All these carburetors sucked up a bunch of schmutz through the tube leading to the exhaust manifold. If you take one apart, you'll see carbon (black) residue in the entire choke area. Spraying with carb cleaner will help a little. The best answer is to remove the carburetor and clean & polish the little piston (that is what stops working smoothly when it gets dirty). I've always wondered why nobody ever came up with a little filter to put between the carburetor and the exhaust manifold. Something you could replace every 10,000 miles or so would have stopped that problem for good.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end