I have an '85 F-150 that is carbureted. The truck runs like a sewing machine, starts easily, and has good power. It now has the stock carb on it. My problem is of course gas mileage. It gets anywhere between 10-12 MPG. I have talked to some guys who advocate changing the intake and getting a four barrel carb and set it up so that the secondaries kick in very late in the pedal travel. I understand that a four barrel has somewhat smaller primaries than some two barrels, and may help some. I guess I am just afraid of upsetting the balance of the truck, because like I said the truck runs great. I keep it in a high state of tune which helps the driveability. I guess my question is, stick with what is working or take a chance and go to a different setup. Thanks for all the advice.

 

10-12 mpg is different for a 460 than it is for a 351 or a 302. We gotta know what you have.

10-12 mpg with a 302 is unacceptable, and would warrant some definite changes in my opinion.

10-12 mpg isn't good with a 351 Windsor, but it could be better, up around the 15 mpg range. Again, I'd look at re-building and modifying either the carburetor you have, or switching to a 4bbl.

Your truck is an F150, so I doubt it has a 460. 10 - 12 mpg with a 460 is great.

Also, you say you were looking at getting a 4bbl carburetor... I think by 85, all the 351 Windsors were 4bbls? Not sure. But, it sounds like you have a 302.

So, go get yourself a Holley 600 CFM 4bbl carburetor for your 302, play around with the secondary springs, power valves, jets, and set your floats and such and time and tune it with a vacuum gauge.

If the emissions equipment hasn't been butchered up and you want to keep it, you could get a 4bbl 600 CFM off a 351 Windsor High Output from this generation F-series.

No reason why you can't get at least 16 or 17 with a 302.

EDIT:

Just seen in your other thread you DO have a 302. Man, I'm good. Okay, enough boat floating.

But yes, 10-12 mpg with a 302 is pretty bad. Is this around town or highway?

I'd start with checking timing and fuel mixture. If those check out good, spend 20 bucks on a rebuild kit and see what you can get out of her then. If you can't get any better, you just might be able to do better with the 4bbl.

 

If it's a 1985 302, it's a computer-controlled engine in which case you should pull the computer codes to see how it feels about things. Here's how to do it at home:

Fuel Injection Technical Library » How To Run a Self-Test

 

That's what I was thinking, but I couldn't remember if the 302 then was an option for computer controlled or not.

Something wrong with the emissions equipment would definitely explain the 10-12 mpg he's getting.

 

If after checking the codes, as recommended by ctubutis, everything checks okay, then don't forget the simple things... i.e. dragging brakes, misalignment, low tire pressure, aerodynamic drag [roof rack, roof mounted driving lights, etc.] or extra weight [tools, etc.]. Is the choke opening completely and in a timely fashion? Do you have standard sized tires and wheels? Is your odometer correct? What about the air filter element... is it clean? Is the engine operating at the normal temperature [195F thermostat]?

Do you accelerate quickly? For the best economy, drive like there is an egg between your shoe and the gas pedal.

 

I don't think people had a choice if they got a 6-banger or 302... EFI was optional in 1985, but you'd have a feedback carb if you didn't get that.

The 351W HO and larger engines were still DSII/carb through 1987 I believe.

 

I noticed you said 195F? My understanding was optimum temperatures for a motor were 180F. Not only that, I noticed that on my after market gauge cluster (previous owner installed) that my truck always stays at 160F, even if I've been running it hard for the past hour.

 

I am going to take some of the advice I have gotten here. I think a carb rebuild may help, I'm not sure but it doesn't look like it has ever been worked on. I also need to check choke operation as well. I do appreciate all the suggestions and help I get on here. Best forum on the web!