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Steven: >>>Could you describe this in more detail? I'm not seeing it. I thought about it longer after I read the next digest, and you are right...not enough detail. My statement was pointed towards the cars that would be using the factory air cleaner. The "air loop" would be created if you left the air cleaner attached to the rear plenum and plumbed the fan housing outlet (for the heat exchanger) to the summer/winter valve (where the heat duct would normally go). You would not have an "air loop" if the only air supply to the air cleaner was from the fan housing, but in this case, the carbs "may" steal air from the cooling flow. I have my fan housing outlets (for the heat exchangers) plugged off. Therefore, I am getting maximum air flow over the cylinders and heads. I would think you would not want to compromise the cooling system in any way...even a small percentage...don't let any of that air flow be used for any other task. Think of it like giving blood. You don't feel quite up to par for awhile. I wouldn't want my poor overworked small horsepower plant working hard when its not feeling well. >>>The air for the right heat exchangers ordinarily dumps into the cabin or out the front exchanger anyway, so in this scheme it's diverted to the carbs. The purpose here would not be pressurizing the intake to anything like the degree that a turbo or supercharger does, but just to fatten up the air supply a little to maybe compensate for the relatively small intakes at higher rpm. All just in theory so far, of course. The normal pathway of the air through the heat exchanger then into the cabin only happens when conditions are cold,...when the engine doesn't need as much cooling because the temperature differential between ambiant and engine is the greatest. It takes alot of energy to pressurize air that is being consumed. I don't think the cooling fan could supply enough volume or pressure to gain even a couple psi at the carb. In order to obtain 1 bar pressure (approx 14.7psi) you must double the volume of air in the same space. (Some other engineer may want to correct me here - I am not that good on the fluid dynamics). So if the carbs used 300cfm, you would need to supply 600cfm to obtain 1 bar? I know that 1 bar of supplied pressure translates into a big gain in horsepower (since most turbos/super chargers run around .5bar) but this is just an example. So just to supply enough air to feed the carbs without a pressure increase (this example =300cfm) would result in a 21% loss in flow for the cooling. Thats a big deal!! I hope everybody understands this and drops the issue of plumbing the fan shroud to the carbs. Unless I am completely off base here. Brian Schlepp 69 Fasty - "Purple Passion" ------------------------------------------------------------------- List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org