One of the most time-honored rituals in four-wheeling is the airing
down of your tires before you hit the trail. The problem is that
you then need to refill them to street pressure before you hit the
highway. The obvious solution is to carry an air tank or air
compressor with you on the trail. There are several ways to do
this:
Carry a pre-filled air tank with you that has enough capacity
to fill all four tires. This gives you a limited air supply, and
doesn't allow you to help out your neighbors who need air.
Carry a $15 compressor powered by your lighter jack. This is
cheap and gives you unlimited air, but you have to wait forever. I
have such a compressor. It's great for bikes and balls, but it only
puts about 1 psi per minute into my 225/75R15's.
If you have ARB air
lockers, you can use the small compressor that powers those to
fill your tires. It's a whole lot better than the above option, but
it's still slow, noisy, only puts out about 90 psi, and costs
$200.
Companies like Curry and Ready-Air sell electric compressors
that you mount in your engine compartment. These often are setup to
fill auxiliary air tanks mounted somewhere on the vehicle. The
Quick Air 2 boasts 2.2 cfm at 105 psi and runs about $250.
The York-style A/C compressors used by AMC, Ford, and Volvo in
the '70's can be used as engine-driven air compressors. That's the
setup that I'm using on my YJ. Not only will it fill tires, but it
also keeps up with most smaller air tools.
The Tank
You really should have a tank for any good onboard air setup. This
ensures that you still have air if your engine dies, and it lets
you run things like air tools that suck more volume than your
compressor can put out. Some people weld shut the ends of their
tube bumpers, nerf bars, or roll cages and tap a hole to mount the
air fittings. For example, a 36" long, 3" diameter tube will hold
1.1 gallons of air. This is a great idea, if you have such things
on your vehicle. I don't (yet). I opted for a used 6"x19", 2-gallon
tank from an old portable air compressor rated at 125 psi. I picked
this up at a local air compressor repair shop for $30. It even came
with the necessary brackets already welded onto it, as well as two
threaded holes containing a drain plug, quick disconnect fitting,
and 150 psi pop-off safety valve. I just had to drill the mounting
holes and cut off any brackets I didn't need.
The next trick is tank placement. Some people put the tank inside
the vehicle, but then you have to run the air lines through the
firewall to reach the compressor. It's also a safety hazard if the
tank gets over-pressurized or dented and explodes. In a small
vehicle like my YJ, inside space is at a premium, so I didn't want
to waste it with a permanently-mounted air tank. That left three
good spots that I could find on my YJ:
Just behind and to the right (passenger side) of the radiator,
in front of the fender well.
Behind the right fender well, underneath the battery tray.
Under the body tub, above, in front of, and parallel to the
rear axle.
Each spot is a different shape. The best choice
depends on the shape of your tank and the amount of other stuff in
your engine compartment. I chose to mount my tank by the rear axle.
The maximum diameter of a tank in this position is 6" if you want
to avoid hitting it with your pinion yoke. When mounting your tank,
it's important to have an outlet at the lowest point on the tank so
you can drain moisture from it periodically. Regardless of what
filters you have on the line, unless you live in a zero-humidity
environment, water will condense on the inside of the tank
when it depressurizes. When I mounted my tank, I used a single hole on
the bottom "side" of the tank for both input and output. I simply
used a four-way cross connector that had the top connected to the
bottom of the tank, the hose to the compressor coming out one side
of the cross, a drain plug on the bottom of the cross, and a
quick-disconnect fitting on the other side. The quick disconnect is
a bit more difficult to reach than I'd originally envisioned, so I
may drill a hole in my tub and move it inside the cab someday. To
keep the inside of the quick disconnect clean, I capped off a male
disconnect fitting and keep it plugged into the female end when not
in use. I zip-tied the hose to the brake and fuel lines running
along the inside of the frame rail and up into the engine
compartment. The hose then ran along a lip on the bottom of the
firewall just above the bellhousing (I drilled a hole in this ledge
and zip-tied the hose to it to ensure it wouldn't fall off and lie
on anything hot. I coiled the extra foot or two of hose up under
the battery tray, and then ran the end of it under the alternator
to the front of the passenger fenderwell where the rest of the air
fittings were located. This requires about 12' of hose; I picked up
15' of 1/4" hose for $7 from the local surplus center.
