carb swap
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Senior User
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carb swap
With the stock '77 460 4bbl I have as everyone knows gas milage is between 8-10mpg. I have a 2bbl from a '78 302 that has been sitting in a box for the last 15 yrs. Would gas milage improve if I were to swap? Performance is not a big issue with me but I am looking for better mpg. The biggest thing I use the truck for is towing a 22' cabin cruiser a short distance to a launch ramp.Any ever downsized on carbs before? tks.
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From: LAT 46.55501° & LON -122
carb swap
I would give it a try, especially if mileage is important. I have tried three different 4BBL's on my '69 F250/410FE, and all of them gave me worse mileage than the original Autolite 2100 2BBL. About a 2MPG difference of the freeway.
You will need to make or buy an adapter for your manifold, and probably change your throttle linkages, and possibly your fuel line. The only time I noticed any major changes in power was at upper RPM. I believe that the carb from your 302 is coinsiderablly smaller than my 390 carb, and combined with your larger 460, you may see a more drastic loss in power.
I might be wrong, but I do not think any 460's came with factory 2BBL's, so you may have stumbled upon the secret of building a gas-sipping big-block. All you can do is try. Many of us here are more conserned with mileage rather than horsepower and would be happy to hear of any positive results.
You will need to make or buy an adapter for your manifold, and probably change your throttle linkages, and possibly your fuel line. The only time I noticed any major changes in power was at upper RPM. I believe that the carb from your 302 is coinsiderablly smaller than my 390 carb, and combined with your larger 460, you may see a more drastic loss in power.
I might be wrong, but I do not think any 460's came with factory 2BBL's, so you may have stumbled upon the secret of building a gas-sipping big-block. All you can do is try. Many of us here are more conserned with mileage rather than horsepower and would be happy to hear of any positive results.
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carb swap
first off, I'm going to assume you've got the stock cast iron intake, and 4300 series Motorcraft 4 barrell carb: Now, let me tell you about MY fuel mileage on the original 460 in my ' 78 F150 Supercab, I got 15mpg all day with no change in running the a/c, city, or highway driving, it had a 3.50.1 gear and it ran on 89 octane LEADED gasoline, with the timing set to factory specs., you may have a stiffer rear end ratio, and you may be kicking in your mechanical secondaries on that Motorcraft 4300, or your timing could be off, or you may need a fresh tune-up, but unless you're carrying a load, or pulling that big boat alot you should be getting better mileage that 8-10 mpg, like I said the secondaries on your carb are mechanical, and won't come in unless you stand on it pretty hard, so I'd definatly stay with the 4v setup.
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carb swap
Thanks for the info. I'll give it a try and let you know what happens. The technicals are no problem. Adaptors no problem. I suppose the 302 carb is a bit "dry" from storage but if I take care it should still fly.
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