'68 fastback 440 wiring harness to suit

[peterOZ]

Hi, i performed a search here prior to posting but cannot find similar question.

Being over 50 year old car i am looking at replacing all harness (i believe 5 piece off memory) to be safe and avoid any future breakdowns.

'68 fastback 318 car to 440. Car will be street / strip. What harness are you guys using and recommend?
I Will be running MSD , i imagine new harness will be set up for Volts opposed to Amps.

If i run l.e.d headlights (pending how good of a light i can get from stock to begin with) is this irrelevant to what harness i get?
All factory features on vehicle will still be operational. ( Radio, blower fan, gauges ...)

Thank you in advance with any guidance

 

[jazak5]

a 383 big block a body harness//or a NOS M code you can get plug and play led headlights so thats moot

 

[Mattax]

My suggestion is to assess the conditions, then replace as needed.
Engine compartment usually has the most damage from heat, atmosphere, and mechanics doing work.
Assuming this is a US export, LHD. M&H probably makes the best. Regardless, save the original for reference and parts in the future.
*Engine harness for '68 big block.
*Battery cable harness which also includes starter solenoid to starter wire. (Not sure M&H makes that one, but others do. If using a ministarter, some of the replicas are too short reach without strain.
*Transmission on a '68 is probably just the the neutral safety wire, although depending on when it was built it might have the reverse switch wire as well. Very imprtant to determine which arrangement your car has or will have.
*Battery Ground (earth) is seperate cable. Using one with a body ground will not hurt and can help.
* Engine to body ground.

* Instrument Harness. This is the critical one on the inside. It includes the main feeds.
There is no reason to get into converting the ammeter to a voltmeter unless you are adding electric loads (EFI, electrc fans, etc). Alteration is not plug and play.

* Console, if your car has that option.
* Body - this connects at the driver's footwell and goes to the interior lamps, tail lights, fuel tank sender, and reverse lights.

MSD 6A or 6T. You will need to make up a wiring connections.
Distributor. Points distributor is easier - connector to mate the white MSD wire.
Magnetic pickup - Must properly get the pair of wires connected with the correct polarity.
On/Off signal (smaller diameter red wire on MSD) Use a piggy back to connect at the ballast resistor or bolt to the coil feed wire's ring terminal after removing from coil.
Regardless, the original coil positive wire must be removed from the coil, secured and insulated from ground.
Run the MSD coils wires to the MSD.

If you want to get fancy, you can run the MSD main power (heavy red) direct from the alternator. Otherwise you can connect it to the battery at the starter relay. The load is small enough that its not major concern.

Headlights. With a decent E-code H4 (Cibie, Bosche, etc) and lamps that will draw 9-10 amps, add a relay harness. Or, if using LED, then that's probably not neccessary.

 

[Mattax]

MSD Wiring Instructions.

I don't think MSD is still supplying the terminals and plastic isolators pictured above. It was done wired this way because that way because the early systems would die suddenly and this provided a quick means to use factory system or a second box as a backup.

The battery in the drawing is representative.
Heavy red must connect to a main power source. Battery feed at the solenoid, or Alternator batt terminal are also good locations. Heavy black is best connecting to the engine block or heads.

Orange and black must connect to the coil.

On/off red can connect to the igntion run anywhere in that circuit. It draws very little current.

Here's photo.

Another way to connect the MSD on/off t othe original ignition wire is like this

Finally, a piggy back on the ballast resistor is another simple way.

----------------------------------------------------------
Getting fancy for the MSD power feed.

This way the ammeter only shows power into or out of the battery.
It also connects the MSD power closer to the power source.

The black 12 ga wire going through the firewall goes to the ammeter black terminal.
This creates a parallel feed to the main splice and for battery recharging.
I did this because (a) the original feed through the bulkhead had some heat damage (my fault) and (b) because I had the instrument panel out for restoration, so it was a good time to do it.

Its a fair amount of work.

 

[peterOZ]

My suggestion is to assess the conditions, then replace as needed.
Engine compartment usually has the most damage from heat, atmosphere, and mechanics doing work.
Assuming this is a US export, LHD. M&H probably makes the best. Regardless, save the original for reference and parts in the future.
*Engine harness for '68 big block.
*Battery cable harness which also includes starter solenoid to starter wire. (Not sure M&H makes that one, but others do. If using a ministarter, some of the replicas are too short reach without strain.
*Transmission on a '68 is probably just the the neutral safety wire, although depending on when it was built it might have the reverse switch wire as well. Very imprtant to determine which arrangement your car has or will have.
*Battery Ground (earth) is seperate cable. Using one with a body ground will not hurt and can help.
* Engine to body ground.

* Instrument Harness. This is the critical one on the inside. It includes the main feeds.
There is no reason to get into converting the ammeter to a voltmeter unless you are adding electric loads (EFI, electrc fans, etc). Alteration is not plug and play.

* Console, if your car has that option.
* Body - this connects at the driver's footwell and goes to the interior lamps, tail lights, fuel tank sender, and reverse lights.

MSD 6A or 6T. You will need to make up a wiring connections.
Distributor. Points distributor is easier - connector to mate the white MSD wire.
Magnetic pickup - Must properly get the pair of wires connected with the correct polarity.
On/Off signal (smaller diameter red wire on MSD) Use a piggy back to connect at the ballast resistor or bolt to the coil feed wire's ring terminal after removing from coil.
Regardless, the original coil positive wire must be removed from the coil, secured and insulated from ground.
Run the MSD coils wires to the MSD.

If you want to get fancy, you can run the MSD main power (heavy red) direct from the alternator. Otherwise you can connect it to the battery at the starter relay. The load is small enough that its not major concern.

Headlights. With a decent E-code H4 (Cibie, Bosche, etc) and lamps that will draw 9-10 amps, add a relay harness. Or, if using LED, then that's probably not neccessary.

Mattax, thank you for all the information . I have spoken with M&H and they have advised me of part numbers to use . I need to be getting them through Year One. Eng harness i will need is the 383 B.B as advised

Thanks again.