MPG The Best Of Both Worlds

[skep419]

Car-1969 DART GT
Weight-3300
Gear ratio-3.91
Tire diameter-245/60/15
Engine CID-365
Head Type-EDELBROCK
Valve size-2.02 1.60
Head Work- MILD PORT
Cam- Comp Cams 20-225-4
284 int./296 exh.Carb type and size-HOLLEY 4150HP DP
Jet sizes-74-78
Plug number and brand
Intake Manifold Type-RPM AIR GAP
Piston Make-SPEED PRO 4 VALVE RELIEF
Compression Ratio-9-1

Trans type-727
Trans Mods-MANUAL VALVE BODY
Convertor type-MIDWEST CONVERTER
Convertor stall-2800
Trans Brake-no

Drive shaft stock or aftermarket-STOCK

Initial timing-17
Total timing-35
Total advance at what RPM-2000

Rear end type-8 3/4 3.91 suregrip, single spline side gears, yukon axles,green bearings.



What would be the best mods to up the MPG?

 

[abodyjoe]

tighter converter and over drive.

 

[skep419]

Car-1969 DART GT
Weight-3300
Gear ratio-3.91
Tire diameter-245/60/15
Engine CID-365
Head Type-EDELBROCK
Valve size-2.02 1.60
Head Work- MILD PORT
Cam- Comp Cams 20-225-4
284 int./296 exh.Carb type and size-HOLLEY 4150HP DP
Jet sizes-74-78
Plug number and brand
Intake Manifold Type-RPM AIR GAP
Piston Make-SPEED PRO 4 VALVE RELIEF
Compression Ratio-9-1

Trans type-727
Trans Mods-MANUAL VALVE BODY
Convertor type-MIDWEST CONVERTER
Convertor stall-2800
Trans Brake-no

Drive shaft stock or aftermarket-STOCK

Initial timing-17
Total timing-35
Total advance at what RPM-2000

Rear end type-8 3/4 3.91 suregrip, single spline side gears, yukon axles,green bearings.



What would be the best mods to up the MPG without sacrificing E/T to much.
Here is what I have.
Sell 360...400 big block that needs a rebuild in the garage ( more power at less rpm)

Edelbrock 750 vac sec carb. 3.23 gears (came stock with suregrip)

I have an appointment to get the Dart dyno tuned June 4. Want to get the best tune possible.

Swap carb and gears, buy a new cam?
Keep carb, cam, swap gears
Keep everything the same, tune

 

[furz4]

What kind of MPG are you getting now? How much highway driving? Off hand I would think a smaller cam to build more low end cylinder pressure and a higher rear gear or some kind of overdrive.

 

[375inStroke]

Are you kidding? I don't think that carb ever took MPG into consideration when it was designed. 3.91 gears has got to kill any kind of mileage. That cam, too. Perhaps the converter isn't that big of a hit in the MPG department. Many of the things the manufacturers do only increase MPG a tiny bit, but added all together, they get them where they want. These are the three things that would get the best mileage increase, I think. At 9:1 with aluminum heads, you could go higher, but that's more difficult to do than the other changes. Lower weight always helps everything. Better MPG, acceleration, braking, and cornering. Did you put this car together the way you wanted it, but can't afford to drive it because of the gas, so what's the point in having it if you can't drive it? My stock '69 Charger R/T, with 100,000 miles on it, gets 9MPG. Both of my 273 Darts, a '64, and a '69, both get around 15, and a '69 225 I had was around 18MPG. I knew someone that got 30MPG in his slant 6 Barracuda. I'm thinking that worn out motors use more gas. See if you can get a wide band O² sensor to observe your air/fuel ratio. This will help you dial the carb in so you're not just wasting gas when cruising. You'll need to install a bung in the exhaust close to the motor. I guess you can get by with just one if the motor is balanced side to side, or install two bungs, and switch the sensor from side to side to compare. The wide band sensors are around $100 to $200, I think, plus you need the meter to read them. Any of this sound like something you want to do?

 

[375inStroke]

Isn't the tighter converter and lower RPMs with that cam going to really bog the motor down, causing a lot of wasted fuel to go out the tail pipe?

 

[skep419]

Thought it would be fun to hear what other gear heads would do.
Also I thought it would be cool to swap some stuff on the dyno (750 ede vs, 750holley dp).

 

[ramcharger]

Smaller valves, magnum heads, smaller cam, tighter convertor, taller gears, and a VS type carb.

 

[forphorty]

Keep in mind that if changing some of the major components, depending on how much you drive, you may never recoup your investment in fuel savings. Also, how much slower are you willing to make your car?

