Well, I have my motor mounts and new U-joints ordered. After that project my next step will be to start tuning the engine a little. My ultimate goal is fuel mileage, if I increace HP and torque along the way great, but not my primary goal. Think it would be cool to have a classic Mopar that got between 25-30 mpg. My question to all you Guru's is if you wanted to squeeze every mpg you could out of a 225 dart, how would you set it up?

Not real experienced with slant six in particular, but have been doing engines for a long time and I believe the basic principles are the same. If you build efficiency, you get both improved mileage and power.

If you compare todays engines to yesterdays engines, they are getting a ton more power AND fuel mileage per CID. My 2012 Fusion with a FI V-6 has no problem blowing away my co-worker's 70s carbed V-8 tanks. Copy the improvements to modern engines more closely and you will get what you are looking for.

Most stock automotive engines, especially as you go further into the past, have poor casting and machining quality in the heads. Porting will gain you both mileage AND performance. Reducing friction in the engine will also help in both cases- roller rockers, electric fuel pump, electric fan and a larger alternator pulley will all reduce pulling friction on the engine.

it also helps to think of your engine as an air pump. The more efficeintly you pump air through it, the better it works. An efficient cam, helping the heads breath through porting, reduciing friction within the engine, less exhaust back pressure and a well-tuned two barrel carb with smaller primaries with larger secondaries will help both gas mileage and power. Better yet, a tuned electronic fuel injection system or a turbo charger if you have the coin to afford them.

Also, don't forget that the air-fuel mixture must also be ignited efficiently, so a high quality spark system will be beneficial, high power coil, the best spark plugs, better wires, cap and rotor. Find and install an electronic ignition if it does not have one.

Finally, it comes down to gearing. "Highway" gears ( in the 2s)will improve your gas mileage, while "pulling" gears ( in the 3s and 4s) will give you more take-off power but requires the engine to run at higher RPM during cruising, using more gas. Finding a good balance will help your cause.

Mr. Zeal made some good points.
The Slant was never known as a engine that gave good/great fuel economy. Most well tuned will be able to pull 20 mpg. There are many factors that will improve that number as well as reduce it. One is where you live and the geographics. Hills/mountains,flatlands and road speeds would determine the most fuel efficent choice of gear ratio.Same with overdrive, and locking converters for automatics. For me most roads are open highways with speed limits of 75 miles per hour. A 2.76 rear with a 26'' rear tire will have your rpm's about 2200@65 mph .Also older cars as the Dart/Valiant aren't the most areodynamic compaired to todays.

GAranger1403,

I agree, who cares about HP, I just want more torque! to move the brick efficiently.

Since I have set out to do just that about 12 years ago......here goes.......I do drive over 120 miles a day and track the mileage like a hawk!

1. I do run 26" tall tires, "Toyo Eclipse".
2. I do have a 2.76 ratio 8 3/4 rear end.
3. I do run a 2.5" exhaust system which is ultra quiet, (vacuum goes way up under load).
4. I do run a front air dam to reduce turbulation and direct more air into the radiator.
5. I did tip the nose down a little per Doc's suggestion since my 74 Swinger is basically a brick, 2" difference.
6. I did deck the block to increase compression to 9.5, again per Doc's recommendation, huge change in torque output and better mileage.
7. I did throw all my tools, etc out of the trunk to lighten it up, 300 lbs lighter.
8. I do drive by my vacuum gauge and tach, per Doc's recommendation.
9. I do run alcohol/water injection to help mileage, more punch going over the mountain passes.
10. I did convert to a high energy electronic ignition
11. I do run cold ram air
12. I did convert to electric fans which gives you and easy 2 mpg, faster warmups and less drag on the motor and reduces heat soak for immediate hot starts.
13. I did run SL6 Dan's fuel line mod for less percolation and fuel loss.
14. I do run a heat deflector under the carb, reduces heat soak.
15. I did do the distributor recurve for a full 60 degrees of advance at cruise.
16. I did switch to synthetic oil for more protection and less friction losses.

The list goes on....

You can click on the red link below my name to view pictures and the changes over time...

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

My personal opinion: The best bang for the buck, is to increase the compression ratio. Depending on other factors, a minimum of 9.0-1 to a max of 10-1. There is no down side to doing this. It helps both power and economy.

_________________
Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Thanks for the inf guys. Wow Ted, that's what I'm talking about, lots of good inf. there! I see that you live in Washington and do alot of driving at elevation. I live in south Georgia where the tallest thing I drive over some days is the speed bumps in Walmart's parking lot. I see in your sig line that you can get 25+ mpg. I figure with roughly the same set up I should be able to squeeze out 27mpg or more on flat Georgia/Florida roads. Sounds good on paper.........errr.....monitor anyway.

Thanks again guys!