The Stovebolt Site Forums The Shop Area Engine Shop Yep, the YF is better

Jon G. - well said.

I will add: bowl fuel level is basically a function of 4 major factors:

(1) float buoyancy (if you use the manufacturer's float, this will not be an issue)
(2) fuel seat orifice size (specified by the manufacturer)
(3) physical float setting (specified by the manufacturer)
(4) external fuel pressure (an acceptable range is specified by the manufacturer)

Probably 95 percent of the YF kits sold, are sold for Ford 300 CID sixes, which use the larger orifices (see Jon G. post above)

Changing the manufacturers specifications WILL result in a different than designed bowl fuel level. If the fuel orifice is too large or external fuel pressure is too high, then the float buoyancy (when the float is properly adjusted) will not balance the increased pressure seen through the fuel inlet. Thus the cheaper kits for the Chevrolet use the Ford valve, as there is insufficient volume to use a different valve.

In other words, using a FLAPS kit with a Ford 300 fuel valve means you are wasting your time trying to adjust the float!

Now - carburetion 101, lesson 3

Fuel is not "sucked" out of the jets into the venturi area. Air velocity through the venturi (at different points - SEE PICTURE BELOW) creates negative pressure (call it vacuum if you must) in the fuel wells, where atmospheric pressure PUSHES the fuel from the wells due to the pressure differential.

The fuel level in the fuel wells (same as the level in the bowl) will change the value of negative pressure required to cause fuel flow, and the volume of fuel flow.

More later, I have a meeting in 3 minutes.

Back from meeting

Jon.