Tech article by gi_phil
This write-up summarizes how I put on-board air into my 1971 Bronco. I have a 3.5” suspension lift, a 2” body lift, and enjoy wheeling. Having on-board air is not only a nice benefit to airing up and down tires but could also come in handy for a variety of other uses (i.e. any air tools, nail guns etc.) Deciding on the proper system for your application is always the hardest part. I searched the internet and found all kinds of articles on how to do it – except for the installation on an early Bronco.
Having the CO2 tank route strapped into my bed or onto the roll bar was out of the question since room is at a premium. Continuing on my checklist, a 12-volt system was just too darn expensive for me. I decided to go with a York belt-driven compressor; they have high output and are also cheap. I found one in a local junkyard from a Volvo and bought it with the bracket for $35.00. I figured that the bracket would make a nice starting point for making my own mount for the compressor.
Having the main parts to my system, I next needed to figure out where to place my compressor and how to build a bracket. As the picture illustrates, I placed the compressor next to the battery and over the top of the alternator. As luck would have it, I happened to have a dual pulley, so I figured that running a belt around the alternator and the compressor would be just fine. I manufactured a bracket that utilizes the alternator spacer and a block bolt hole to allow the bracket to support the compressor. After fabricating the parts I used some high-temp Ford Blue spray paint to give it a factory look. I know if you try this modification that you may have a different scenario under the hood; just be patient and think it all through.
With the bracket mounted and the compressor in place, I ran into another problem. The fittings on top of the compressor are not national pipe thread (NPT). You can go to kilby.com to order the NPT fittings for your system, but they were too expensive for me. I went to the hardware store and bought a brass cap for both sides and a 1/8” thread – 3/8” hose barb. When I got home, I drilled the cap’s center out with the proper drill bit and pushed the hose barb threaded end through. I then soldered the hose barb to the cap, thus creating an adapter that works great for this application, not to mention constructing it for less than $50.00.
Note that the compressor itself puts out 4 CFM or more depending on engine speed. This is more than capable of inflating tires, but if you want more out of your system, then you will want to install a tank as described in the next section.
This step is the most costly if you want to use your new compressor as a true compressor. Some compressors, but not all, spit oil out of the discharge side; there are all kinds of articles relating to this problem. My compressor does not seem to spit oil out thus far. All of the following are needed in order to have the compressor work properly and safely: a pressure switch, safety valve, coalescing filter, air tank, check valve, and miscellaneous parts that you may want. The price tag for these components can go way up and varies by location. I suggest shopping around and using ingenuity when it comes to designing your system. I drew a picture on a piece of paper to keep me focused and to prevent the project from getting out of control.
After designing and hooking up my manifold, I needed a tank system to store air. I used two old nitrogen fire extinguisher bottles and mounted them up underneath the rear of the Bronco. I ran a ½” hard line black gas pipe down the frame rail and braced it in place. I used flex line at any movable location. With all of my fittings, I set out to plumb my system with an array of quick couplers so I can get around the Bronco with one hose.
I wired my compressor though my Painless fuse block and installed a rocker switch. Testing to see if things work is easy: just flip the switch with the key on and listen for the clutch to engage on the compressor. With all of this out of the way, I started up the Bronco and flipped the switch. I let the compressor switch cycle to its factory set pressure and plugged in a pressure gauge to see where it was. I adjusted the switch to give me 125 psi for now. I then walked around and checked everything for leaks and tightened hose clamps as necessary.