I've been reading these topics on this forum for about 3 years and I'm always impressed with the wealth of knowledge from it's members and Doug Dutra.
I've professionally built Off-Road racing motors, vw's, Scat v-4's to Nascar and Grand National. I'm a Mopar fanatic and absolutely love these cars. I currently own a 69 Dart GT with a 225, 3 speed auto. I've always owned 318-340-360 Darts, Demons and Dusters always set up for street/strip performance. My new Goal is to build this motor for EXTREME MPG's so we can have a daily driver Mopar instead of buying an econo box. With experience, I know I will spend less time asking people who are more experienced than me with these engines, rather than trying to R&D with my own formulas. My goal is to reach 35 MPG's....Right now some of you are probably lying on the floor laughing at me and wondering where I've been getting my drugs from. But, I know it can be done with a lot of creative measures and the right combination.

Right now I saw an old post of a member getting 39 MPG's and said it was 2-3 more than stock, so I'm assuming this was a mistake. I've seen some combinations that made really good power and still got 22-25 MPG's So I make this as a challenge to see what real MPG's this motor can get even if it's a little underpowered. I rather drive a fully restored underpowered Dart with 35 MPG's than a toyota corolla that gets around 38-40. Nothing against these cars, without the technology from these auto manufactures building this motor would not be possible. And it is truly amazing what kind of power a 1 liter Yamaha R1 motorcycle can make. I'm also a motorcycle junkie!!!
My plans so far are to blueprint the block to make sure all the cylinders are square with the crank, make sure crank is square with the block. Balance and shot peen crank and rods. Pistons, compression and cams I need advice. I would rather have a hydraulic than a solid cam. Seems milling head to get compression is a common procedure, but since I'm changing pistons maybe this is not necessity. I'm really disappointed in the cylinder head design on these motors. The squish area is an old technology and these motors would seem to benefit from a small squash "Wedge type" combustion area greatly. Does anybody make a head with newer "Closed combustion design" similar to a v-8 head. I've read Dutra's article on these heads and it seems only pistons and re-shaping the chamber are the only way to get this effect. This is to bad. Someone should experiment with welding up these combustion chambers and re-shaping into a "Wedge style" chamber. Unfortunately I do not have the resources that I once did nor the time to machine it but it would be a fun project. Also a clean up port from valve to carb would be needed and a Dutra dual exhaust. As many of you guys seem to have a problem with the small collecting area in the stock exhaust manifold. I've replaced the points with a Pertronix but many of you seem to like the factory electronic unit from Australia so I will need one of those. As for fuel the 1920 seems to be an excellent carb but I'm a little skeptical of a 30 year old design. It seems to only have a main jet and the only way to adjust the pilot is to modify the "Pilot chamber" As with all components you can make everything work, but is it really worth it with this carb? I'm planning on restricting flow to the motor by a restricter plate or even possibly a smaller carb like a Solex pict 34. I'm just used to being able to swap out pilots, mains and accelerator pump nozzles to dial it in.
The design of this intake doesn't seem to help with any type of turbulence to help atomize the fuel droplets so machining a defector plate under the carb also might help for more complete combustion. Also adding a GV overdrive system is a must. This car gets to 75 and it sounds as if were going to explode!! And to finish it of.......for the guys still laughing on the ground you are going to have to change your pants after this I'm going to install a HYDROGEN ON DEMAND device to help with the combustion. I know many people are skeptical on these devices but I feel once these HHO Generators are perfected more people will be using them on there cars in the future. It is a great technology, many patents are free to download and build. Many people are using them on YouTube right now with excellent results.
I'm most sure it would be beneficial for all slant/6 owners any type of technology that could come out of this. I hope I'll inspire Dutra to use his gifts to build a motor for MPG's has he seems to have the most resources available. Also, can members post engine/car set-up and MPG's to see where we are all at. This would be extremely cool to see what setups get what MPG's as this would be a good starting point.
I know that this is an extreme challenge, I would rather be building a 225 with the Aussie blower intake and an Kysler 6 speed, but with the sign of the times I think this will motivate people to take a second look at these cars if we can get a true 30 MPG's out of them.
I apologize for the long post!!

