There's at least 160 mph and 0-60 in 4.2 seconds in there somewhere..!

 This section deals with all things Wiring:

  1. Main Loom
    1. Loom Configuration
    2. Engine Bay Wiring
    3. Relays
    4. Fuses
    5. Ignition switch Configuration
    6. Boot Wiring
  2. Dashboard
    1. Layout & Loom
  3. Wiring, Connectors & Terminals
    1. Loom Cable
    2. Connectors
    3. Terminals
    4. Solder
  4. Power Distribution
  5. Fixing & Fitments Comments
  6. Wiring Modifications

1. Main Loom

I've worked through the two looms (the dash' and the main loom) and I have identified and labelled all the wires. Depending on how I design my dash' or position or reposition some other periphery units e.g. horns and power outlets etc., I might have to extend some wires. This will not be an issue as long as I use the correct type of wire, ampere wise. I'm not going to buy a multitude of reels of different multi-coloured wires to colour-conform with what I'm extending, I'm only going to get a reel each of black and grey. Black, being common for ground (gnd) and grey being a colour not used as a primary identifier for anything. So anything grey will trace back to the feeder colour, and black is black.

For neatness and safety, I've also invested in the correct size terminals and heat-shrink for the different wire sizes. This to ensure a proper connection and to neaten everything up and to make sure there is no exposed metal or wire. 

I've also measured the various diameters of the clusters of wires along the loom runs and have bought a selection of stainless steel "P" clips to support where necessary. I opted for 6 mm, 8 mm 10 mm and 16 mm clips.

Also, as I'm going the Speedhut not the Smiths route for my gauges, some of the dash' loom will be redundant. The Speedhut gauges us a series, feed-through power and ground and lighting set-up and they are all powered from a single switched feed, and all telemetry links are done using their own specific and individual cable which connects directly from each sensor.

As previously stated I'm going the MSD Atomic EFI route for my Ford 302 (not the carb' route,) and the sensor-to-gauge hook-up principles are the same no matter what engine or gauge type I have, so the amount of head-scratching and fiddling and tea drinking should be about the same.

i. Loom Configuration: There are three "functional" areas to this loom. The main demarcation being the big rubber engine bay grommet. The three loom parts being:

  • Engine bay wiring
  • The wadge of wires feeding the bank of relays, the fuse box and the plugs that join everything up
  • The wires that go into the boot

Loom Diagrams (actual): 

ii.  Engine bay wiring: I've seen many ways of routing this line of wires, and I've fixed mine to the inside edge of the engine bay, mostly tucked away under the bonnet lip. Then, fixing the remaining o/s wires to and across the bonnet hinge retaining bracket. For this, I used a combination of 6 mm, 8 mm, 10mm and 16mm steel "P" clips.


iii. Relays:

First I fixed in place the bank of seven relays. But, I wasn't happy with just self-tapping these to the bulkhead as it wasn't flat, so I mounted them onto an aluminium back-plate. This back-plate being secured to the bulkhead by two mounting brackets and a couple of M5 bolts. A very generous half a day's work but it was worth it as it is now easy to detach the whole bank of relays 'as-one' (if I need to.)

I toyed with the idea of having a bank of 8-10 relays but there is only enough room for seven [comfortably] in a row. I will need at least a couple more; one for the Pilgrim starter button and one for the heated seats. I do, however, have a spare in the supplied bank of seven as I won't be using the amplifier relay (relay nr 1.) So am undecided what to do at the moment with this one.

Made the mounting brackets from a steel bar. A piece of square steel tube would have been perfect, but I didn't have any. Each bracket consisted of a couple of 10 cm lengths of steel. The first having an M5 thread tapped into it, and the second an M8 hole. The second piece to provide a bit more distance from the bulkhead as it is slightly concave. The two individual steel bracket elements were epoxied together and fiberglassed onto the bulkhead, and the relay back-plate was bolted in place (with the relays bolted onto it.) Everything ended up flat and level and secure and is now easily detachable... job-dun.


 And finally, It's in place and looking quite neart.. 

I also made another relay mounting bar to take four extra relay units. This for the 40 amp starter button relay and the heated seats relay; which leaves a couple for future use. Notice also the 50 amp master fuse holder is on a metal backplate. Am really not a fan of having electrical conjestion spots in direct contact with GRP or plastic.

