What do I need and what do I don’t!

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idaho75scamp

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I have a 1975 scamp 318 backed with a 904, I am running my ignition system with a MSD 6A box, that being said nothing really electrical works on the interior of my car except the radio.

My question is what wiring under the hood can I get rid of and what do I need to keep? The original wiring harness is hacked up and basicly junk!

I have aftermarket fuel, tach, oil gauges. I really just want to clean the wiring up and not have such a rats nest!
 
If the wiring is trashed and nothing works, I would get a painless kit and rewire the whole thing. The bulkhead are a weak spot in these cars the wiring in the 70s wasn't the greatest. I'd just start over.
 
We cannot answer that since you have the car THERE and WE cannot see it. My first question would be how is your 318 built and why does it need an MSD ignition?
 
Dartfreak75 said:
If the wiring is trashed and nothing works, I would get a painless kit and rewire the whole thing. The bulkhead are a weak spot in these cars the wiring in the 70s wasn't the greatest. I'd just start over.
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Probly a good plan! However I don’t have a big budget so I’m trying to do this 100% from scratch! Using what little is needed from the original harness
 
idaho75scamp said:
Probly a good plan! However I don’t have a big budget so I’m trying to do this 100% from scratch! Using what little is needed from the original harness
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Probably not a good plan as ALL of that factory wiring harness is the same age. OLD.
 
RustyRatRod said:
We cannot answer that since you have the car THERE and WE cannot see it. My first question would be how is your 318 built and why does it need an MSD ignition?
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Hughes whiplash cam, edlebrock intake and carb is really the other things done to it. The reason for going MSD is simply because I hate carrying spare ignition and ballast
 
idaho75scamp said:
It isn’t bad due to age, the previous owner hacked wires up and I have a bunch of disconnected wires and connectors
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Wiring degrades over time from carrying current, so yes, it is old and used because of age. Plenty of cars have burned to the ground because of hacking old and new together. Good luck!
 
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idaho75scamp said:
Hughes whiplash cam, edlebrock intake and carb is really the other things done to it. The reason for going MSD is simply because I hate carrying spare ignition and ballast
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So a stock 318 with bolt on parts. Yeah gotta have that MSD. They too have failure rates and some of them are quite frequent.
 
Depending on when your 75 was made, it might still have some remnants of the 74 seat belt interlock system that was a one year disaster. If yours was an early build (August, September or October) 1975 then it likely still has wires for it.

Post up some pictures of your engine bay and your Scamp!!! I’m partial to the 75’s too.
 
The old Crane Hi-6 ignitions that can be found on eBay are more reliable choice than the new MSD units.
 
3forty said:
The older made in the U.S.A msd boxes are good. If it is made in China,I would be worried.
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It's the newer digital boxes, too. Like what are being made right now. With good parts still available for the Mopar ignition, I'm just not a fan of MSD. Never have been. I think the Chevy crowd is responsible for that epidemic and most of their stuff is slow.
 
Back to your question. I would use and I have used just a generic speed master 20 circuit wiring kit. Maybe like a 150 bucks. Or forty percent off unblack friday...
I find the kits that try to use bolt connectors like the factory. Have just another place for things to go wrong... I prefer a true hot rod kit that Eliminates the bulkhead connector and runs directly to the connections like ford did...
It's basically a fuse box with all the wires. And what I did was cleaned and reused my end connections and bought the solder filled butt connectors and the heat gun.
From Amazon...
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My favorite tool, what's a 10 AM power supply? Use as if it was the battery or even reverse hook it up. So I could make everything work before I had everything completely connected. That way you're not putting the full amprage of the battery and burning wires.

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idaho75scamp said:
I have a 1975 scamp 318 backed with a 904, I am running my ignition system with a MSD 6A box, that being said nothing really electrical works on the interior of my car except the radio.
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So some of the this may be self-inflicted?
The '75 A-body splits the power on the engine compartment side, So its not like earlier models. If you didn't know that then this where you need to begin. Study the power feeds so you know where they go.

idaho75scamp said:
My question is what wiring under the hood can I get rid of and what do I need to keep? The original wiring harness is hacked up and basicly junk!
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The power circuit must be kept. Follow the wiring from the power supplies (battery and alternator) using the diagrams and comparing with routing on the car.
The ignition circuits must be kept. One is for ignition start, and the other one, connected through the 1/2 ohm ballast runs the ignition, alternator field, and any other engine relkated doodads that were added such as electric choke, idle stop solenoids, etc.
idaho75scamp said:
I have aftermarket fuel, tach, oil gauges. I really just want to clean the wiring up and not have such a rats nest!
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In addition or instead of?
You can draw power from the switched power buss of the fusebox if there is a place to piggyback or add an additional fuse.
To light the gages, take from the instrument light circuit. You may be able find an unused connected if there were originally options for consoles or such.

