Gas milage build? Or other ways of improving?

[Axels73Charger]

Ok so i've been all "im gunna get a SB so i can get better gas milage than" and "I kinda want to swap a SB for a BB" OK well I'm just trying to make it easier on me. I've been trying to find a 73/74 Charger thats near me. So I can figure out how much money im gunna need for buying a car close to me... Its a pain in the arse but oh well. I've found one thats about 2 or so hours from me. Now im not saying this is the one but its a BB 400. Again that made me start thinking. Its cheaper (2000) its got a 400. Its a SE with no opera windows, and its ready for me to make it into a burn notice clone. In easy terms. I can make the rear windows roll down. I figure 3000 will be what I need for interior ect... Thats probably low but Im just trying to think out loud here.
Now for the important stuff. The reason im posting this. Besides telling storys What could I do to make a mild 400 get high teens in gasmilage? Is there anything I could do for a build or what ever?

[Charger´69]

What could I do to make a mild 400 get high teens in gasmilage? Is there anything I could do for a build or what ever?

Rearend something 2.XX and/or overdrive transmission and of course you could assemble injection to it´s engine. There is nowadays easy almost "bolt on" injections available, like EZ EFi fuel injection etc. 

... And light right foot helps much also 

[Axels73Charger]

Cool. Read some where headers and carb help. Then something about tuning and then something about exhaust... Yeah after the 3rd or 4th article/thread/post I was confused and I had a head ach. But did I miss anything?

[Charger´69]

Cool. Read some where headers and carb help. Then something about tuning and then something about exhaust... Yeah after the 3rd or 4th article/thread/post I was confused and I had a head ach. But did I miss anything?

I think you can get to those mpg that you wanted to only with tuning engine properly etc. and easy driving, but if you want very high mpg maybe you should think injected engine and overdrive transmission  I know that those aren´t the cheapest ways to do it but maybe best way to do if you want to improve mpg to highest possible with 400cid big block..

[Axels73Charger]

Ohok i'll look into fuel injection... So... better exhaust isnt gunna help? I was thinking dual flowmasters...

[Charger´69]

Ohok i'll look into fuel injection... So... better exhaust isnt gunna help? I was thinking dual flowmasters...

Everything helps that makes your engine´s efficiency better 

So better exhaust helps, carb that is just right to your engine helps and tuning everything properly helps 

Injected engine is just one way to do it, something like this: http://www.spiderautomotive.com/edelbrock35090.html

Think how much you want to spend money when your goal is to get high mpg. If you want to spend something like $4000-$6000 money you´ll get good injection system and overdrive transmission but with that money you´ll drive pretty long time with 3-gears transmission and carburtated engine, it´s your choice 

[Axels73Charger]

.... haha its gunna cost more then the car... Good thing im getting a neon too. Well if i can get 15 or so mpg i think i'll be ok. I might get more idk. I know some one (my driving instructor) who owned a 73 340 that got 25 mpg highway on low rpms... Any other way to do that with a 400? Or how much could i get if i put the 400ci engine up for sale?

[Charger´69]

.... haha its gunna cost more then the car... Good thing im getting a neon too. Well if i can get 15 or so mpg i think i'll be ok. I might get more idk. I know some one (my driving instructor) who owned a 73 340 that got 25 mpg highway on low rpms... Any other way to do that with a 400? Or how much could i get if i put the 400ci engine up for sale?

I don´t think that is possible with 400cid, maybe with overdrive transmission and EFi but  Or then tune everything properly and drive 40mph on low rpms 

Maybe 17-18 mpg max and even then you´ll have to have everything in good condition and properly tuned up  And LIGHT foot 

[chargd72]

Think how much you want to spend money when your goal is to get high mpg. If you want to spend something like $4000-$6000 money you´ll get good injection system and overdrive transmission but with that money you´ll drive pretty long time with 3-gears transmission and carburtated engine, it´s your choice 

If you spend $5000 getting OD and EFI, how long would it take until you saw any kind of return?

Let's say your stock 400 gets 10 mpg, and now 5 more mpg with the upgrades.  Driving 5 more miles at the rate of saving $2.50 per gallon you would have to drive over 30,000 miles until you'vd paid off your investment and started saving money.    

Are you looking to save money right away or later down the road?

[tricky lugnuts]

Check out the MPG thread people have been doing.

I'm running an original, stock 1971 440 - never rebuilt - and I'm consistently getting 17-18 mpg on the highway with a stock-style 625 CFM carb, 3.23 gears, tall tires and a 727 transmission.

Mid to high teens shouldn't be that tough with a stock build, properly tuned . . .

Of course an OD trans would help on the highway mileage and your gearing will have a lot to do with efficiency at highway speeds.

One thing to remember is that it's always going to suck gas driving in town with a lot of idle time. My factory manual says my 440 will burn through a quarter gallon of gas every 10 minutes at idle. So every minute your engine is running and you're not moving your mileage is going to suffer...

Another thing to consider is the small block to big block aspect. I was running a fresh 340 before the 440 and only getting about 15 mpg on the highway. The 440 seems to do better in terms of mpg, maybe because it doesn't have to work as hard to get the heavy old Charger moving, and maybe because the engine is more worn in with less friction.  

[Charger´69]

Think how much you want to spend money when your goal is to get high mpg. If you want to spend something like $4000-$6000 money you´ll get good injection system and overdrive transmission but with that money you´ll drive pretty long time with 3-gears transmission and carburtated engine, it´s your choice  

If you spend $5000 getting OD and EFI, how long would it take until you saw any kind of return?

Let's say your stock 400 gets 10 mpg, and now 5 more mpg with the upgrades.  Driving 5 more miles at the rate of saving $2.50 per gallon you would have to drive over 30,000 miles until you'vd paid off your investment and started saving money.    

