Gas mileage?
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Gas mileage?
I know most people seem to say the 400 should get atleast around 12 mpg. In my 1977 F-150 4x4 I have only been driving it for a week or two. I filled up 3/4 tank. In less than a weeks time I'm down to 1/4 tank. I only drive to shcool and home and a few other places. I do not hot rod it. It does have a good size exhaust leak but i can't see that hurting the gas mileage and only getting 5 to 6 mpg. I have 33 inch tires on stock gears but once again I think that isn't too far off to make that big of difference. It has new fuel filters, air filters, spark plugs, wires, etc...
Any ideas?
Kyle
Any ideas?
Kyle
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Joined: May 2003
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From: Earth
I get 10-12 mpg with my stock 400 in my '79 F350. I have 4.10 gears and 33 inch tires. Driving in town or on the freeway, I always seem to average the same, 10-12 mpg.
Where exactly is your exhaust leak? When was the last tune-up?
Where exactly is your exhaust leak? When was the last tune-up?
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From: Mobile, Alabama
Originally Posted by 53fatfndr
I get 10-12 mpg with my stock 400 in my '79 F350. I have 4.10 gears and 33 inch tires. Driving in town or on the freeway, I always seem to average the same, 10-12 mpg.
Last edited by pknute; Jan 5, 2006 at 06:26 PM.
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Originally Posted by 53fatfndr
I get 10-12 mpg with my stock 400 in my '79 F350. I have 4.10 gears and 33 inch tires. Driving in town or on the freeway, I always seem to average the same, 10-12 mpg.
Where exactly is your exhaust leak? When was the last tune-up?
Where exactly is your exhaust leak? When was the last tune-up?
Kyle
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From: Earth
Originally Posted by BigBody
Exhaust leak is in the ehader. Pretty decent size. You can see the floor from the top of where the 4 tubes come to one. All the parts I lsited earlier are pretty new. Maybe a month or two. As far as actual tune up what do you mean? The timing is about perfect, carb is set pretty good.
Kyle
Kyle
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Originally Posted by 53fatfndr
By tune up, I mean when was the last time the plugs, wires, pcv, fuel filter, air filter, cap/rotor...when was the last time they were changed?
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From: Wisconsin
i have a 77 f250 4x4, 400, c6, 4:11 gears, 33" tires, headers and 4v holley carb. seems to get 8 mpg no matter what. do you know what your gearing is? there was a discussion on this topic recently, and many users listed their setups along with mileage. search this forum for "mileage" ? or similar and you will find it.
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Joined: Dec 2003
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From: Utah
Have a 400 in my 75 crewcab with man trans., 4.10 gears and 34" tires. Engine has edelbrock carb,intake and cam. Advance dist. timing as much as possible with out pinging on 87 oct. I avg 10-12 mpg, 7 mpg pulling travel trailer
Last edited by 75crewcab; Jan 6, 2006 at 06:23 PM.
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From: chicago burbs
timing has a big effect on fuel economy, too much advance causes unburnt hydrocarbons(fuel) to pass through to the exhaust. it doesn't make sense to me either, but that's the way it is.
"The timing is about perfect, carb is set pretty good."
you might think it runs pretty good, but setting the timing to stock spec and getting the carb dialed in on a gas analyzer might make a big difference. you might also notice the difference in slightly less power by your "seatofthepants-o-meter". performance engines are not set up to stock factory specs. almost everything affects fuel economy, even the thermostat, cold for performance and hot for economy. if you don't have a 192* in there now, try one and see if it helps? BTW, our engines use a special Tstat if you didn't know. it has an extension on the bottom. parts counter guys will pick the W tstat and swear up and down that it's the right one.
"The timing is about perfect, carb is set pretty good."
you might think it runs pretty good, but setting the timing to stock spec and getting the carb dialed in on a gas analyzer might make a big difference. you might also notice the difference in slightly less power by your "seatofthepants-o-meter". performance engines are not set up to stock factory specs. almost everything affects fuel economy, even the thermostat, cold for performance and hot for economy. if you don't have a 192* in there now, try one and see if it helps? BTW, our engines use a special Tstat if you didn't know. it has an extension on the bottom. parts counter guys will pick the W tstat and swear up and down that it's the right one.
Post Fiend
Joined: Jan 2003
Posts: 10,323
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From: Montana Territory
grclark is right... my 351M got crappy mileage until I had the timing set to factory specs and have the carb rebuilt and cleaned up and set up.... The 400 has all new stuff and the timing is set per the Comp's recomendation.