The two bus bars (just below the heater outlets) are for common distribution of 12v live (from the battery) and for 12v switched power from the ignition switch. This keeps all the 'same' in the same place. And finally, I've installed an additional eight-way fuse block. This single provided a central point for all the fuses. I will need more so it makes sense to colocate them alongside the loom fuse bank.


So... all the electrical safety and distribution gubbins are located high up in the passenger footwell area. Am happy with this.

iv. Fuses: The additional stand-alone fuse box unit is similar to the one that came with the loom. Eight fuses are really not enough for my configuration. And having a second unit in the same place as the original makes it easier to [electrically] manage things.


Fusebox Plan Actual

v. Ignition Switch (Configuration): I've sourced, from my local scrappy for a fiver, a proper (female) connector plug for the Vauxhall (male) ignition terminal plug. Here is a matrix of how it connects with the main loom plug (plug A (21)).

The colour coding and indicated use is from the GD documentation

(Sourced female plug and Plug 'A' (Ign switch connector plug) on the main loom)


The only terminals I need to be concerned about are terminals are terminals 3, 4 and 5. These being live for key position 2.

Three options for connecting things up (as far as I can make out):

  1. Connect up all up as per the GD guidelines
  2. Distribute the load over the whole ignition switch to spread things about a bit
  3. Have a bus bar in place to distribute the 12v switched live from a relevant ignition key position

Option 1 essentially supports the LS engine route and is okay for a Ford route too. Option 2 is doable too. But I like option 3 as it will simplify things greatly for my configuration. However, I will be putting the ECU on its own 12v ignition feed (possibly terminal 3) as, with respect to my MSD ECU, it is recommended to have it's own separate feed because if the ignition is off, and if the fan kicks in, the fan motor will create [induce] a back current which could (according to MSD) eventually burn out the coil if the fan and ignition are both on the same circuit. So I'll be putting the 12v switched ECU power wire on its own feed terminal to take away any chance of this back-current condition happening.

vi. Boot Wiring: The wires for the boot i.e. lights, number plate etc. are fed in from the tub. And luckily I didn't need to cut a chunk out of the passenger side cockpit back panel to feed the cluster of wires into the boot as there was a small hole going from the boot into the cockpit area at the perfect position. This is where the body is joined to the tub; there was a small gap there which served as a conduit into the boot area. So, from within the boot, I fed the wires through from the cockpit side. It really was as simple as that.

This picture shows all the boot hookups for my installation. Notice the double-earth reverse and fog lights [blacks] plugged into an unused earth. The bunches of wires (top left) are all surplus to [my] requirement as I don't have the fuel pump in the boot. Also, I've no need to use the offside fog and reverse lamp (RY & BN) connections and these are just extensions from the near side cluster.

2. Dashboard - Layout and Loom

As the dashboard is the life-support monitoring-and-awareness centre for nearly everything, I've documented all things "dash" within a separate and specific Electrics - Dashboard page. There is some overlap e.g. steering column and fitting, but essentially the dashboard needs its own separate document as it' brings everything together.

3. Wiring, Connectors & Terminals

i. Loom Cable: The majority of the loom cable consisted of just two sizes:

  • 16.5 Amp - Thin Wall Cable (30/1.93 mm (best estimate))
  • 25.0 Amp - Conductor Spec (28/2.46 mm (best estimate))

I needed to source a supply of cable for my modifications and extensions. Black for gnd (16.5 & 25.0 Amp sizes); and grey (also 16.5 & 25.0 Amp sizes) for most of everything else. I used grey as it is not a primary colour on any of the looms, and of which can be traced back to the original it's joined to. And black is black... I also used red for some power feed extensions or modifications.

ii. Connectors: A pack of Lucas style bullet connectors came with the main loom. Also, the lights and some of the loom endings had brass bullet fixings already crimped on the ends. And having seen how these function I was not happy as they were very exposed and susceptible to all sorts of environmental influences, and during my efforts to fit them I had to bend some of the 'grab' connector sockets to make the bullet end fit... I really was not impressed with the functionality of these so I changed them for more stable spade connectors.

iii. Terminals: It might seem a bit of overkill to write about terminal sizes, but I found that if the wrong size was used i.e. if the bit you crimped was too big with respect to the wire size that was being connected, I found the hold on the wire was doubtful. So I bought the correct terminal size for the wire size I was using.

