Reply to "In need of carb recommendations"

[quote]:
Originally posted by ttam23:
what hp gains (if any) can i expect from changing out the stock carb and manifold with a Edelbrock 2665 Performer 351-4V and a summit racing 750 carb. all other parts stock on a 1972 pre-L . From what i read on the mustang forums http://www.7173mustangs.com/th...brock-intake-351c-4v it looks like i should just keep the stock intake any thought?[quote]

Rule of thumb: going from a Holley 600 to a Holley 750 on a 351-C will increase bhp by about 30 and decrease mileage by about 3 mpg. This is without fiddling with jetting or ignition timing- just a straight bolt-on. Various intakes can be a little better or worse but do not markedly change the above rule. And if the Summit 'racing' carb you have in mind is a double-pumper, the mileage drop will be more, since DP carbs are set up rich out of the box; you are expected to re-jet; in the meantime, you will not blow up your engine and cause warranty claims running rich.

I'm reminded of a mid-west Pantera owner that added a Holley Dominator to his stroker-351. He said "The Dominator looks trick and makes lots more noise but goes slower and now I get 8 mpg; want to buy a carb cheap?" A Shelby Mustang owner I know tried autocrossing: the engine had an 850 DP for drag and road-racing. As he went down in carb size, his autocross times improved; today, he still wins his class using a Holley 600.

Professional carb tuners make some 35 major & minor changes inside DP carbs to tune them for a given engine combo, usually on a dyno. With a tuner-DP, you CAN get decent mileage AND extra power. But not out of the box. My Holley tuner- 700 DP gives significantly more power AND 20 mpg in our modified 351-C. A lot of Pantera owners have found this the hard way, so don't dispose of your smaller carb. You likely will want it back some day.