If the 68 P.I. is considered over carb. with a 735, then what about the 67 P.I. with dual 600 carbs ? Wouldn't that run alot worse than the single 68 version ?---S.
Re: Over Carburated ?? Neither one is over carbureted. The Holley is probably the best carburetor ever made. It is still used on the Nascar engines. One of my 67 GT 500's has a 427 tunnel port with two 780's and the engine can use all they have. Everything is relevant. Frank
The primaries of each carb are connected as progressive manual bores. As along as you don't stomp the pedal too quickly, this should work well. (I drove a 3-2V-equipped Mustang for years, and you get used to the manual throttle) The vacuum-operated secondaries are connected, open together and only if the engine demands that much intake. Effectively, it was a manual 600 cfm, with the possibility of opening much beyond that.
If you guys understood volumetric efficiency you would know that a dual carb setup on a street motor is WAY TOO MUCH. Dyno tuning with a single 4 barrel will net more horsepower every time!
Over Carburated You need to re-read my post. I didn't say it needed 1200 cfm, or would ever use it. A simple on-line carburetor calculator would prove it couldn't use it all. I had excellent performance from a 3-2V Holley setup on a 289HP engine for years as a daily driver, even though it was rated at 785cfm by Holley. The manual throttle gave me total control, and the ability to find the exact sweet spot for max power at all times and conditions. Cuts both ways, of course, carelessness could cause bogging. No doubt the 428 2-4V setup was quite responsive, and well able to deliver similar advantage to a skilled driver. More likely, the switch to a single 4V in 68 was a money-saving move. Shelby and Ford planned a 2-4V intake for the GT350 in 67, but it was cancelled, probably for that reason. One other factor you have overlooked, the coolness.
