Depending on who I speak to, some say the single barrel carb is better for mpg, others say a 4 is. Would it be worth it to swap out the carter for a 4 barrel, and what would it do to the mpg? Also how hard is it to set up headers? I have a 1984 F150 with the 300, 4 spd and 4x4.

 

Do you have an intake manifold for the 4 barrel ?

 

Installing a set of headers on these engines is ALOT of work. Sometimes, alternator brackets must be cut for clearance, your starter will be sealed in place (unless maybe you have a mini-starter, but I'm not certain about that.), you'll have to almost totally re-do your exhaust system, and if you plan to keep the catalytic converter, that's a custom job too. Also, if you still have to pass emissions in your state, you won't stand a snowball's chance in hell of passing emissions with a set of headers. Many people complain that they keep having exhaust leaks at the header gasket, some people are constantly re-torquing the header bolts/nuts to stop the exhaust leaks, but then there are some who don't have problems with keeping the bolts/nuts tight.

So, are they really worth all of that? Now that's a personal opinion. If done right, headers can be great on these engines, they flow great, and they definitely have a sound that's out of this world. However, if you want an infinitely easier, simpler, and more durable solution to the restrictive stock exhaust manifold, go with a set of exhaust manifolds from an '87-'96 4.9L. They're basically shorty headers, and bolt right to the engine (in some cases, with only minor modifications).

Me? I'm gonna do more research, figure out what I can, ask some more questions, and I'll still probably wind up going with the headers, if I can figure out how to do them the right way the first time without having to worry about it down the road.

 

A 4bbl can definitely net just as good, if not better, gas mileage than the stock 1bbl. The thing that kills gas mileage with a 4bbl is the ability to put more gas through it as a moments notice. They have the capacity to supply more fuel on demand, which is why they add more power.
So, you have fun stepping on it, and your gas mileage goes out the window.

If you have, say, a Holley 390 and never use the secondaries, you're only using half the carb, or 195cfm. The stock 1bbl is around 190 - 210cfm, so its pretty much the same.

Of course, that all depends on how well it's dialed in and tuned.

 

I do not have to pass emmission due to the age of the truck. I was more thinking if it wasn't too much to do it, may or may not do that. As for the four barrel, I do not have the intake currently, but have found they do not cost too much. Right not I have the single barrel Carter YFA that has the choke system pretty well destroyed where the previous owner put in a manuel choke. The manuel choke does not work too well. I have found Headers that claim not to required mods to install, but they tend to be dual outlet, which then require you to change the rest of the exhaust.

 

I'm not sure I've ever seen a set of headers for the 300 that had a single outlet.