Can't help with your formula, but just popping on to say you are not the only one interested.

I've seen some postings in general on this topic and the consensus (don't remember any that had a MPG goal, but like the sound of 35) seemed to be lighten the car, super six set up and exhaust, max out the timing and tune, gearing etc. Hope to hear others chime in with actual results and engine/car mods that work. Going off a very faulty memory, but seems like most felt that the 25 range was doable, but beyond that ????

Would be great to get 30's on the highway though! Unfortunately I don't have the dosh for the overdrive nor the ability to do one anymore, but would be very interesting to see how far you could go without one.

Anyway, looking forward to your progress and other's responses. With the price of petrol I'd rather enjoy the car, get great mpg and drive it all the time than have to let it sit because it costs me $50 or more every time I want to take it out.

Cheers

_________________
From Mopars to classic Minis and back to Mopars in 19 years flat!

Will work for roast chicken crisps!!

If you already have a pertronix ignition, you really don't need another one......

Either change your ignition last (save some money) or if/when you have a failure.

You should look into recurving the ignition optimium results.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Since the automatic tends to lose a bit of power from slippage and conversion of power through the tranny... I would opt to get an A-833 overdrive tranny and go manual since the tranny is locked to the clutch in one foul swoop... if wanting the automatic and doing it on a budget, getting one of the late A904's with the lock up convertor would help mileage a bit at least in highway repsects...

Changing timing curve will be a must...

Also what is your driving terrain like... some of the guys posting from the 'flatlands' will get more consistent 'cruise' type economy, than those of us who have lots of hills and mountains to cross getting from one place to another...

good luck on your quest...

-D.Idiot

Right off the bat, I have to suggest you drop the idea of using a conventional carb, and go with a port-injected, sequential-fire EFI system. The design of the slant intake, (unequal-length runners), doesn't lend itself well to truely equal cylinder-to-cylinder fuel distribution. With an EFI, you'd have greater control over that, and could very well optimize your fine-tuning to achieve the goal.

I think you can do it, but it'll be a battle. You might want to think about a more modern four-banger, maybe turbocharged.

Roger

If it were me I'd build a long rod short piston 170 with long runner port EFI manifold to boost torque. I just bought off eBay some ex-NASCAR 6.200" connecting rods for $100 that are over 150 grams lighter than the stock 170 rods. A 1/2" shorter piston with narrower metric rings will take out more weight and reduce friction. The rod bearings are narrower and smaller in diameter and will also cut friction. The port EFI would allow much tighter fuel control and greatly reduce cylinder to cylinder distribution differences so it can be run well lean of lambda. It's been proven with piston engine aircraft that more manifold pressure with a weaker mixture is more economical. It really reduces pumping losses. If you want quench then have the head welded up and work with a machine shop to get the combustion chamber shape you want. If you get trick with the electronics and tuning you can run a high compression ratio with a fairly short duration cam. As Duster Idiot has pointed out previously the Feather Duster used a lot of EGR to permit more timing, and ward off detonation. I feel a better combustion chamber design with a little EGR and knock retard would be a better strategy.

I would put this engine in front of a 5-speed like the Toyota R154 and some 3.23 or 3.54 gears. You get a 10.5:1 low gear ratio for decent acceleration from a stop and an overall high gear of 2.43:1 for economy with 3.23s. 3.54s net 11.5:1 in 1st and 2.67 in 5th which would also work well.

Reducing the car's weight helps stop and go economy more than for steady cruising, but it also helps handling, acceleration and braking which make the car more fun. Aerodynamic mods like a front air dam and low rolling resistance will probably also be necessary to reliably get 30+ MPG. Also, if you insist on driving the car 75 MPH I think you'll have a very hard time pulling down 30 MPG.

One more thing. I would not go for turbocharging since reducing the compression ratio to accommodate boost will hurt economy. A friend's old Turbo I Dodge 2-door with an automatic was a slug off the line and got low 20s on the freeway. My stock '67 Valiant is about as economical.

_________________
Joshua

I owned a 69 Dart for years.....possibly the least aero car on the planet.

