Throttle shafts......

Yes it is not as big of a problem on the fords for several reasons. One being the spring loaded throttle itself therefore ford didn't rely on a large compression spring putting pressure from the throttle shaft against the bore. Second the shafts themselves are about a 25% bigger than any of the competitors and about 50% bigger than the rochesters (which have a real problem). And third the material itself is better material.

It causes problems from "extra" air which the carburetor has not been calibrated for disrupts the air/fuel mixture for which is has been calibrated and can cause all of those problems that you mentioned. Its no different than adding to large of jetting only on the air side rather than the fuel side. At upper Rpms the addition of this extra air is significant enough to cause the engine to go very lean (read new engine time). At idle it really creates more of a vacuum problem. It also causes a problem as it disrupts the flow of air from the venturis and is added at the bottom of the intended air flow, therefore disrupting atomozation of the fuel droplets, this is actually insult to injury from the above problem and depending on what system or mode (idle, transition, power, or cruise) the carburetor is using can be minor or more significant.

Again with the Autolites it is not much of a problem, I have only seen it a dozen or so times in the last 20 years and is usually caused by some "hotrodder" installing dual heavy springs because some magazine told him to.

Its really hard to find wear values in any ford publication (in fact I have forgot where I did find it) but the general rule of thumb for large shafts like the Autolite is for wear greater than .010, and in my experience that is a pretty real number for throttle shaft wear, any more and it becomes an issue.

On shafts that have wear that is approaching or just at the edge, .007-.012 I have had reasonable success in moly coating and graphite coating the shafts.

Bill White
White Automotive