Dave:

Probably rebuild time. You most likely have a leaking needle valve, so gas pours down the air vent into the venturis from the top, worse as the speed picks up.

A minor rebuild kit will do you nicely -- new accelerator pump diaphram, needle valve and seat, gaskets. Don't touch anything else, just flush with carb cleaner. Unless there is varnish in the fuel bowl (unlikely these days), do the minimum.

Check the operation of the vac operated air vavles on the secondaries, too -- it is possible the servo is dead and you are sucking gas out with manifold vacuum since the air flaps don't open (like a Quadrajet).

Still think a stuck float/leaking needle valve is most likely.

Change the oil, too -- at least check to make sure it is oil and not half gasoline! I once fixed a Holley 2300 on a Dodge van with a stuck float, then when to move it, only had 5 lbs oil pressure. We drained 8 quarts out of a 6 quart pan......!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!