To quote Jerry, it would seem to be a solution to a problem that does not exist???
It is my understanding that this is a modified 750 Holley, blocking off one of the primary throttle bores.
So, the 750 Holley should have approximately 375 primary, and 375 secondary. Blocking one primary should give about 187 on the primary side.
The Rochester quadrajet comes in 750, 800, and 850 sizes.
The 750 is 150 on the primary side, the 800 is 200 on the primary side, and the ridiculously expensive 850 is 250 on the primary side.
Does anyone really think that any Holley is going to even be in the same ballpark as a quadrajet for fuel economy?
But no, I have not used one.
And while in the various "other" existing options, Carter made an 800 that is 200 on the primary side.
Both the quadrajet and the Carter are "on-demand" secondary carbs, so the secondary will provide only as much as the engine requests, but 600 is available from the secondary.
Carb size depends on LOTS of variables, but the smaller primary (like the modified Holley or the Rochesters are Carters) is going to provide better primary venturi air velocity on the street. The 400 was plenty for my 300 CID Econoline.
Jon.
