I recently acquired an 84 f150 that has had the engine swapped from the 460 it came with from the factory, to a 300/6. The guy that had this truck last has made a total disaster out of the wiring under the hood. Is there any way to find out what each and every wire coming out of the firewall was originally for ?

I'm eliminating all the emmission's components, feedback carb, TFI ignition, etc. I'll be running an HEI, and a standard single barrel carb. It looks like quite a few of the wires were for the original ignition, and quite a few for what looks like hvac controls?? Its a solenoid bank on the rear of the valve cover, it has wires and vacuum lines going to it. Im tearing all that out too because its already a chopped up mess. I'll probably just put the vent control on floor/defrost and somehow lock it in place.

I would like to just cut out all the wiring that I don't need so it's out of the way.

 

Here's a good website with wiring schematics and troubleshooting advice for our Bullnose trucks.

https://www.garysgaragemahal.com/

 

Pretty sure an '84 F150 never came with a 460.
I do not believe that an 84 would have even had an 351M or 400 which would allow for an easy 460 swap.

 

The decal on the top radiator support shows the vacuum line diagram for a 460. The other trucks I've looked at have had the same diagram for whatever engine they have in them. Maybe your right though, I'm honestly not 100% sure.

Edit........

After some googling it appears your right, ford didn't offer the 460 in the f150 for 84 but it was available in the f250/350. Im thinking maybe this truck had front end damage at some point and someone replaced the original radiator support with one out of an f250/350. Regardless of any of that, I still need to do what I mentioned in regards to eliminating unnecessary wiring.

 

Maybe you have an F250 then and not a F150
or
a core support was removed from an F250 and transplanted to your F150.

 

1985 wiring diagrams are here, your 1984 should be similar:

https://www.garysgaragemahal.com/1985-evtm.html

For the HVAC, does your truck have factory AC? If unsure, post some pics under the hood and of the control panel and we can help. IIRC, trucks without factory AC had cable operated doors for the airflow control and temperature.

Factory AC trucks have one cable only for the temp control. The doors in the plenum are vacuum operated. One vacuum actuator is under the hood, close to the passenger side hinge for the hood. The other two actuators are inside the cab. None of these HVAC actuators have wires on them. I suspect the ones you mentioned were part of the engine control and emissions system. See page 145 in the wiring diagrams above for more details on the HVAC actuators.

As far as the engine wiring, I think Ford designed the chassis portion of the electrical system to be the same regardless of the engine option. The different engine options each had their own specific engine harness that plugged into the generic chassis harness. This simplified things on the assembly line. Trying to sort out what wire went where will be a tall order, but do keep in mind how Ford designed the harnesses.

Sounds like you are planning to join the "Rip out all that pollution crap" club. It's not a bad things, but do be careful. Some guys like to sit above the radiator, put their feet on the engine to brace themselves, and just start yanking out any wires or vacuum hoses. You can be done in less than ten minutes. As you might imagine, this is NOT the optimal way to do it. This usually about the time they join this forum and ask why their truck is suddenly running so poorly. Some stuff you will want to keep, such as the PCV system. So please ask specific questions and post some pics, and club members who have gone before you can offer guidance.

 

The 460 threw a curve ball at the beginning of this thread. More than likely you have a original f150 that came from the factory with the six. If that is the case, you have the very common computer control system on it, yes I would get rid of that.

First thing you need to do is buy your HEI unit and a knock-off 1 barrel carb from Amazon or Ebay.

2nd, find your original square coil. There should be two small wires going to it. One of them will be white with a blue stripe or blue dots. This is the wire you need to hook up to the HEI "bat" terminal for the ignition. Drop the distributor in and get it timed and running.

3rd, once you get it running with the new dist, then take it down again and swap the carb out. That will be a little bit of a project, and then you can tune it and get the engine running the way you like.

4th, once you get the engine running good and reliable, then you can start pulling wires out. The first thing to do is get under the dash over the trans hump and take the computer out. Take the large wiring plug off the computer and fish it through the hole in the firewall. Then get out there and start gently pulling on the large connector, disconnecting anything that keeps it from coming out. You do not need anything related to the computer now that you have changed the distributor and the carb.

That will clean it up pretty good. I would not mess with the HVAC. It has one single vacuum line feeding a vacuum can and then going through the firewall at the pass side hood hinge. I would keep this and keep it working, it's fairly reliable and easy to get going.

You may have a few other wires laying around that you may have a question about. Make sure to spell out the color and where it's coming from.