The Compressor
Identification
Most A/C compressors lubricate themselves with the freon that flows
through the A/C system. In order to use these compressors for
pumping air, you need to have an external oiler feeding oil into
the intake hose and a filter to remove the oil from the output
hose. Certain York-style compressors (the big, boxy, vertical kind)
used an internal oil reservoir for lubrication, which makes them
ideal for use as stand-alone air compressors. These compressors
were commonly used on AMCs, Fords, and (I hear) Volvos in the '70's
and early '80's. Therold Enterprises makes mounting brackets and
alternator pulleys to mount an AMC York onto a current Jeep 4- or
6-cyl engine. The guy I talked to was extremely friendly and
knowledgeable about the differences in the various kinds of York
compressors. He outlined three major differences in the various
types: hose connectors, pulley clearance, and piston stroke length.
Unless you
have gobs of vertical hood clearance, you really want to get the
AMC-style hose connectors, which run horizontally across the top of
the compressor. The Ford-style connectors stick vertically out of
the top of the compressors and then bend over to connect with the
A/C hoses, which adds about 3" to the total height of the unit. The
good news is that these connectors are just screwed into the top of
the compressor, and the two connector styles are interchangeable on
the same compressor. The bad news is that the screw threads on the
connectors are closer together than those on most 3/4" pipe
fittings, so it's nearly impossible to find connectors anywhere but
on another York compressor. At left is a photo of my Ford-style
compressor. The photo shows one Ford-style hose connector and one
AMC-style connector so you can see the difference. Another
difference between the AMC and Ford versions is the pulley. The AMC
pulley is positioned very close (1/2") to the body of the
compressor. The Ford pulley sticks out about two inches away from
the body. This might make a difference in your mounting bracket
because the belt obviously needs to line up evenly with the pulley
on the other end. The third difference is in the stroke length.
There are reportedly three different stroke lengths, ranging from
less than 7" to over 10". The longer the stroke, the more air the
compressor can pump per minute. This doesn't vary by auto maker, so
there are two ways to tell which length you've got:
If your compressor still has a metal York (not Motorcraft) ID
tag bolted to the front of it, there will be a number on the tag
that looks like "F2XXY", where:
XX
Stroke length
10 = long
09 = medium
07 = short
Y
Discharge Direction
L = left
R = right
Take off the clutch and look at the crankshaft.
Remove the center bolt (1/2" socket)
Remove the large washer
Run a 5/8" coarse thread bolt in until it forces the clutch
off
Look at the end of the crankshaft. The end is flat on all
models.
If the edge of the flat end is beveled, you've got the short
stroke.
If it's a sharp corner, but with a thin groove for a retaining
clip, you've got the medium stroke.
If it's a sharp corner without any groove, you've got the long
stroke.
Acquisition
I've seen junk yard prices for old Yorks ranging from $12.50 to
over $50. I had to pay $30 for my Ford model off a late-70's
Fairmont, then shelled out another $20 to get AMC hose connectors
and an idler pulley off an AMC Eagle at a different yard. If you
can, have the yard personnel remove the compressor for you, since
the placement of the mounting bolts makes removing it from the
vehicle yourself a real PITA. When getting the hose connectors, try
to grab a length of hose along with the weird connector. This will
make it easier to connect it to your own custom setup later. Before
you lay down your green, make sure the compressor works. To check
whether it pumps air, plug the outlet hose with your thumb and then
turn the inner portion of the clutch pulley several full
revolutions. If, upon removing your thumb, you can feel the
pressure difference, then it passed the test. Ideally, there should
be no oil pumped out the hose, but a simple inline filter will fix
that problem if it exists. The second test is whether the electric
clutch works. The clutch is what locks the outer portion of the
pulley where the belt runs to the inner portion of the pulley
that's connected to the crankshaft. To check this, ground the
compressor case on your vehicle. Then take the single wire that
should be attached to the compressor and touch it to your positive
battery terminal. You should hear a click as the clutch engages,
and turning the outer portion of the pulley should then force the
inner section to turn and pump air. When current is removed, the
clutch should disengage, and the outer portion of the pulley should
spin freely without moving the inner portion.
