Air Intakes: Good For More Power?
Question: I have a '92 Chevy pickup with a throttle-body injection system that I am looking for more power from. I have installed headers and a new exhaust system, which helped some, but was wondering if an air cleaner like a K&N unit would make any difference.
Peter Marsh
Geneva, IN
Answer: Yes, I would think so, but there is also something else that you can do. Some time ago, a buddy of mine installed a throttle-body spacer from Airaid/PowerAid (888/876-8984, www.poweraid.com), along with an air-cleaner base from a company called Alcone Engineering (505/247-4480, www.alcone-engineering.com).
While throttle-body spacers don't always show improvements on some engines, it seems to on this one by two ways: First, by increasing the size of the intake manifold's plenum area; and second, the threadlike pattern within the bore is designed to spin the fuel/air mixture, keeping the fuel droplets better suspended. The air-cleaner base from PowerAid is quite unique in that it's more of an airbox than just a flat bottom plate. It features a large velocity stack and tuning vane that accelerates and smooths the airflow. And yes, you can combine it with a K&N filter.
Fixes For Leaky Model 20 Rear
Question: The Model 20 rearend on my '83 Scrambler keeps leaking on the passenger side. I have replaced it three times in seven months at Off Road Warehouse. Can you help me please?
Bob Rasimas
San Diego, CA
Answer: First off, there are actually two seals used in the AMC Model 20 axle: An inner seal that is pressed into the housing, and an outer seal that is held in place by the backing-plate bolts. Several things could be causing the leak. The first one that comes to mind is wear to the axleshaft. If there is a wear groove in the axleshaft, or any roughness where the seal rides, then it will destroy the seal in a short time. The solution is to either replace the axleshaft or slide what is commonly referred to as a "speedy sleeve" over the damaged area. This is nothing more than a very thin metal sleeve that is sized for a press fit on the shaft and offers a smooth surface for the seal to ride on. They are available at just about any auto parts or bearing supply house.
It also could be that the end play on the axleshafts (adjusted from the driver side with shims) is excessive, allowing the axleshaft to move back and forth and damaging the seal.
Then there is the possibility that the axleshaft is bent. If so, it would move inside the tube in an elliptical orbit and quickly damage the seal. Checking for a bent axleshaft is pretty easy if you have some way to support the axle at the end of the spline and out at the bearing. Then all you have to do is put an indicator of some type at about the middle of the shaft, rotate it, and check the amount of runout. A lathe works great for this. Sometimes, if you have a sharp-enough eye, you can just take a good look at the shaft as you rotate it.
The worst case is that you have a bent axletube, which is not uncommon on the AMC Model 20. This would cause the axleshaft to put more of a load on one side of the seal than the other, resulting in a leak.
Checking for a bent tube is a bit more difficult. Usually what you have to do is pull the axle down to a bare housing, and then with special bearing blocks, run a long straight shaft the complete length of the housing from end to end and check the alignment. Another way, while not as accurate but a bit simpler, is to pull both axleshafts out and clamp onto each housing end a truly straight length of angle steel that is about 5 or more feet long. You will put one piece of metal on each side of the housing clamped or bolted to the brake flange so it's about centered, then measure from the housing along each piece of angle to a given point on each one out towards the ends. With both pieces of angle being on the same plane, the housing is straight if they are exactly parallel to each other. This is easily checked by measuring between each of the marks made on the angle iron. For example, if on one end the distance measures 60 inches and the other measures 59 inches, then you know your housing is bent. I would clamp the angle to the housing in several different locations in order to determine if it's bent up and down or front to rear. Naturally, it's important that both pieces of angle are straight and true.
Oh, and be sure to check a factory service manual for the proper way to tighten the axle nut that holds the flange in place. There is a specific procedure that is very important to follow.