I'm not familiar with your terminology. What does a air cleaner flap look like? Does it fit on top or inside of the cleaner or on the end of the snorkel?
Early ones used a temp controlled lever ... later ones used vacuum to open and close the flap. When flap closes ... hot air comes off the exhaust manifold to warm your engine faster and keep it from running lean. As the engine warms the flap opens and outside air enters the air breather instead of the hot manifold air.
The drawn from the exhaust manifold ducting would prevent the motor from running rich, not lean. :16suspect
Cold Air is denser .... which means more air ... which means you would need more fuel to keep it stoich. Carburated engines cannot compensate for air density so the fuel will always be the same ... the colder the air ... the more air entering the engine ... the leaner the engine runs ... I just went through this tuning my V-Twin Buell. Basically I tuned the back cylinder (since it has the O2 sensor on it) ... and then copied the rear fuel map to the front cylinder and bumped up the fuel enrichment ... why? Because the front cylinder is running cooler on a V-twin since it's in the wind .... cooler means denser air ... so you need more fuel to keep it stoich.
With the flapper closed, the air has to come from somewhere is what I was refering to. The choke would enrichen the mixture in the case of a stock, completely functioning aircleaner system . In the case of cold air, the O2 content isn't THAT much different to make a noticeable difference in a N/A carb application anyway.
Correct ... for a cold engine Ford wanted the engine to run as rich as possible until normal operating temp was reached .... carburetor choke + hot exhaust air = richest possible condition. Found this explanation of "The FLap" The Air Intake System Last time we talked about how the fuel got to the cylinders. This time we'll talk about how the air the fuel needs to burn gets to the cylinders. Since all manufacturers do things in a different way, we'll look at these systems in general. For an engine equipped with a carburetor, this is pretty straightforward. Air comes in the air filter housing, passes through the air filter, into the carburetor where the fuel is mixed with it. Then it passes through the intake manifold and is drawn into the cylinders. The most advanced part of the system was an Air Temperature Sensor in the air intake. It was used to measure the air temperature and, by opening and closing a flap, allow cool air in through the air horn or heated air piped in from around an exhaust manifold. This was to prevent carburetor icing that would cause the car to stall and die out. It also facilitated vaporization of the fuel into the air stream. Very simple and straight forward. There was only one draw back; there was no way to accurately measure the incoming air for the proper fuel mixture. You could use an emission analyzer and adjust the fuel mixture, but that was only at idle and not under a load. At higher speeds the mixture would be incorrect. Some automobile manufacturers recommend adjusting the carburetor on a dynamometer with the engine under load.
The heated carb air system was for the sole purpose of keeping carb ice from forming in cool/damp conditions.It only worked efficiently between 43 and 47 degrees F when carb ice was most likely to form.It "indirectly" aided in fuel atomization.It did nothing for fuel enrichment,since by the time it was doing its job the engine was producing enough heat of its own to open the choke.Remember the vacuum hose off the actuator on the snorkle went to a PVR switch on the intake?? that was the temp source/switch that activated/de-activated the "flapper" in the snorkle.That PVR recieved engine heat from the coolant passage it was threaded into.Not tryin to Pee further than anyone else here, just pointing out an aspect you fellas forgot to mention.
The temperature control plate in the snorkel of the air cleaner is designed to keep the intake air at 200 F. It operates to close off cold air and open to maintain the air going to the carb at a constant 200 F. It is for carb icing, economy and drivability. Less dense air will pull less fuel through the carb - more dense air pulls more fuel through the carb. If you are racing you want COLD air going to the engine and cold fuel. If you keep them dense you get more power but you use more fuel. With heated air you use less fuel and get less power.
