What exactly does this do? And why does it blow hot air right onto my Air filter intake tube...?

 

The exhaust manifold warms up quickly. This means the carb can get warm air pretty quickly as well. Warm air entering the carb will warm up the carburetor. This causes the choke to open as soon as possible and reduces emissions during warm-up phase. Also, the warm air entering the engine / combustion chambers, helps the engine more quickly than cold ambient air also reducing emissions and internal wear to the engine parts.

There should be a valve on the air filter housing with a vacuum line back to a thermoswitch on the intake that causes the valve to open, and pull air from the end of the snorkel instead of through the stove once the engine is warming up- about 90F or so.

 

Interesting, but the hot air that goes up through the little stove still would warm the air filter housing, wouldnt it?

 

well, maybe. but if the butterfly valve on the air cleaner housing closes properly when the engine's warmed up, there's not much air flow up the stove pipe. most of the heat to the cleaner would get there via conduction up the metallic stove pipe, but the radiator fan blows a lot of air back across the engine and that will cool that pipe down quite a bit.

 

Hm.
Good enough for me then
I was just wondering, because having a "warm air intake" is kind of dumb.

 

Well, it may seem dumb, but if it ever gets cold out, having the engine warm up in half the time is a good thing if for no other reason than the heater, and warm air in the intake (at least when it's cold out) makes it harder for the carburetor to ice when it's cooler out. That's when moisture in the air freezes on the carburetor, or moisture in the fuel freezes, causing the carb to no more worky.

 

True.

 

btw, I believe the correct terminology is "Pre-Heater Duct"

 

Heat Pipe off manifold shield thingy, is much funner

 

I kind of like the "mofo tube from the exhaust to the air filter."

 

heh i likey that one.