Need some info. from those who know carbs.
 

I'm working on an 81' f-100. It is a 2wd model, has the 300ci 4.9l straight six, c4 3speed auto, and 9 inch rear end with 3:18 gear ratio. I might need to express that this is a Canadian built truck.
My truck has 354,188 miles on it and I feel like it's due for a rebuild primarily due to the blown head gasket. I've got a guy who is going to rebuild my engine (vat head and block, machine both, grind crank, new cam, matched set pistons to bore, seat valves and fix rocker studs that have pressed out build and paint) for $1300. This also comes with unlimited mile one year warranty. Now, while I am putting in the effort, I am getting the trans. overhauled as well. I want to put an Offenhauser dual port aluminum intake on my fresh built motor, complete with three into one dual headers.
I want to top my intake off with a new 4bbl carb, and am leaning towards the Holley brand. I need to know which one would be best for my application. It is not a ridiculous build, I am not racing. I want reliability with the advantage of romping down on it if the need arises. I am only boring to clean out the slop, so cubic inch should be relatively near stock. I have read that I need to stick with around 390-500 cfm, but do I need a mechanical secondary, a vacuum secondary, double pumper or what? I have ran this same old single barrel since I was fifteen, I'm now 29 and this is my daily driver. I'm new to the world of four barrels and am looking for some direction....please help.

First item, Offenhauser dual port intake, take a real had look at one if you can. The divider between the large and small runners takes a 1/4" high chunk right out of the intake runners. I would look at a Clifford intake. You will want to provide some kind of heat to the bottom of the intake under the carburetor.

Second item, Holley 465 cfm 4 barrel is a good match for these engines, they are not high rpm (they can be) but generate a lot of torque. If you can turn the carb so the primary throttle plates are outboard it will run smoother and with better mixture distribution. Vacuum secondaries are recommended for automatic transmissions.

You may want a mild cam, the stock cam is rather limp, and since you are replacing it anyway, a little more lift, not a lot of duration will help it breath better.

You may find the C4 won't be up to a stronger engine, they are borderline in stock on a 300, Ford switched to using the C6 and when the OD automatics came out used the E4OD on the 300.

The 300 will surprise a good number of V8 owners due to the low end torque they develop.

Double post, I have no idea why? I only clicked submit once.

thanks for the info. I found a package deal on the JEGS website that has the Offy dual-port intake, Holley 390cfm carb with vacuum secondary, and three into one dual headers with gaskets, studs and springs and a filter for $900. I'm working on an EXTREMLY tight budget, and this is the only thing that comes close to what I want for what I can afford. Really can't afford to be picky because I still owe on the rebuild and need a tranny overhaul. This was just going to be a little something more for the effort. I also have to shell out $400 for a radiator overhaul. Sounds steep, but still beats a new truck payment!
Has anyone used this package deal from jegs?

Off original topic but anyway

I don't want to put a four barrel and have to worry about heated intake and all that, is there a smaller carb that any of y'all know of that'll work we'll? I'm really liking the idea of a progressive two barrel( one barrel around time but when you push it hard the second barrel opens and it goes) its mainly a primary driver but being a young Marine and good ole country boy I like to have the power when I want it. I don't plan on anything but a new air filter and at least efi headers. Maybe one day drop a zf5 to it if I can.
Thank yall

The only one I know of would be a Holley that I saw a while back, I think it was a modified 2100 series. Other than that, the only thing big enough would be a Toyota Land Cruiser 2 barrel. You will still have the problem of everything having to go through the hole the 1 barrel used.

Semper Fi!

You should be able to get a brand new radiator way cheaper than $400. The best place is your local autoparts store. The next place would be rockauto or ebay, though you have to pay shipping. I got a nice all aluminum radiator for my 89 off ebay a couple of years ago, and it works well and it was still cheaper even with shipping. It's huge and I only paid a little less than $300 for it.

The only drawback to a "new" $300 radiator is that it is not NOS. Those days are gone for radiators of 1981. The best I can hope for is an American to rebuild my American radiator with quality workmanship that will outlast anything from overseas. Also, with this perspective, 8 years of service from a $500 rebuilt radiator trumps 4 years from a $300 Chinese knock-off.

Has anyone used one of the Offenhauser intakes that I was talking about earlier? I was checking out the Clifford intakes and noticed it has an internal water jacket that helps atomize the fuel. Does the Offenhauser 6019-DP have a water jacket as well? If not, is it a necessity for the use of a 4 barrel 390 cfm carburetor?

I have a Modine radiator in my truck, but they are out of business now. Try looking for an SPI radiator, they are Canadian built, The other option is Vista-Pro, I got one a while back for an E-250, it was all aluminum, no plastic.

If you think our trucks are bad, try finding a radiator for a Chrysler product with the Turbo-II or Turbo-III. The radiator isn't 1/3 the size, and last source was Thailand for around $800.

That's nuts. I'd run some copper line in a five gallon bucket full of ice before I spent $800 on a radiator.