[Grady Clay]

Actually the easy part you can do.

Take some of the red, wire-wound, silicon tube and hose-clamp it to the ‘flapper valve’ outlet. You can cut the hose for the control wire bracket.

I route hose ahead of the axle and then angle rearward. I made two little holes in the flange of the heat exchanger and bolted on a small support bracket. I used safety wire everywhere as it is too hot for zip-ties and more big hose clamps are too heavy.

Make sure it can’t come near the battery B+ terminal on the right side or the throttle linkage on the left. You need real wire restraints for these.

Mine touch things like the parking brake cables, heat control cables, trailing arms (slightly) and even the axle shaft (not boot) occasionally under extreme use.

This effort takes all that very hot waste heater air (and it is VERY HOT) and blows it down and back under the engine.

Not only does this keep the rear brakes cooler but it also reduces the temperature of the transmission and starter. We were doing this in the ‘60s. I think some 993s vent the waste air down and back.


When doing this, consider how it might fail. Most dangerous, I think, is to get wrapped around an axle and interfere with the throttle or short to the B+. (Make sure your B+ has a good boot zip-tied in place.)


I think there is still room for your down-facing NACA-Duct under the torsion bar tube and hose toward the brakes. Be sure nothing can vibrate against a brake pipe or hose. Keep in mind that as the suspension goes ‘up’ on ‘bump’, there is almost no clearance to the underside of the chassis. The tube will probably need to end before the inboard side of the chassis. That should be enough.

Inspect regularly. Adjust as necessary. I consider all this ductwork as disposable and install everything new periodically or when you have the engine/trans out.

Best,
Grady