Mounting
In order to hold oil, the compressor must be mounted vertically.
The oil check/fill hole on my York is about half way up the left
(as you're facing the pulley) side of the compressor. Remove the
bolt, then put a 90-degree bend in a section of metal coat hanger.
Make sure it's long enough so that the end of the wire touches the
bottom of the oil sump. I've seen oil level recommendations ranging
from 1" to half way up the dipstick. The type of oil used isn't
critical--regular old 10W-30 will work fine. A trigger-type oil
squirter can seems to be the best way to add oil when necessary.
Mounting the York to an old Jeep with a 258 ci
inline-6 should be pretty easy, since this compressor was available
from the factory. Just grab the OEM brackets from another 258 with
A/C and you're good to go. Mounting it on any other engine requires
fabrication of a custom mounting bracket. Complete mounting
brackets for newer Jeep engines are available for $200+ from
Therold Enterprises. If that's too steep for you, they'll sell you
just the back plate for the compressor, with slots drilled for
adjustable mounting bolts, for $12. If you're the do-it-yourself
type, you could also fabricate your own design. Craig Myers has a
good design for mounting to his '93 YJ 4-cyl
that I believe is similar to what Therold sells. I ended up with
(essentially) two 6x6x3/16" steel plates welded together to form a
T. A diagram with mounting hole measurements is on page
1. Measurements of the alternator bracket, compressor, and
pulleys without the compressor bracket is on page
2. If your engine uses newer serpentine belts, you must somehow
rig up a v-belt pulley to power the compressor's v-belt pulley.
Therold sells a new alternator pulley for newer Jeeps that has both
serpentine and v-belt grooves. This seems to be the route most
people take, but their $40 price tag was a bit steep for me. I
wandered around a junk yard until I found a pulley that would fit
between my water pump pulley and the fan mount. I got one for $5 (I
think it was from an '80-ish Chevy Caprice -- I forget
exactly) that had 3 screw holes (my Jeep has four) and a 7/8"
center shaft hole (my Jeep's was 5/8"). I took it to a local
machinist who charged me $15 to narrow the center hole with a
washer and drill a 4-hole bolt pattern to match that of my Jeep. I
considered doing it myself, but a pulley spinning at 4K rpm will
cause nasty vibrations and eventually tear up your water pump if
it's not perfectly centered. My route was a bit more work, but I
saved $20. The result required a 49.5" v-belt. The center of the
belt has at least an inch of play when I push hard, which is more
than I'd like, but a 49" belt just wasn't long enough. An idler
pulley may be in order if belt slippage becomes a problem. The
first picture below shows the pulley as it came off the donor
vehicle. The second picture shows the modifications that the
machinist made to allow mounting to my YJ. The third photo shows it
mounted in place.
If I were doing it again, I might just buy the stuff from Therold
rather than fabbing it myself. Their way uses a $40 pulley plus a
$12 plate that allows the compressor to adjust itself vertically,
guaranteeing a tight belt ($52 total). My set cost $20 for the
re-machined pulley plus $40 for the bracket (got screwed there--he
quoted me $25 initially). This cost $60 total, and I may have to
add a sturdy, adjustable idler pulley to my compressor bracket if
the belt turns out to be too loose.
Air Fittings
I chose to mount the hose connectors and stuff on the inside of my
front right wheel well near the factory jack. That location
provides easy access and also keeps everything above the water line
should I decide to ford any rivers.