Are you looking to save money right away or later down the road?

That is just I mented too, before you can save any money you´ll have to spend big amount of it to get high mpgs, is it worth it? That is question what should be thinked..  

Maybe if you drive thousands mails in year maybe then it is reasonable, but like I drive maybe 2000-4000 miles in year with my Charger I wouldn´t go injected engine just to save money.. It would take years to get those money back   Maybe overdrive transmission is something I would think about, but this 3 gears TF727 is so simple transmission that I won´t change it to anything  

[1BAD68]

If you keep it tuned up, put 2:73 gears in it and stay out of the secondaries, you should get decent mileage.

[Charger´69]

By the way, my previous car was supercharged and injected Camaro (350cid+Paxton+Megasquirt) and with that I got 21mpg in highway driving +70mph and normally in town it did go 9mpg. So injection helps much, but is expensive if you buy ready bolt-on setup  My Camaro had DIY Megasquirt etc. but still intake manifolds and throttle bodys and injectors cost big amount of money  And it had also 4-speed overdrive half automatic transmission, it was also fun to drive and kind of fast but I´m glad that I have now real old school Charger without any computers   

[Wicked72]

yes fuel injection will make a huge diff. try http://www.professional-products.com/ a good price and extremely easy to install. after that, you get an OD trans and diff rear gears and your golden.

[elacruze]

MPG is simple, keep everything high.

Vacuum, compression, fuel/air ratio, gear ratio, and especially the right foot!


On cars like ours, fuel mileage is largely academic. I can find a 5 year old Cavalier on every corner for $2500 that gets 30mpg all the time.

[chargerjy9]

my 73 has exactly that set up, stock 400 4bbl with 2.73 gears,
I am fairly light on the foot, tho I do get into it once and a while, the engine was dyno tuned. it is set up optimally. I get 10 mpg around town and just less than 13 Hiway at 65 -70 mph

[elacruze]

my 73 has exactly that set up, stock 400 4bbl with 2.73 gears,
I am fairly light on the foot, tho I do get into it once and a while, the engine was dyno tuned. it is set up optimally. I get 10 mpg around town and just less than 13 Hiway at 65 -70 mph

There are cases where having the motor run faster gets better mileage. Remember that the factory was restricted to certain criteria in both emissions an speed. I had an '86 Camaro with 305 4bbl, 700r4 overdrive automatic and IIRC 3.23 gears. It usually got about 24 on the hiway, running between 55-65mph. I once ran it from Ft. Wayne Indiana to Detroit, got a little crazy in the head and held an average speed of 88mph. The stupid thing got 27mpg on that trip. Go figure.   The motor was just a lot more efficient at higher RPMs.

[Charger´69]

my 73 has exactly that set up, stock 400 4bbl with 2.73 gears,
I am fairly light on the foot, tho I do get into it once and a while, the engine was dyno tuned. it is set up optimally. I get 10 mpg around town and just less than 13 Hiway at 65 -70 mph

There are cases where having the motor run faster gets better mileage. Remember that the factory was restricted to certain criteria in both emissions an speed. I had an '86 Camaro with 305 4bbl, 700r4 overdrive automatic and IIRC 3.23 gears. It usually got about 24 on the hiway, running between 55-65mph. I once ran it from Ft. Wayne Indiana to Detroit, got a little crazy in the head and held an average speed of 88mph. The stupid thing got 27mpg on that trip. Go figure.   The motor was just a lot more efficient at higher RPMs.

OT, but I had same year Camaro before, it was Iroc-Z and it was Supercharged and with Megasquirt  I had also 3.23 gears and normal in highway was 21-22 mpg 

[HPP]

 The reason for that is becase at 88 mph, you were closer to the torque peak and using that power more efficiently.

Fact; an engines volumetric efficiency peak coincides with its torque peak.

So, the simple exercise is to build an engine with cam and compresion specs to achieve as low and broad of a torque curve as possible. Match the trans, rear gears, tire diameter, and chosen cruising speed to match that torque peak and your golden. No overdrives, no efi, nothing complex, nothing more expensive than a regular rebuild. A simple build with a fair amount of forethought is all that required.

Other factors that will help the engine reach efficiency levels comparable to new cars are headers, smaller cams, smaller carbs, ignition timing that is dialed in to a gnats ass worth of perfect, and a consitent, reliable, hot spark.

Example of this; the 440 in my 3/4 ton truck runs a 727 trans, 4:10 rear, with 33" tires. At 80 mph and 3200 rpm, it is getting 18 mpg. It runs a small summit cam, a 625 carter, headers, and 10:1 compresion. Nothing trick about it. But, its torque peak is also 3200 rpm and I spent a fair amount of time getting the ignition curved dialed in. Put that same combo in a car that weighs a 1000# less, and it could probably break in to the 20s. All without efi or overdrive.  

[Todd Wilson]

Throw the 400 into a deep lake!


Todd

[Charger74]

Throw the 400 into a deep lake!


Todd

Kind of have to agree with you Todd.   

Heck, if your really care about mileage, why not go with a 318/2bbl/2.73 gears and overdrive.   My 73 used to get awesome gas mileage with that setup minus the overdrive.  I could fill up, drive about 80 miles to Tucson and my gage barely moved until just outside of Tucson.

[Axels73Charger]

No Its was just kind of a thought. See Im trying to get a 73 318 and but a 360 in it. But I say some 400's and a 440 that went for cheap so I was thinking "Thats why my parents are buying me a neon..." So I mean... The Charger will be my nice days driver. So summer daily driver. But having a 440 would be cool. But I mean besides that I was just trying to figure it all out coz I do have to pay for the gas... Its almost 4 buck I think...