Introduction
Many people complain about getting mud and water in the air box and possibly into the engine through the air filter due to the stock location of the air intake tube. The stock location on a 2.9 sucks air from the grille area about 6" below the air box. By adapting the air intake so that it draws air from the cowl area allows for less of a chance of water entering the system, and since the cowl is so much higher, it is safe to say that it is unlikely that much water will enter unless the water you are driving through is as deep as the hood. The cowl area has a lot of natural air flow and drainage on both the drivers and passenger's side, which makes it a prime area for the intake.
Although this procedure is easily possible with a 4 cylinder (Ranger), 2.8L V6, or V8 conversion, we will be discussing two different methods for the 2.9L. The first method is on my '88BII with the newer style air box, and the second is on Hair's '87BII with the older style angled air box.
Version 1
What I did was remove the stock air intake tube, and cut off the angled part that attaches to the air box (stock part, in first picture). By inverting the part then reinserting it into the air box it turns up and back, rather than forward and down (perfect for cowl induction). Then after spending a few minutes at the local wreckers, I saw the air intake tube off of a 1984 (carbureted) Tempo. I used an epoxy to mount the air box side of the Tempo's tube inside the part of the BII's tube that was cut, and wrapped the joint in black tape for cosmetic purposes. Next I cut a hole above the heater blower motor the size of the square plastic opening on the Tempo's intake tube (right hand side part in the first photo clips into the hole seen in the second photo). In the third photo you can see how the whole system mounts.
Points to note are that the intake tube now runs really close to where the hood bracket enters the firewall. There is not enough clearance to close the hood on a stock truck, so this is only possible if there is a 2 or 3" body lift installed on the vehicle. Also, you will need to run a bead of silicon along the front bottom of the opening above the blower motor housing to prevent and liquid from going into the air box. I also left the stock drainage hole in the bottom of the air box to allow any unexpected water to dissipate.
Version 2 (submitted by Hair)
The first time I crossed a deep puddle with my 87 B II I found out where the stock air intake was. low in the grill, so I felt I had to fix it. Pulling the air box apart I covered the stock air inlet with a sheet of steel pop riveted in place and applied silicone. At the rear left of the air box facing the engine I used a 3" hole saw as low and as far back as possible and poked a hole. I went out and got 1' of 3" exhaust pipe and cut about 6" off and mounted it in the air box using 2 bolts and nuts through the rear of the box and used silicone to seal the new air intake. Now to the cowl. I moved the MAP sensor and used the 3" hole saw as high up in the cowl as I could. I took the rest of the 3" pipe and pushed it in to the cowl. mounting it with a sheet metal screw thru the flange at the top of the cowl. 3" ducting from the auto parts store connected the two tubes. the MAP sensor was remounted below the new cowl air intake. it works great! No one told me what to do, or how to do it. I just did it.
Written and Edited by: Ben Hart, with contribution from Hair