If the float is one of the polynitrophyll closed cellular foam (whew!) units, it may be heavy; as they occasionally absorb fuel.
There may be "gum" or "varnish" (modern fuel residue) on either the fuel valve plunger or the float arm, causing either to stick.
The fuel tank vent may be clogged; and in hot weather, the expansion of the fuel when heated may cause pressure on the tank, thus overdriving the fuel valve/float combination.
Other possibilities exist.
As to the float valve clip: the little hole(s) in the float arm that appear to be where to clip the clip should NEVER be used for that purpose on Rochester carbs!!! On various models, the clip should be installed over the front edge, or much more likely over the back edge of the float arm. After installing the fuel valve, float and clip, and setting the float drop; ALWAYS orient the casting in the normal configuration (on a two-barrel turn the airhorn right side up) and gently work the float from full open to full closed a few times to check for plunger bind. If the clip is properly installed, the plunger will not bind.
Jon.
Good carburetion is fuelish hot air Owner, The Carburetor Shop LLC
