Hi am am only 17 and want to put a 4 bbl on my 68 f250 what would b the pros and cons of putting one one on....i now have a big holley 2 bbl 500 ....would i get a big increase in hp and more mpg if i keep my foot out of it..i know i really
wont get good mpg either way

 

The problem on the 360 isn't getting air and fuel in, it's getting it out.

Having had both 2bbl and 4bbl, in your situation, I'd go after the exhaust. At the very least, a good dual or large diameter single system.

You would not get any big increases with just a change to a 4bbl, especially since you have plenty of carb on there now.

Heck, I'd even go back to a stock type carb if mpg is your concern.

 

I'm toying with getting another 68-72 v8 and trying a spreadbore carb on it. I never ran mine with the 2BBL, the 360 was rebuilt before it went in, and I put an iron 4BBL intake on it. A best of about 12mpg, but plenty of power. Dual 2.25" exhausts with Flowmasters, so it ran and sounded nice. Headers would have helped for sure, but just weren't in the budget.
A spreadbore would give a nice mix of throttle response, power, and potential for economy.
Has anyone tried a Holley 390cfm?

 

I am afraid you would be highly disappointed. I had always heard adding a 4 barrel would pick up mpgs & power, well it did neither. I am big on the FE engine, love the pulling power, economy aint to be found.

Some big issues, your engine was designed in the 1950s when gas was less than $.50 a gallon, your truck weighs in the 6500lbs range, the square frontal is like pushing a box down the road. No idea of what your truck has in it today, but the 360 is a low compression early entry in the smog control world.

Headers and dual exhaust are a good place to start, rebuilding the engine to a 390 with a rv cam can increase the power, but at the end of the day the old truck is gonna be a hard drinking ol red neck with no finesse.

I suspect you like most 17 year olds (I have raised 3) don't have a lot of jingle in your jeans, so you are going to have to work a lot of overtime to work on the old truck. I suggest that you just drive it as is, have some fun.



John

 

True words and my thoughts too. The truck won't get anything over 10 mpg on a good day, running with a tailwind. You won't find any lost power with a 4bbl carb either. The motor doesn't make much power over 3000 rpm no matter how much fuel you try to pour in it.

 

freightrain and jowilker have covered my thoughts pretty well-

everybody (not just you, trust me) seems to buy these things, and immediately try to turn it into something fit for a drag strip. big carbs, 4-bbl manifolds, etc, etc.

you can learn a LOT by just getting it into proper stock running shape. and you'll be saving tons of money.

 

I already have exhaust on it with headers dose have a rv cam in it....not too worried about mpg becaus i work for a land scaper in the summer... just rly looking for more get up and go..i know it wont have that much because it has 410s

 

The 360 was not designed as a race motor, it was designed to be a stump puller. That's why it's in that F250. My '69 F250 has one. They don't make lots of top end HP, but they make a lot of low end torque. Draft horses don't make good race horses.

 

There is a 74 360 in my 65 F100. Now I already know that if I want more power then I should pull the engine and turn it into a 390. Same mpg but more HP and probably more torque. However, I have a very smooth running 360 in a truck that runs between 1500-2800 rpm or 35-65 mph. more power isn't going to change how my truck runs in that range and besides a 65 truck is not something I want to mash the pedal in anyway. Given that I have simply put on a decent size single exhaust, modified the advance curve of the distributor and use a well tuned Autolite 2100 that was rebuilt by Jon, at Pony, two years before he passed away.

 

Sorry bud, I don't think it's gonna happen, & I know that isn't what you came in here for. You will be able to haul a lot of stuff for your boss with it though.



John

 

Probably not a fair comparison due to todays fuel and speed limits but let me relate. My first FE was a brand new 1974 F250 4x4 with 4.10 gears. It was a real turd and typical 70s quality control (or lack there-of) It would get around 12-13 mpg. and run 85 flat out. I put a cheapo set of cyclone headers on and uppped the mileage to a solid 14 and got over 15 a few times. And the top end went from 85 to over 100. I still contend the headers are the first place to improve performance and the best bang for the buck, if you want to deal with headers. If you're only getting 10, I'd first suspect too heavy of foot but if you are mostly driving in the city, it's all you can expect.
To answer your question, a good dual plane intake and a well tuned 4 bbl., like a 600 Edelbrock, might get a little better mileage if you keep your foot out of it and have a little more power. For better mileage, you might try a 350 Holley. My old 69 390 ran real good with one but it will want more at higher rpms. That was a crew cab with 3.73 gears and got 12-13 running freeway speeds. BTW, it went across the scales about 4600#, not 6500 and it was a crewcab with reinforced frame.
As all of use with experience know, any gains you get will be small. 12-13 is about all you can ever expect.

 

Yes, these trucks are light. Mine with a 1200lb diesel up front and 230lbs of me in it goes across the scales at 5200.
The exhaust is a major restriction point on the FE. The manifolds are horribly designed, especially the right side one. The lack of balance between the left and right doesn't help. Headers are not made for some trucks, though, but headers aren't overly hard to make. It would be a hard job to do worse than the factory on those.