what size carbs??

[RobMcQuarie]

Darrell, Who would you have pissed off? You are offering your good advice/experience/observations. True, the 2V to 4V flow comparison may have muddied the water a bit, but I was just trying to show that carb air flow ratings cannot be taken so literally. I often hear milti-carb set-ups (2-3V and 2-4V) harshly put down as being impossible to drive and keep tuned, way over carbed, etc., misleading opinions that are often based on little experience. As you and many others can attest, multi-carburated engines can be just as fun and easy to drive as single carb ones. It's old, worn out carbs or ones that have had too many "tuners", that tend to foster the bad reputations.

True, some times the factories over carbed their engines, but not as often a folks think. The small block Ford Tri-power flows a mere 520cfm, rated in 4V flow. The FE 3-2V flows about 730cfm. The 390GT was given a 600 Holley, and the 428CJ a 735-which has always been a superb carb. Ford made sure that their carb selections actually matched the street driven vehicle very well-with a few exceptions: notably the over carbed Boss 302 with a 780, and the undercarbed Boss 429 with a 735. I have never specifically seen a different way of "rating" dual four air flow, but I have seen references to it in old Ford engineering literature. It's also interesting to watch 2-4V vacuum secondaries on the dyno. Dyno air flow usage is showing barely 600cfm, and the secondaries are already open.

Now, if you look at a hot 2-4V equipped FE with both the small carbs and a pair of the 715's or 780's designated for drag use, it will likely run slightly faster in the quarter with the big carbs, but not near as well on the street. Similarly, I have a hard time comprehending the 2500 and 2900 cfm total flow of the dual Autolite inline carbs Ford had for racing.

One can also use the 390cfm vac secondary carbs for 2-4V applications. There are numerous choices that can be made to work in different applications. Each has their good points.