Its really important to route and bundle the wires with good support, and allowance for strain relief at each connector. Study the factory wire routing and support.
In the engine bay, use wire that has insulation rated for heat and oil.
Good terminal connections use terminals that support both the conductor and the insulations.
 
1975 Standard main power and key switch feed circuit is a little different than other years.

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From the alternator power has two paths into the passenger compartment because the key switch feed (wire J1) has been spliced into R6 on the engine side of the firewall.
Otherwise its pretty similar to preceeding years. It may or may not have originally been equiped with the seat belt interlock depending on when it was built.

Ammeter indicates current flowing through it to or from the battery. Battery should only supply power during starting, then gets recharged.

More here
www.forabodiesonly.com

Re-Wiring 1975 Plymouth Duster

This is my first post, I am stationed at an Air Force base in New Jersey, originally from CT, my father passed down his 1975 Plymouth Duster to me but when I received it, there was no power running to the rear lights, front lights, or dash. Upon investigation I found a mess of wiring (including...
www.forabodiesonly.com www.forabodiesonly.com

Look through posts for pictures.
www.forabodiesonly.com

1975 duster fuse block hold down pic needed

The 75 duster seems to have a fuse block that swings down to access the fuses and then goes back up into place. Does anyone have a picture of what the whole down looks like? Is it a wing net? Is it a stud and a bolt? Any help would be appreciated
www.forabodiesonly.com www.forabodiesonly.com
 
H22A4 said:
Depending on when your 75 was made, it might still have some remnants of the 74 seat belt interlock system that was a one year disaster. If yours was an early build (August, September or October) 1975 then it likely still has wires for it.

Post up some pictures of your engine bay and your Scamp!!! I’m partial to the 75’s too.
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Before is with the chrome air cleaner
After is with the red air cleaner and fab valve covers

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T
Mattax said:
1975 Standard main power and key switch feed circuit is a little different than other years.

View attachment 1716259669


From the alternator power has two paths into the passenger compartment because the key switch feed (wire J1) has been spliced into R6 on the engine side of the firewall.
Otherwise its pretty similar to preceeding years. It may or may not have originally been equiped with the seat belt interlock depending on when it was built.

Ammeter indicates current flowing through it to or from the battery. Battery should only supply power during starting, then gets recharged.

More here
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Look through posts for pictures.
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Thank you good sir! Exactly what I needed and asked for!!
 
Looks like your Scamp had AC once upon a time too.
 
If you are willing to rewire, I would. If you are not in love with an ammeter, and I do like them, eliminate it. If you want to keep it, make sure the ammeter itself is gone through and solder/ silver braze the studs to the shunt. Upgrade the wiring. If you are going to use a "one wire" alternator, you need considerably larger charge wire. Probably should not use an ammeter with a "one wire."

Certainly eliminate the bulkhead connector. I don't know about the 74, but on my 67 it was not difficult to cut a plate which sits in the bulkhead connector hole and snaps in place with the original hardware. Just cut a hole and large grommet. If you need to pull the harness, it should all go back through the hole

Certainly provide a big solid ground stud so the unibody can be WELL tied to the battery/ engine.
 
You will need a factory manual that has the complete wiring harnesses. The "Seatbelt interlock system" Has 17 wires that I removed to start with.
Remove the AMP meter wires from the meter and secure them together. This will eliminate the major fire starter.
I will forward a copy of color codes that go to the firewall connectors which will give a starting place.
 
Love to find an example where an ammeter in a '75 actually caused a fire.
I had a '75 4 door Valiant and it did not catch fire. Not even once.
Headlights tripping circuit breaker, yes, and that was pretty much the only electrical problem with it.

If the OP's car has the seatbelt interlock, then there are simpler ways to permanently bypass it.
 
Mattax said:
Love to find an example where an ammeter in a '75 actually caused a fire.
I had a '75 4 door Valiant and it did not catch fire. Not even once.
Headlights tripping circuit breaker, yes, and that was pretty much the only electrical problem with it.

If the OP's car has the seatbelt interlock, then there are simpler ways to permanently bypass it.
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Seat belt is already bypassed. And I believe the am meter truck is done already I’ll snap some better photos of my wiring to post up tonight
 
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