I have a 1982 Born Free Class C lMotorhome built on a Ford E350 cutaway chassis with 460 engine, C6 transmission and GearVendors Overdrive. I'm replacing the Holley 4180 carb and stock intake with an Edelbrock 1411 carb and 2166 manifold. I'm also adding a duel fuel system using a Impco A2-46 right angle adaptor to mount an Impco 425 mixer atop the carb. I have another 90 degree adaptor to the top of the 425 going to a 4" hose and then to a Spectre inline air cleaner. The online air cleaner housing has a 4" inlet tube flange.

Now for my problem! I'm trying to fabricate a high flow cold air intake for this system. The original air intake on the 82 E350 uses a 3.5" square tube from the area of the front grill, just below the battery holder. This goes to a hot air switching valve (vacuum operated) that takes heated air from the heat exchanger mounted over the exhaust pipe. When operating, the flapper valve closes off the cold air intake. The cross-section of this air valve is rectangular with dimensions of about 3" wide by 2" tall, roughly 4.5" long. In the stock install, the end of this flapper valve output is connected by rectangular flex hose to the inlet of the stock air cleaner.

I have found (in my junkyard explorations) a different air inlet on the first of the EFI installations on this same E350 body style. The air inlet is mounted in the same position under the battery tray taking air from the front grill area. But here the intake tube is a simple 4" ID round tube that couples into a plastic molded right angle part that ends in a 4" flex hose (round) that then goes on to the EFI intake system. The 4" outlet is simply vertical at it's outlet and looks ideal to go to a 4" right angle hose and into my new online air cleaner. HOWEVER, there is no provision for the heated air inlet.

I'm located in Southern California, so heated air probably isn't critical for daily operation, but I do intend to traverse the USA with this beast and colder climates will definitely be seen! So my problem is how to fabricate a hot air valve to accomplish the purpose of the stock unit?? I've seen hot air inlets from Audi and other German vehicles that could easily be used to open and close the hot air inlet, but closing off the cold air intake seems much more difficult.

Any ideas on how to accomplish this would be greatly appreciated as well as any discussion about how important this function really is!