also, thanks for including the web links.
i'm beginning to see that upgrading to a higher amp alternator might be a wise move in the long run.
in any case, i clearly have a lot of research to do... and a lot to learn.
cheers!
danny