The input hose on the York compressor needs to run to an air
filter. I used a $4 crankcase filter (Fram part BA3631) that looked
like it would match up well to my intake hose. A foot or so of
electrical tape fastened it to the metal part of the intake hose
connector. If your compressor leaks any oil out through the output
hose, you'll want to install an inline air filter between the
compressor and the rest of the system. This should trap any oil,
water, or anything else that you don't want getting blown into your
tank, tires, or tools. It doesn't look like my compressor has this
problem, so I opted to save $20 and skip the filter. The output
hose from the York (or the filter, if so equipped) needs run to a
check valve that prevents air from the rest of the system from
flowing back into the compressor. If this were allowed to happen,
the compressor would have to work much harder to start up
initially. On the system side of the check valve, I installed a
pressure switch. This switch turns the compressor's clutch on when
the pressure in the system drops to a certain level, and turns it
off again when the pressure climbs to a certain level. Many
pressure switches have preset on and off levels, but I found one at
a surplus center for $17 that has variable settings I can adjust
myself. The difference between on and off is preset to about 15-20
psi. I adjusted the turn on pressure to about 90-95 psi for now,
putting the shut off pressure at just under 110 psi. If you're
using this compressor to power your ARB air lockers, you must keep
the pressure between 80 and 105 psi. Next to the pressure switch, I
installed a 160 psi pressure gauge. Make sure you mount this such
that it will be easily visible in less than optimal lighting
without sticking your head down into a running engine. Mine ended
up just rearward of the right headlight, lying sideways and facing
straight up. Somewhere around here needs to be a pop-off safety
valve rated the same as your wimpiest piece of hardware. In my
case, the 125 psi tank was the limiting factor. If the pressure
reaches a certain level, this valve will pop open to release the
extra pressure before something more critical explodes. The last
piece was a 1/4" NPT quick-disconnect fitting to which I can attach
the air hose of my choosing. I picked up a 25' long 1/4" rubber air
hose at the local surplus center for $7. (The spring-coiled hoses
just don't stretch far enough to reach all four tires.) One end of
the hose needs a male fitting for the quick disconnect, and the
other end needs a female end. Don't forget to get an air chuck to
attach the hose to your tire stems. If you have a tendency to
splash water, mud, or other crud around your engine compartment (or
near the rear axle, where I mounted a second quick disconnect),
then you'll want to keep that stuff out of your air fittings. I got
two mail quick disconnect fittings and capped them off to use as
plugs in the female fittings when I'm not using the air system for
more important things. This whole mess is attached to my fender
well with an angle bracket and a couple bolts.
Electrical Connections
In addition to the pressure switch, you should also have a master
switch somewhere in the battery / pressure switch / clutch circuit
so that your battery doesn't go dead if your tank gets low while
the engine isn't running. A lighted switch run through the firewall
to your dashboard is probably a good idea. I used a big, lighted
SPST rocker switch screwed to an angle bracket on the bottom of my
dash (just under the climate control levers). Being lighted, it's
easy to see at a glance whether it's on or off, but at night, that
bright red light is quite blinding. I recommend getting a smallish
switch whose glow won't ward off oncoming aircraft. The wire ran
from the upper-left-most accessory plug in my under-dash fuse block
to the rocker switch. I used an accessory plug so that the circuit
would be switched by the ignition key; there's obviously no point
in engaging the compressor clutch if the fan belts aren't turning.
It then ran from the switch through the rubber grommet above the
accelerator through which all the other dash wires run into the
engine compartment. Just use a small knife to cut the smallest slit
possible in the rubber grommet that will still allow your wire to
pass through. The wire then ran along the front of the firewall to
the passenger side fender well and then up to the pressure switch.
The last leg runs from the pressure switch to the positive wire
running out of the compressor.
Shopping list
The actual list of supplies required will vary from one rig to
another, but this is what I used and what it cost me.
