gas mileage for a 250 cid

[Anonymous]

I know i ask a lot of questions but i want to make sure i make the right decision. I am considering getting a 69 coupe with a 250 and a c-4, 2.75:1 rear gears.

What is the gas mileage for a stock 250 cid engine? About how many more MPG would it make if electronic ignition, a free flowing exhaust, and an open air element with a k&n air filter were added to the car?

Thanks.

 

[Anonymous]

So many variables involved in economy but I believe it should fall somewhere between 21-25 mpg cruising. That reading is taken from and Aussie log head 250.
The 2V 250 does about same on open road but that can drop quickly when the pedal goes down.
Cant tell you what you would get with your changes but I doupt you would get much more than a carb running at optimum efficiency at cruising speed. Apparently some of the crossflows can get close to 30 mpg with the weber carb.

 

[xctasy]

In US mpg, 21-25 is 17.5 to 20.8 mpg.

The British decided that a gallon should be 4.545 litres, not 3.7 liters. Just like putting the i in aluminum for the new word..aluminium.

 

[Anonymous]

Tatao, your mileage will vary according to where you live and how you drive. If you live up in the San Sal area you might get 15 mpg driving around town. Down on the coast you might get 20, while up in the mountains you'll be lucky to get 12, assuming a properly tuned stock carb and tight tranny. In SA many folks throw away the Motorcraft carb and use a single barrel from a Mazda 1.8L I-4.

 

[Anonymous]

Made a mistake there, the gears are 2.79:1.

What mods or things would have to be done to the engine in order to get say about 20 MPG in city driving?

Or is it impossible to get that kind of gas mileage from one of these engines? My grandma has a 79 chevy caprice with a 250 and she gets about 10 MPG, that's why im asking if it is possible. I might get the 69 coupe with a 250 but i want to know what gas mileage im gonna get in city driving since i drive about 40 miles in the city every day and what i can do to improve it and get about 20 MPG. Gas mileage is really important to me.

 

[Anonymous]

The toughest part of improving your city driving fuel mileage is that in city driving one is constantly accelerating, which burns extra gas, and much of San Salvador isn't particularly flat, which will burn more gas than if you were on flat ground like down on the coast. When I lived in CA and SA, most of the folks I knew with Mustangs had gotten rid of the Motorcraft carb and replaced it with a tiny one-barrel carb from a Mazda 1.8L 4 cylinder car. They said that these small carbs really improved the fuel mileage of the I-6 engines, though they will decrease your performance if that means anything to you. I don't have any specs on the Mazda carbs, but maybe they chose simply a carb that fit the Ford bolt pattern. Good luck!

 

[Anonymous]

Not having to do with the subject, but if i add a hood scoop to the car and cut a hole on the hood to make it functional, would i be able to use a V8 open element air filter. How much would that improve as far as performance goes? Better breathing, colder air??? or should i just put the hood scoop and not make it functional?

What i have in mind is a car sort of like frdmustangcpe's 69 coupe except different color and mach 1 seats as far as appearance goes, the engine im looking for good gas mileage with some performance.

 

[Asa]

i see two seperate problems, one is with the hood scoop (and may not be a problem), the other is with the V8 open air element
with the hoodscoop, because of the offset of the I6 engines, i don't know how much it would help... it might not even make a difference where the hoodscoop is as long as it opens up under the hood near the carb/air filter
the prob with the V8 open air element is that the carb sizes are different, maybe if you put a 2bbl on your I6 you'd be able to, but i think you might have clearance issues with the valve-cover, i also don't know how much performance you are wanting from your six, so i don't know if you are looking for a 2bbl
check in the Parking Lot, and other engine pics, ask that member what they did
*looks through the shop pages*
i'm sorta suprised that no one has air cleaners... must not be enough demand... must be that everyone already has one

good luck
evan

 

[Anonymous]

What should the compressions psi be for a stock 250 cid (140-160 psi maybe? i have no clue at all) and what if the compressions are lower than what they should be. Does it mean i have to change piston rings or could there be something more expensive that needs to be changed? The car to which i am going to measure the compressions has been stored for like 2 years now, should that affect the compression readings or not?

 

[Anonymous]

So i guess 16-18 would be the middle ground for city driving. What's the best or top gas mileage i can hope for with the c4 and the 2.79:1 gears?(city driving)

 

[rbohm]

8) i cant tell you about a 250, yet, but my falcon, 170 3spd, 3.20 gear, gets 21-25 most of the time. the worst mileage i got was driving through kentucky pulling a trailer. that was 17-19 then. kentucky here is very hilly.

 

[CZLN6]

Howdy Tatao and All:

While a '69 coupe with a C4 and a 250 is cool, they are not known for being miserly. Another factor is that a '69 coupe is not exactly a light car. Factory MPG ratings are a very gross generality and, as '54ford and others have already said, the biggest variable is the driver.

To maximize MPG in a car like you've described (or any car, for that matter) you have to think about and maximize details. Best mileage comes when an engine and chassis are most efficient. Maintain as much heat as possible. A hot engine is more efficient. Avoid cold starts, warm up quickly, avoid choke conditions, minimize acceleration and accelerator pump uses. Have the idle set as low as possible and don't idle for more than 10 seconds. Coast when ever you can- avoid using the brake. Have it tuned to perfection. Use the maximum initial advance possible. have the hottest spark possible.

The stock '69 thermostatically controlled air cleaner system is a great one, both for mileage and for performance. I'd maintain it. You can add a K&N filter element if you like, but it will only matter at very high rpms or very dirty air. Neither of those are what you want for mileage.

Lighten the vehicle weight, maximize tire pressure, repack and set wheel bearings, make sure brakes are not dragging, and that the front end is aligned.

Finally, drive as if you have a raw egg between your foot and the gas pedal.

With an engine this old and having been in storage, I'd suggest using an engine flush oil flush on the 1st oil change. Commercial engine oil flushes are high detergent and will loosen and remove sludge and varnish to some extent. Then get it tune up and drive for at least 100 miles- more is better, before doing a compression test. The big criteria is evenness from cylinder to cylinder. I would not worry about cylinder pressures as low as 100 psi, as long as they are all about the same. That would indicate a well worn engine with no major problems- a good candidate for a rebuild, but not necessarily an emergency. If one or two cylinders are significantly lower than the others, that might indicate a more immediate problem, such as a broken valve, broken ring or ?.

Tuned AND driven to the extreme (as opposed to normal driving), in ideal circumstances, I believe that this vehicle could get 25 mpg or better in city driving. Why don't you do it and let us know.

Adios, David