OK. You guys have probably answered this question a million times before (sorry) My friend has a 77 300 in his 81 F150. So far we have replaced the exhaust from the flange back with 2.5" pipe and a raven performance muffler. We replaced the one barrel carb with a new rebuilt from advance auto. New wires/plugs. It runs pretty good, but would like more. Is the heddman header worth the money? What other mods could we make to increase power? Thanks

 

... your biggest power gains will come if you "open up" the intake and exhaust. The stock 300 is very resricted in it's "breathing" and a lot can be gained through "flow improvement".

Headers or EFI manifolds will probably complete the exhaust portion for you. Then you ought to start looking at the intake & carb. An Offy of Clifford intake with a 350-500 cfm 2bbl or small 4 bbl (600 cfm - at the most) seems to work well on the 300 ( the stock 1 bbl is VERY restrictive).

A performance cam and/or head work is also a common upgrade.

You can also expect modest gains from upgraded ignition, air filtration, and other "tweeks" you can find by searching around here...

 

Carb, cam and intake manifold in that order of importance. Tose on an aftermarket, easily adjustable two barrel, or get an 4 barrel intake manifold and carb.

Just look at the carb you have......then look at the carb on a 302. I have the heddman header I like it but I wouldn't buy it unless you are spareing no expense. They are a dual outlet pain in the @ss, that wraps around you starter. Dura spark is very good, but an after market coil couldn't hurt. Toss all the emissions crap if you haven't yet.
How do you like the raven? I have two welded dynomax muffs.

 

The cheapest way to increase power is to port the head. It's cheap if you own a die grinder and can spare a day or so of time. The cheapest bolt ones....well there are none. The 4bbl intakes can usually be picked up cheap on Ebay, as also the headers.

 

im going to say a set of headers, summit sells hedmans for like $136.

then shoot for an offy intake with about a 300-400cfm carb, easily found at jcwhitney.

then i'd say cam it, crane has a decent looking cam in the Truck Power, which is another $110 at summit, or you can find any good rv-type cam, since yours is carbed you have a lot more options open to ya.

 

electric engine fan...this will buy you noticeable gains in hp/torque for not much $ compared to doing things like replacing camshafts, carbs, and manifolds. they're also quieter and give better idle cooling.