With careful tuning and making sure everything is working properly, you should expect 19-24mpg hwy with your 73, stock. Making sure the dist vacuum advance works and timing is correct can be worth a lot. Installing an O2 sensor and tuning A/F ratio is also a good thing to do. Lots of other things possible: tight or leaking valves, low compression, wrong cam timing...

Lou

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Home of Slant6-powered fun machines since 1988

The OSAC valve on that '73 is killing city fuel mileage. Bypass it!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Why type of carb do you have ? Probably a Holley 1945.

Give us some more specifics about your car, gearing, auto or manual. Waht is your timing set at? Checked your plugs lately? What do they look like?

I get over 20 MPG in my 74 Duster and it is way heavier than your Dart.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Doing that actually helped many driveability issues on my '74...



On another note,

Looks like there's a fair spread across the board on how it goes, the Feather Duster is the 'no brainer' with how it's set up(gotta love that lack of power due to tall gearing, but being able to run 58 degrees of total timing on the highway is insane)...I wanted to see if anyone else with an earlier car had come close, having lighter cars and had dialed this in with proper carburation and timing.

I'm starting a job that will take me on a 130 mile round trip everyday with two major hills and flat the rest of the way. I'll be looking at a second car as a back-up in case the hpak duster has a mechanical error, in this case I'll be pursuing the 'mileage' question over the 'more power' question...will let you know when I get the 'test buck' and make some changes.




Thanks guys.

-D.Idiot

The 1945 was first used in '74; the 1973s came with Holley 1920s.
'74 Duster weight is pretty comparable to '73 Swinger weight (the '73 might be a tetch heavier).

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

My '66 Dart four door (225, 904, no idea what rear gears, ps, pb, 1945 carb, 13 inch tires) will average 20-21 a tank. I've never had it on a long highway run to see what kind of mileage it would attain. Here in a month or two I will give it a try..........
Todd

My car is bone stock 73 Swinger. Automatic trans, I'm not sure which transmission, it is a 1 bbl 1920. I changed my plugs in October, but didn't do a complete tune up. Valves were also relashed. I get something like 13 city/ 16 highway.

What kind of sucks is that I'm a wood guy, not a car guy. One of the many things that I considered when buying my slant was that I'd heard it is fairly easy to work on and would be a good car to learn on, but I don't have many tools and basically have a manual and some basic understanding. Adjusting the timing and all that I'm sure is not too hard, but I'd really need somebody to walk me through it. I usually take my car to a mechanic, which sucks, because you really have to rely on somebody else, and I wouldn't know if they really screwed up or not anyway ( which coincidentally, anyone in SW Washington/Portland Oregon, stay away from Ron's Automotive ). The mechanic I currently use told me that hoping for 17mpg was really a stretch. I want to do a 2bbl swap and put in a new coil and do a really good tune up, but this is my daily driver and any mistakes means I don't make it to work.

Anybody know a good Mopar guy in Vancouver/Portland area? Preferably one who's taking on students....

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1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

When I get back to work, get my remodel in the bathroom done, and get Ceej's 4 barrel conversion done, I'll be up sometime in the near future (a few months) to help another board member out. Since I'm in Salem just off of I-5 and Hwy 22 in Salem, it'd be a straight shot for you down and a straight shot up...send me a PM later and we should look at what's going on unde there for sure...

-D.Idiot

Gotta disagree. I know it isn't a Slant 6, but my 2.2 Intercooled and Turbo'ed 5 speed LeBaron gets me a regular 30 mpg average. I drive something like 75% highway and 25% city (which helps my average), and my commute is a 30 mile one way trip on a hilly section of road. Best of all, I get about 200 hp out of it and have seen 32 mpg or better on long trips.

I think EFI is the way to go. May not be the only way, but it sure makes it easier to cover for a big spread of conditions (i.e. 14 psi and 20 # of vacuum).

I know it doesn't add much to the discussion, but just couldn't hold my tongue.

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'15 Chrysler 200S V6
'74 Duster 360, factory 4 speed car

We'll see on my 73 soon (I hope). My 03 Neon gets 34mpg, doesn't really count though does it?

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70 Dart, 360, 727