Reply to "650 Double pumper vs 750 vacuum secondary"

The 3310 has been a poor choice when used "out of the box" since the 1960s. I'm sure a good Holley tuner can set one up to work, but as they come out of the box ... no way. Not with a 351C anyway. They will be too rich in the lower rpm range, throttle response will not be crisp, power will be down, drivability is poor and you'll normally find a stumble or hesitation somewhere in the power band too. The 3310 boosters are a poor choice, the power valve restrictions too big, other orifices & passages are likely the wrong size too, and since its a model 4160 it has a secondary metering plate which isn't tune-able.

I recommend a new Holley from the HP series, a tuner modified Holley, or one of the many Holleys Ford installed in the Boss 302, 428 Cobra Jet, 429 Cobra Jet (they were 700 to 780 cfm, too many part numbers to list).

As an example, the Boss 351 installed in the Australian Ford XY Falcon GT-HO Phase III was equipped with the same 780 Holley carburetor as a 1970 Boss 302, Ford #D0ZF-9510-Z. That is a 780 that works.

-G