Originally Posted by Tarboy56
Interesting comments I'm anxious to pull the intake manifold off and see what is going on my intake manifold does not get very hot even once the engine is totally up to temp. I may be blocked due to carbon build up or possibly wrong caskets.
I'll X2 Mouse Fink and add that the crossover of the intake usually gets clogged with carbon as the engine ages and becomes less to not functional.
As far as the heat riser valve is concerned, unless you live someplace that gets really cold there is little need to keep it functional. You'll find that when the crossover passages are clear; the intake gets plenty hot, very fast even without this troublesome device.
The small tube you mention is the Choke Stove. It supplies air heated by the hot exhaust to the bi-metallic spring in the plastic choke housing of the carb. It may, or not, source air from the air cleaner assembly old models tended to draw unfiltered air newer ones starting from the 1960's often took filter air. Some of these choke-stoves passed into the actual exhaust stream, when they finally burn out, they drew exhaust gasses into the choke spring housing which pretty much destroys all the parts from corrosion.