 

[Purple Haze]

Put in a 225, 2.26:1 gears and stock 904, that should do it. Then when you want go put back all that's in it now.

 

[inkjunkie]

it will take a long time to recoup the money it will take to get good fuel mileage with it. i would start by dumping the dinosaur of a carb and going with efi of some sorts. an od trans with a lock up convertor this way you do not have to sacrifice the stall would be next up.......how much $$$ do you want to spend?

 

[SirDan]

id go with a 5 speed with a nice 5th gear overdrive. then you could at least short shift it and keep the rpms low which i think would save a considerable amount of gas. maybe go with some kind of efi if you can. but any 5 speed for an a body will be a pain and cost i lot id assume. i was talking to the keisler guys at carlisle and they were telling me their 5 speed wont fit in the transmission tunnel of the dart, id imagine there are lots of other issues but im sure those are covered in another topic.

Whats your mpg now out of curiosity?

 

[rumblefish360]

Get an overdrive tranny and drop the cam size down.

In reality, you can't have both unless you upgrade to something like what the Corvettes have/are doing. Adding a super charger/ turbo is the best bet for power on top of the engine with mild work.

 

[skep419]

Not sure if my speedo gear missing a couple teeth has anything to do with it but 96 miles to 18 gal average. With a couple of these...
[ame="http://www.youtube.com/watch?v=ZIt2L6Js0Cs"]YouTube- 1969 Dodge Dart GT Burnout[/ame]

 

[tyler_s18]

overdrive will help a lot. i think you could do a full t5 5 speed manual trans swap fr about 2000. so probably carb and cam and tune it then see about od. my boss has 3.23 gears in his big block car and gets good enough mileage to daily drive it. if you really wanna drive it go pick up like an 8 1/4 rear with the 2. something ratio and that will get more mileage i think lol. but there are a lotta cons to the weaker rear end

 

[skep419]

Get an overdrive tranny and drop the cam size down.

In reality, you can't have both unless you upgrade to something like what the Corvettes have/are doing. Adding a super charger/ turbo is the best bet for power on top of the engine with mild work.

Turbo puts more air to the engine which requires more fuel right? Or does it make more power at less rpm's so it saves on fuel?

 

[Longgone]

To get a little better mileage on the cheap I would install a set of 3.23 gears in the rear and buy a vacuum gauge. Drive with one eye on the rode and the other on the vacuum gauge.

 

[goldfish65]

My $.02, when you look at the bottom line, better to just drive the car the way it is and enjoy it.

 

[1968FormulaS340]

$500 Honda Civic as a daily driver.

 

[mopardude318]

$500 Honda Civic as a daily driver.

I just bought a 500 dollar 93 toyota celica today!!! I'll start my own thread.

 

[Backtobasics]

Gear it down to 3.23
Converter replaced to something closer to stock, maybe 2200 unit, somewhere in there.

Vacuum gauge
Carb jetting


What are driving patterns? Better MPG on highway or around town jaunts?

 

[HotLines]

If you're gonna run 3:23 gears, you're gonna need a 700R4 because the 518 ain't gonna give you any low end get up and go

 

[rumblefish360]

Turbo puts more air to the engine which requires more fuel right? Or does it make more power at less rpm's so it saves on fuel?

When the engine is under boost, it will require more fuel. However, when at cruise, it will require less fuel since boost is low or not there.

Alotta guys and gals love waving the flag of "I do it without boost" and I as well love to say I can make some decent power without it. While all that is great because you built it or what ever, boost on the engine makes alotta power and if done right, it really makes alotta power without costing a grooosss amount of extra fuel.

You can have a mild engine, cam, compresion set up and then add boost on top when needed for a whoopin amount of more of power. It's just not cheap to add it on. But well worth it in terms of power.

Here you'll use the torque to your advantage. Cruise in and around peak torque to take advantage of the most and best power making abilty of the engine when it's converting liquid gas into power for cruising in the car.

When the need to go fast comes, the boost poors in and off you'll go.

Now a melloer engine can use a lower gear set and a overdrive tranny to it's best advantage. The boost will cover the rest.

 

[moper]

I'd run the vacuum advance on the ignition and use something like the Street Avenger 670 vacuum secondary. That cam is not a low rpm deal, and the engine has low static ratio so it's not going to be snappy. I dont think simply lowering rpms will help. You need to keep the engine in it's rpm range but give it as much advance as you can (I'd wager you could re-time to 20° initial and 38° with no problems at all). With the loose convertor and gear I dont think you need that second accelerator pump or larger power valve restrictions that the DP carbs have.

 

[inkjunkie]

leave the car alone and get a