Terminal types and sizes used:

  1. Spade (Open Barrel Female): (Clear plastic sleeves were used on these too)
    • 6.3 mm: These for the 25 Amp cable or for when I needed to join two thinner 16.5 Amp wires to the same connector
    • 4.8 mm: For the 16.5 Amp cable
  2. Male Blade Terminals:
    • Blade Width / Cable Size: 4.8mm / 0.5 - 1.5mm²
    • Blade Width / Cable Size: 6.3mm / 1.5 - 2.5mm²
  3. Ring Terminals:
    • 5.3 mm hole diameter for cable size 0.5 - 1.5mm²
    • 5.3 mm hole diameter for cable size 1.5 - 2.5 mm²

ivSolder: Did some practice soldering, and I'm glad I did as this seemingly routine activity could have turned out to be a major problem area. I restocked, from a well-known internet website, in readiness for me joining-up my car's electron-providing arteries... And it was absolute rubbish... An utter crap product. It wouldn't take to a wire like the stuff I was just about to run out of, and when I did manage to get it to wick into a wire, it dried with a milky, hazy surface; not a shiny one as I'm used to... I was not happy with this at all..!

This milkiness could be attributed to a couple of things:

  1. Lead-free solder: This was not the case as it was not lead-free so I discounted this as being the cause. Note... I also didn't go the lead-free route because there is a greater risk of it not creating such a good electrical connection.
  2. Poor quality solder: Am going with this one... Don't know why it was so crap and I have no way of finding out as it's in the bin.

So... having dumped the milky stuff, I sourced some very nice silky 60:40 tin/lead solder locally, and it was a pleasure to watch it flow and caress around and into the chestnut coloured strands of copper; it, congealing sedately and serenely creating a very shiny and very conductive joint... (I really need to get out more!)

Made a very useful pair of helping hands too... 

4. Power Distribution

This is where I am at the moment


5. Fixing and Fitments


  • When fixing the connectors, I used heat shrink (the type with the inner adhesive lining) after I wicked some solder into the crimped joint... (Total over-engineering, but I'm happy with the outcome)
  • As I've routed my front lights wiring and the engine loom along the inside of the engine bay, there is no possibility of the joints getting sprayed with water or muck from the wheels but I replaced all bullet connectors with covered spade connectors
  • I also put PVC cable sleeving on all exposed wires e.g. the two wires from the front indicator lights are now all contained within a single protective PCV sleeve
  • The only exposed connections are the earth bullet types on the front indicator lights. Not sure what I'm going to do to protect these from the elements yet
  • When crimping ring terminals I found the insulation tended to split. Was not happy with this so I replace the insulation with heat shrink. Not too big a job and it allowed me to wick a drop of solder into each joint as an added holder and conductor

6. Wiring Modifications

'gnd' Wire Modification in Relay nr. 5 (Horn): My first modification was to a wire in relay nr. 5 (the two joined purple ones.) This to provide a required gnd [return] as the horn relay need to be a switched-live as opposed to a switched-earth.

The original configured purple was looped from terminal 30 (12v live) back into terminal 86 (gnd) so there needed to be a gnd return in this relay. The gnd feed was fed from relay nr. 6. so I looped this into 5 and then into 7.

Snipped off the surplus-to-requirement purple wire and replaced it (in terminal 86) with a gnd extension from relay 6; which I continued and looped it into the gnd terminal of relay 7 to complete the modification. Bit of tape to neaten it all up and job done.



MSD ECU Fan Control: I modified the GD fan relay wiring (relay nr. 4) by replacing the black/green (gnd (85)) with the ECU fan control gnd wire (the pink wire.) The ECU takes care of the fan implementation as it also has the feed from the water temp' sender.

There is also a facility to control a second fan or a booster capability on a single fan from within the ECU, so everything is in place for future tinkering.

Washer Pump: The washer pump was originally configured as a 'switched earth'. With the Vectra steering column this becomes a 'switched live'; so the green wire needed to be replaced with an earth. Took the earth from an unused gnd from the dash loom... Neatened up the wiring a bit too.