Item
Cost
Compressor and Tank
York A/C compressor from Ford Fairmont
$35.00
AMC-style hose connectors for York
$12.00
Custom mounting bracket for compressor, parts and labor
$40.33
V-belt water pump pulley from Chevy Caprice, machined to fit
'95 YJ
25' x 1/4" spring-coil air hose, 1/4" NPT fittings
$6.99
1/4" NPT check valve
$12.95
Square D Pumptrol Adjustable Pressure Switch, Class 9013 Type
FHG12J27 (1/8" NPT fitting)
$16.95
160 psi pressure gauge (1/4" NPT fitting)
$4.69
Air fitting combo kit (air chuck, blower and fittings, tire
pressure gauge, two hex nipples, female quick-disconnect fitting,
six male quick-disconnect fittings (two female-threaded, four
male-threaded)
$12.47
Quick disconnect coupler (male and female ends)
$4.49
1/4" NPT needle drain cock
$1.85
Two 1/4" NPT four-way cross manifolds
$8.50
1/4" NPT street elbow
$1.79
Two 1/4" NPT hex nipples
$1.50
1/4" NPT male to 1/8" NPT female hex bushing
$0.73
1/4" male NPT to 1/2" hose barb
$1.49
1/4" NPT square-head plug
$0.25
Two 1/4" NPT female pipe caps
$2.70
Subtotal
$93.09
Mounting Hardware
1.5x1.5" metal corner brace
$0.53
3x1" metal corner brace
$0.49
6-32 machine screws (12 pack)
$0.59
6-32 machine screws lock nuts (12 pack)
$0.59
8" zip-ties
$1.69
Four each: 1/4" washers and lock washers
$0.24
Four 8M 1.25x20 bolts
$2.18
Four 8M washers
$1.09
Subtotal
$7.40
Electrical Stuff
Lighted 30A SPST rocker switch
$2.29
15' (or so) of insulated 14-18 AWG wire
already had
Miscellaneous electrical connectors bought in bulk
nil
Subtotal
$2.29
Total
$250.81
Contributors
Many people on the Net were a great help in completing this
project. Special thanks go out to Darin
Smith, Jon Hylands, Craig Myers, and Matt Bateman for their excellent web pages and
helpful email
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Mounting the York to an old Jeep with a 258 ci
inline-6 should be pretty easy, since this compressor was available
from the factory. Just grab the OEM brackets from another 258 with
A/C and you're good to go. Mounting it on any other engine requires
fabrication of a custom mounting bracket. Complete mounting
brackets for newer Jeep engines are available for $200+ from
Therold Enterprises. If that's too steep for you, they'll sell you
just the back plate for the compressor, with slots drilled for
adjustable mounting bolts, for $12. If you're the do-it-yourself
type, you could also fabricate your own design. Craig Myers has a
good design for mounting to his '93 YJ 4-cyl
that I believe is similar to what Therold sells. I ended up with
(essentially) two 6x6x3/16" steel plates welded together to form a
T. A diagram with mounting hole measurements is on page
1. Measurements of the alternator bracket, compressor, and
pulleys without the compressor bracket is on page
2. If your engine uses newer serpentine belts, you must somehow
rig up a v-belt pulley to power the compressor's v-belt pulley.
Therold sells a new alternator pulley for newer Jeeps that has both
serpentine and v-belt grooves. This seems to be the route most
people take, but their $40 price tag was a bit steep for me. I
wandered around a junk yard until I found a pulley that would fit
between my water pump pulley and the fan mount. I got one for $5 (I
think it was from an '80-ish Chevy Caprice -- I forget
exactly) that had 3 screw holes (my Jeep has four) and a 7/8"
center shaft hole (my Jeep's was 5/8"). I took it to a local
machinist who charged me $15 to narrow the center hole with a
washer and drill a 4-hole bolt pattern to match that of my Jeep. I
considered doing it myself, but a pulley spinning at 4K rpm will
cause nasty vibrations and eventually tear up your water pump if
it's not perfectly centered. My route was a bit more work, but I
saved $20. The result required a 49.5" v-belt. The center of the
belt has at least an inch of play when I push hard, which is more
than I'd like, but a 49" belt just wasn't long enough. An idler
pulley may be in order if belt slippage becomes a problem. The
first picture below shows the pulley as it came off the donor
vehicle. The second picture shows the modifications that the
machinist made to allow mounting to my YJ. The third photo shows it
mounted in place.
Posted Jan 09 2009 01:37AM
