Hidden Wiring


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Hi guys.

I have been asked to give a few pointers and pics on the "simplification" of my engine bay.


This project which I undertook was not so much one big upgrade but rather many little side jobs which worked together to ultimately give the engine bay the "neat and tidy" look.

Part of the simple look includes hiding as much wiring as possible.

The idea of hidden wiring became a very tempting choice for me once the engine was out and I was in the process of restoring the engine bay.

(I was devastated when my original block developed fatigue cracks and the engine had to be rebuilt but in another way, I was completely relieved that I can finally do the engine bay properly the way I envisioned it should look.)

At the time I modded the car, I was making it up "as I went along", but with hindsight I can document the order in which I performed the tasks. (All pictures taken after the fact for this tutorial).

As I had the luxury of a blank canvas to work on, I did more than just hide wires to make the engine bay look "clean".

(pictures with descriptions below)

With empty engine bay, I stripped the engine bay back to bare metal.

I did this because there was several uneven layers of paint and touchups and I also needed a good view of factory spot welds.

With the engine out, I also rectified various other little issues. Namely, the battery tray for the obvious reasons, the 2 front inner skins due to dents/rust, and I unstitched the radiator support to reweld it in its proper place. This is why my hood never lined up perfectly. Fixed some rust in the cowl also.

I then started by filling in any factory spot welds I can see.

(mig and flap). These were mainly on the shock towers and the procedure was for cosmetic reasons only.

I then decided to relocate the main bunch of engine bay wires which were entering the engine bay via the firewall and redirect them out the side behind the splash shield (for protection).

I found it easier to just make a hole in the corner of the engine bay (rear inner skin side) only inches away from the original hole in the firewall, and redirect all the wires there through it and just cover that corner of the engine bay with a discreet cover plate.

So at this stage, and with the drivers side splash shield off, you have all the wiring originally coming out of the firewall. I ended cutting them all and left about 6 inches behind the splash shield so I can solder new wiring to. It's not important to actually join the wires at this stage. I actually soldered them together when all wiring was in place from the firewall forward. I cannot emphasize enough the importance of careful labelling and documenting of all wires!

I then decided the easiest way to mount and secure the new hidden wiring was to weld some largish washers every 18 inches or so on the body accessible from under the fender and continue under the radiator and to the other side. Once welded, I bought matching grommets to suit. This will now be the new route for all the new wiring. The grommet holes need to be large enough to fit all the wires and would be wise to allow for 2 or 3 extra wires. Once all the wires have been threaded through, I began wiring up miscellanous components.

First I relocated both horns to the radiator support and wired them up.

Then I wired up the electronic fuel pump, windshield wiper motor, safety neutral switch, headlights, sports lamps, etc. It might be a good time to point out that I have employed many relays for various functions (eg: horns, h4 headlights, fuel pump, etc)

All these relays gangs are all taped up and tucked away behind the splash shield also where the new junction of wires now reside.

Ok, so the drivers side shock tower is now "wire free" so now we do the passenger side.

One eye sore for me has always been the starter relay, regulator and positive junction post and all the wires hanging off them. All these had to go! So the starter relay was relocated down the back where the charcoal cannister used to live. Here I made the high amp starter connection on the starter relay also the positive junction point, and the regulator and all its associated wiring was made obsolete buy purchasing a new one wire alternator (with integrated regulator).

As I still kept my battery in its original location I ran the heavy positive battery cable through the inner skin and under the guard like

the other side. This connected through the rear inner skin right where the starter relay now lives. From the positive junction point, a 6 gauge cable goes through to the passenger cabin behind the passenger splash shield and under the dash to my new fuse box. This is the main positive cable which all other fused circuits get their power from. (This replaces our yellow cable).

There are about 5 or 6 wires which are needed by the engine.

12v coil (new electronic dizzy)

oil temp sender wire

engine temp sender wire

holley choke wire (12V) if needed

tacho wire from dizzy

alternator idiot light


This little bunch of wires are directed from their new home behind the drivers side splash shield but do not go via the washers and grommets under the fenders. They instead follow a path along the firewall to a plastic junction box in the upper center of the firewall.

From there they come to the front of the engine hidden inside a metal chrome tube mounted to the inlet manifold.