If you want mileage in the mid 20s you had best spend some time on decreasing drag.

I added a trunk spoiler off a Volare SW and a roof spoiler off a chevelle wagon to my Dart. It helps shape the air flowing off the car. Ignore the poles

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....

My Dacuda cuts the air pretty good.
It could still use a front air dam and possibly a "bellypan" to get it to slip thru the wind a little better.
DD

For quite a while I followed the blog of a guy who was modifying his 1.0 litre, 3 cylinder, 5 speed Geo Metro. He kept detailed records for years as he tweaked it again and again for optimum gas mileage.

IIRC, the best mods he made were aerodynamic mods, including covering the wheelwells, and even running special hubcaps. He also found a huge gain by disconnecting the alternator, and running on just battery power, then recharging the battery at night.

Average economy was 61 MPG.

http://www.metrompg.com

With something like 60% (I think) of your horsepower going to displace air at speed, I can't imagine a '69 being "clean" enough to push much better than 30 mpg. Remember, the Chargers got the "500" treatment (flush grill) to contend with that huge air dam that the inset grill created. Our 67-69 Darts have that same inset grill design.

-Mac

A really interesting read is "Super Duper Mileage Experiment" on www.moparts.com. My friend Dave has a '68 Cuda coupe with a 318 getting 29.5 MPG at 65 MPH.

He is using a TQ off a 400 motor. (850cfm)

Much easier to build a V-8 IMO.

_________________
'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

Both of our slanted cars currently get between 20-25mpg depending on how much our foot is in it. Both are 225's with 4bbl intakes and mild cams. The one in our valiant we plan on setting up a throttle body setup on it some day down the road which should improve mileage.

_________________
Linder Tech.com
Bubba's Trailer Park

Finally getting good MPG from my 2.2 caravan with 32/36 DFEV weber carburetor conversion. Appox 17MPG, now all I need is bit more tuning to get 19 city. I used to average 10-13MPG with junky holley and weber before I was told to use certain jets combinations.

Waiting for extra jets order so I can final re-tune. Oh yes, low bucks WBO2 controller came in yesterday! Google JAWS wideband O2.

Cheers, Wizard

30 is super from a Dart, in my opinion. Mine has gotten an average of 24 the past two tanks(Edelbrock 500)......but I have been driving very conservative-like. Not dangerous.....but easy. I would love to get 25 driving "normal". For what it's worth......I only get about 16-17 at 75 mph. Beside the fact that I'm turning 3100 rpm....I can start to feel the "wind-cutting" limitations of my old Dart.
It takes money.....but it can be less than a new Toyota for sure!
Good luck!

_________________
225 Cubic Inches of Iron-Head American Muscle

225 bored .040 /.100 off block, Schneider Cam 224@.050~ .480 lift - Stock valves, blended bowls, Offenhauser intake with 500 Edelbrock carb

My build was based on creating more torque and better mileage. I drive a minimum of 130 miles a day with my 74 Dart. A year and half ago I got a bad oil filter which collapsed and would not bypass and starved the engine of oil. It happened one morning on the way to work right after a oil change.

Thus the "torque and mileage" considerations during the rebuild. See the "engine build" section for the steps I have taken so far on the engine. As pointed out for good mileage there is more to consider than just the engine. Doug Dutra gave me a long list of things to do.

I am continuing to upgrade the car and fine tune the engine. So far I have gone from 18 mpg average to 22 mpg average. I do not drive gently, but rather aggressively and cruise well over 60 mph. My commute is mixed city stop and go, back roads and freeway. I have been able to hit 24.5 mpg on some commutes when it was very warm during the summer months.

I am continuing to collect and rebuild/modify various one barrel carburetors to fine tune the engine. I am very confident that I will hit consistent 25 mpg. If not with the one barrel, I will switch over to the 4 barrel Holley 390 and shoot for 28 mpg.

I have yet to find out what mileage the car will get on a trip. I am sure it will be much better than the commutes back and forth to work.
One observation after the rebuild, it has a lot of pep and is a lot more fun to drive

_________________
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

What brand oil filter collapsed on you Ted?

Fram?

_________________
'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick