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

Electrical Configuration:

  1. Main Loom
    1. Loom Configuration
    2. Engine Bay Wiring
    3. Relays
    4. Fuses
    5. Ignition switch Configuration
    6. Boot Wiring
  2. Dashboard
    1. Loom & Layout
  3. Power, Connectivity & Distribution
  4. Wire, Connectors & Terminals
    1. Loom Cable
    2. Connectors
    3. Terminals
    4. Solder
  5. Cable Management
  6. Electrical 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', and depending on how I position or reposition some other periphery units e.g. horns and power outlets etc., I might have to extend some wires; and as long as I use the correct type of wire, ampere wise it should be a straightforward activity. Moreover, 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 red, black and grey. Grey being a colour not used as a primary identifier for anything; and red being 'power' related and black being 'gnd' related. So anything grey will trace back to the feeder colour.

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 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 the 'car' loom. The demarcation being the big rubber engine bay grommet. The three loom parts being:

  1. Engine Bay area
  2. The wadge of wires feeding the bank of relays, the fuse box and the plugs that join everything up
  3. The Boot area

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 the surface was contoured; so I mounted them onto an aluminium back-plate. This back-plate being secured to the side 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'.

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).  Am undecided what to do at the moment with this one, so I'll leave as-is not to mess anything up

Made the mounting brackets from a piece of scrap 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 inner curved side of the car. The two individual steel bracket elements were epoxied together and fibreglassed high up in the passenger footwell, 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 neat 

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 gnd. The 12v switched bus is located behind the dashboard... This keeps all the 'same' in the same place.


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

iv. Fuses: I've installed an additional 'stand-alone' eight-way fuse block. I will need more so it makes sense to colocate them alongside the loom integrated fuse block. Having a second unit in the same place as the original also makes it easier to [electrically and physically] manage things.


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 functionality and connectivity matrix as to how it connects with the main loom plug (Plug A (21)).

(Sourced female plug and Plug 'A' (Ign switch connector plug (21)) on the main loom)



I've put in some electrical bus bars to make joining up things more centralised and accessible. It also makes things easier to understand what's going on. Buses are:

  1. 12v Live: To a 5 pole bus bar in the passenger footwell
  2. 12v Switched: Fed from terminal 4 on the Ign' switch. This is a 10 pole bus bar and is located, centrally, behind the dashboard. 
  3. Gnd': To a 5 pole bus bar in the passenger footwell

I've put the ECU on its own 12v ignition switched feed (terminal 3). It is recommended to have this on its own separate switched feed because; when 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. And to complement this, I've 'bridged' terminals 2 and 3. This to ensure that if the key is turned to the 'crank' position inadvertently when the engine is running, power [to the ECU] will not be interrupted.

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 loom wires into the boot. There  was a small hole going from the boot into the cockpit area at the perfect position; so, from within the boot, I fed the loom through to the cockpit side.

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 bunch of wires (top left) are all surplus to [my] requirements.

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 - Loom & Layout

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 - Loom (Dashboard) page. There is some overlap with the steering column and fitting articles but essentially the dashboard electrics needs its own separate article as it brings everything together.

3. Power, Connectivity & Distribution

(This is where I am at the moment)


4. Wire, Connectors & Terminals

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

  • 16.5 Amp
  • 25.0 Amp

I needed to source a supply of cable for my modifications and extensions. Black and red for gnd and power (16.5 & 25.0 Amp sizes); and grey (also 16.5 & 25.0 Amp sizes) for most 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 and some modifications.

 ii. Connectors: A pack of Lucas style bullet connectors came with the main loom and 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 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. And 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 didn't go the lead-free route because there is a greater risk of it not creating such a good electrical connection. Lead in solder is a good thing.
  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!)

5. Cable Management

"Out of Sight" is really not "Out of Mind"; and cable management not only makes things look good, but it is practical for trouble shooting and safety reasons too... It's also very relaxing and therapeutic.

  • 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, 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. Electrical 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 MSD ECU fan control gnd wire (the pink wire.) The ECU takes care of the fan operation as it also has the feed from the water temperature 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... I'm toying with the idea of having two fans [functioning] fans in front of the radiator to provide a more authentic look (upgrade list amended).

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 (L7).

Accessory Power Outlets: I need a couple of accessory power outlets for phone and Satnav (USB's) and for my tyre pump (12v cigarette type). So one 2 x USB on the driver's side; and one 12v cigarette type on the passengers side was the order of the day... Ideal place is, one each side of the tunnel behind the air vents therefore within easy reach, but out of the way, of anything... Didn't want these on the dash' front as they would spoil the look. Feeds are from the 12v switched bus via individual 3 Amp fuses.

You can also see the footwell LED lights (CBS LED type) too (not wired up yet though). Just stuck them to the underside of the dash’ trays and drilled some holes and tie-wrapped them in place for extra security.

I'll probably put one 12v cigarette type outlet in the boot for my portable 12v cool-box too, but not sure where yet.