At the same time, 4 wires to the transmission safety neutral switch run along the bottom of the firewall from behind the drivers side splash shield.

The 4 windscreen washer motor wires are only inches away from their source so to see these is no big deal.

The windshield washer bottle was also relocated behind the passenger splash shield as that was also an eye sore (to me).

(I used an early mustang water bag secured in place by welding a couple of hooks with straps, etc)

Below, I will post pictures with descriptions in no particular order.

Again, please let me stress, this is the way "I" did it. I'm sure there are many to ways to do it. Even better ways. Each to his own.

I'm posting this page more as a general guide for anyone needing ideas on how "others" make their engine bay look a bit neater and simpler.

I have also included (at the very bottom) other mods which I have undertaken.

In closing, can I just say that I had a lot of fun making the car "mine".

And largely made possible by the ideas and knowledge of the brilliant people on this forum!


Deciding to relocate the fuel inlet to the rear of the engine

helped unclutter the engine somewhat. You will notice that all I did was take the Holley fuel rail off and put it on back to front.

I aslo kept other hoses and leads as low as possible for as long as possible.


Removing the jumble of wires from the starter/junction/regulator helps heaps towards the "neat" look.


The battery leads go through the inner skin, under the fender and out to the starter relay through a similar setup on the rear inner skin.


With horns and water bottle gone, the other inner skin also looks clean. The wires to the engine were routed through a metal tube (between the inlet manifold and the rocker cover). This hides and protects them at the same time.


Here is a birds eye view.

You can just see one of the relocated horns on the radiator support.



Big washers with grommets were also welded here under the radiator support directly under the radiator.


This is an "up" shot under the passenger fender. This is where the main battery cable got routed further down and out the rear inner sking to the starter relay. you will also notice a brown and red 6 gauge pair of wires. This is giving new life to my ammeter.


This is the drivers side "under fender" shot. Pretty straight forward.


Factory spot welds gone .It's not much of a difference, but I don't believe any "one" task did make that much difference. I believe that all the little tasks together is what gives the simple and clean look.


Power steering hoses were also kept as low as possible.


Circled is a little black plastic junction for the wires running to the front via the metal tube. I did it this way because I needed to finish the engine bay before installing the motor back in. Once in, I simply extended from there.


This is something I'm still toying with. There is a little clear tube sticking out about an inch. This is where I top up the window washer bottle hidden below (behind the splash shield). I'm still looking for a neater cap or plug or something to finish it off but truthfully, I've never used my wipers in 9 years so it is really just for roadworthiness.


One of the "accidental" benefits of mounting the fuel pump where I did and feeding fuel from behind the engine is that I can take advantage of the extra factory tubing (ex fuel hard lines) and use them for my "hidden" vacuum tank. (next pic)


The tank is just a metal fire extinguisher cut in half and sealed.

(N needed unless you have too much overlap from the cam)


One extra little hole through the skin for the low brake warning idiot light.


I made a little bracket for the starter relay to sit on. The bracket bolts through the original holes which were for the fuel cannister bracket.


Hard to see but here is a little cover plate which goes into the corner to hide the big bunch of wires as they go from the firewall and out through the rear skin a few inches away. held on by 4 screws.



I could never work out why Henry in his wisdom decided against wind down rear quarters on our fastbacks. Anyway, I made it the way it "should" have been.

Tutorials have been written up since on this procedure so no need to elaborate here. All parts bought on eBay.


I also added some "bling" to the rear deck to give it some purpose.

We all know the back of the car is pretty much useless for anything else!


I added an electronic start butt because it makes practical sense. It saves on mechanical wear and tear. (OK, you got me, it's purdy!) It cost $35 from ebay. It must be wired in parallel between the 2 points on the ignition switch. Logically it is just doing what the key would have done in the crank position. Doing it this way does not circumvent my ignition switch, alarm, safety switch,etc.


Lastly, I was asked about posting some pictures a while ago about a "thing" I made to positively secure the hood from closing unintentionally under its own weight, wind, etc. One day (and also when available cheap) I will buy the correct hood hinges now that I have ram air installed. (all purchased from [email protected], Hi Don)


It simply inserts into 2 factory holes. Very easy.


This is to show the custom console I made to suit the megashifter a little nicer. Also I have finally got all 6 gauges working.








Cheers to all from down under. Jim Niki.


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