FYI only. Wife & I drove Seattle to Bend, Oregon, 900 miles for this trip. Best gas mileage through the rolling hills of central Oregon was 19.5 mpg at about 60 mph, plus or minus. Usual average was around 19 mpg for most of the trip. 65 mph cruise. The Dart is a 1975 SE 4-door, 225-6 & 1945 carb, 904 trans, 7.25 rear. timing set to 5 BTC. 195-75-14 tires. Outside air temps about 50*, altitude averaged about 2000 msl. Past experience is that if we cruise at 70-72 mph, the mpg goes down by about 1/2 mpg. (Car has 268,000 miles on original engine and trans.) P

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Cool. Glad to hear about a Dart still out cruising the highways.

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Casually looking for a Clifford hyperpak intake for cheap.

Keep us posted, I want to know how its doing when its broken in

Do you know what the axle ratio is ?

Stock rear end, so I think 7.25. P

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

OOPs . The correct answer is "I don't know." (sorry Red Green.) Maybe some one in this group has the info? P

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

In the beginning of the end of optional ratios (1975-1976), Autos only got 2.76's especially in luxo barge A-bodies like the SE and Brougham...It would probably perform a little better all around if someone swapped in a set of 2.94's after the fact.

I would have expected better mileage from any rebuild unless the cam was not degreed (typically my aunt's 1974 Valiant 4 door going to bend for vacation 225/A904 packed for camping, typically got about 22-23 mpg average along the whole 1 week stay back in the 80's...comparatively my Dad's Feather Duster would average 29-30 on the way up if he didn't gun it going over the pass, and about 34-36 on the MOD run back down the pass). Are you just running 5BTDC just because, or have you tried 8 BTDC and set it back because it rattled? If using the stock 1975 distributor, go for 8BTDC, they are the last of the long slot lazy curve EI distrbutors and need a lot of help (is it a 375082, by chance?)
Did you change the jet size in your carb?

-D.Idiot

Sorry D.I., It's been pretty late in the day when I posted, and I didn't dig into my records when I answered. The rear end is a 7.25 with a 2.76 tag on it. Yeh, The sticker says timing "0" BTC, but I set it at 5*BTC just because. Distributor p/n is 3874082 and vacuum advance is 3755036. What speed did your Auntie drive at to get 22-23? Except for this Dart set at 5 BTC, all my others were always set at the fender sticker setting, and between Seattle and Helena Montana the best any of them got was 21 mpg at 70-75 mph. (same engines, trans, rear ends.) However, in ALL of them the speedometers read wrong, off by 2-6 mph at 70. I don't know how accurate the odometers were, or if it matters. (I have gone in to the speedo and adjusted the hairspring somewhat. Tried other speedo gears, but the one in there is closest.) Carb has the original jet. Tim- I think it's broken in. Does that happen before 268,000 miles?

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Back in those days 55 was the speed limit, and typically my aunt would speed up to 60 mph to make the upslope, and crest the hill/flat at about 45 mph. In the same trip, my grandfather's Chrysler 300 383-4v got around 13 mpg...a few years later he did some supertuning and used a holley instead of the stock carter and squeeked another 1.5 mpg out of it...I think if the internet had been available with the large knowledge of techniques he might have gotten more (of course hauling 6 people up and down fire roads all day checking out hiking trails and old volcanoes doesn't exactly make for the most efficient drive 5 days out of the 7 day trip).

You might bump it up to 8BTDC and see if you get a slight improvement, 3874082 is a 15L long slot with lazy smog springs, has a similar 8.5x vacuum can like the 1973-1974 cars... much room for improvement and performance there.

Thanks D.I. I've seen a lot of discussion here about distributor mods & vacuum advance, so I will be looking at that. Thinking back to the Good Ol Days- My (high school) old pink 58 Cadillac got 16 mpg at 75 mph, same as our 63 Chevy. But my dad's 68 Imperial with a 440 got 18 mpg- don't know what transmission. (Honeymoon car was and old 58 Buick Limited, struggled to get 11 mpg at 85 mph cruise! 19 1/2 feet and 5000 lbs of rolling American STEEL.) Those cars are now American Automotive Art Deco in museums- where we can share the memories. P

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

The last of the big imperials got the 440 and the A-727 transmission (no other choices available on the top shelf Chrysler, unlike the Newport or mid-60's 300's).

Another item that dawned on me was you exhaust...is it still the stock 1975 pipe? If so stock cat is shot and prone to getting restricted, removing that would help...if not a stickler for being original upgrading to the 2 1/4" pipe like the Dart Lite/Feather Duster should give a 0.5-1.5 mpg increase over the life of the car, depending on tuning (and a little more seat of the pants power)...that would put it at 20 mpg min, and 21mpg which would be about right on average for your options.

2 cents

-D.Idiot

My old '72 Duster got 22-27 with an economaster carb and an MSD. No other mods. That was a great car. I think it was called a Gold Duster. Wish I had it back.

Sam

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I agree with DI. He has the best knowledge on distributor tuning and between him and Doc they have helped me tune my long slot distributor (15R governor) and VC 208, 11X vacuum advance can to average between 22.2 and 22.5 all winter long here along the foothills of the Cascades. That's basically short 4 mile hops to the grocery store and to Bellevue and back (64 miles). When I do take it on a trips over the mountain passes it jumps up to 24.5 to 25 mpg if I don't push it too much over 75 mph.

As you can see if (click on the red link) I run a 8 3/4 Sure-Grip rear end, 2.5" exhaust pipe and a super quiet system. Free flowing exhaust helps a lot especially going over the passes. The temps stay down and the torque up....If I keep it above 2000 rpms on the steepest grades I have it made. Lots of power between 2000 and 2500 rpm!

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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

I haven't checked my records on it, but the exhaust may be the next place to attack. I can't say fer sure when/if the catastrophic converter was last changed, so I need to address that. I have been reeally good about changing the air filter regularly. I know there is a long thread on tweeking the distributor, but I've been slow to approach that issue, other then to make sure it is in fairly good condition, plugs, wires, cap, rotor & timing all fresh. Carb is running as well as any of our other /6's around town, cold and warmed up. I'm still not sure about the accuracy of the odometer. When we got the car, basically un-touched since new, the speedy-o-meter read 6 mph higher then actual speed. I tried other gears, and went back to the original, and just changed the tension on the hairspring to get only a 3 mph error. I would hope that I'm actually getting better fuel mileage then it is showing, but I haven't allowed my brain to follow that thought process. Lately my job has taken all my time, so no car work until June. Thanks for your support Ted!

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

What speedo gear are you running?
and what size tires?

Stock is a 29 tooth with a 2.76 rear and P205/70R14's.
I run a 28 tooth with the P215/70R14's.

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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

I am also curious as well, hopefully you haven't decided to keep the stock 195/75/14's.