Hello, I have a 71 w/ a 302 and 2v carb/intake.
I have a holley 4vcarb new in the box and my dad ordered a weiand intake for me
(I'm only 15 y/oand I don't know a whole lot about engine tech.)

I have been curious about the MPG of a 4v vs. 2v.
I've been reading some topics on this and have seen that everyone says a 4v gets better mpg.
Why is this?
Like I said I don't know much but I expected a 2v to get better gas milage.

 

What CFM size is the carb?

A 4v carb can give better fuel economy than a 2v because if your not flooring the throttle then a 4v carb only uses 2 barrels, which are usually smaller than the barrels on a 2v carb. If you stomp on the throttle though, then all 4 barrels kick in and you get a LOT more fuel into the engine also your fuel economy goes down the toilet lol

 

It is a 600cfm.
Here is the carb: http://www.holley.com/0-1850S.asp

Here is the intake: http://www.holley.com/8124.asp

 

Yeah, if you have a 600cfm carb that's a 4v, then the front 2 barrels are 300cfm max, sometimes the front barrels are a titch smaller to help on economy, so 250-300cfm. As opposed to a 2v, where all the cfm is going through the only 2 barrels. 2v and 4v carbs are rated differently though, so a 400cfm 2v would actually be more like a 320cfm carb rated the same was a 4v is.

 

Just make sure your carb is tuned well, and you'll see a little better mileage with the 4v, but some of that will just be the more efficient manifold. Keeping your right foot conservative will help, too.

Also, make sure your vacuum secondaries are tight enough to stay closed at cruise RPM's, especially if your engine is turning 3k or so.

 

Ok I think I pretty much undertand now, thanks for the feedback!
Anybody know where I can order a nice dress-up kit with either a Ford or Mustang theme?

 

just make you keep the carb tuned right and go no bigger than 600cfm if its a stock motor. i had a 73 that was slightly built and had a 750 DP on it. wayyy too much gas. dowsized to 650 and still had to use regulator. 600 should be about perfect for it though. make sure you get you kickdown attatched at the exact point though or it will hold gears too long. vaccuum is also hard to tune in after changing carbs from 2v to 4v. sometimes people have to go back to 2v just because stock heads dont want to support 4v. tune it right and get some platinum plugs and a nice electric system and you wont have any problems. any questions PM me-ive been through that process several times lol

 

theres some nice catalogs for older stang
dallas mustang
national parts depot
california mustang
the paddock

theres tons all you have to do is search for them. also check ebay alot of manufacturers put stuff on there and you can find some raelly good deals through them