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Feather Duster 30+ mpg, really?
https://slantsix.org/forum/viewtopic.php?t=26227		 Page 1 of 1
Author:  MichaelS [ Wed Dec 12, 2007 2:59 pm ]
Post subject:  Feather Duster 30+ mpg, really?
Dose anyone in here have a Feather Duster or Dart Light and did they really get near 36MPG. if so are they really slugs with tall gears or what did Mopar do to make those MPG's
Author:  DusterIdiot [ Wed Dec 12, 2007 3:29 pm ]
Post subject:  Yes...and no...
Quote:
Dose anyone in here have a Feather Duster or Dart Light and did they really get near 36MPG. if so are they really slugs with tall gears or what did Mopar do to make those MPG's
Several members here do have them, my parents had one new off the lot (became my daily commuter in High School), and I have one in modifed form...

The options changed over the 1976 production run...

Drive train options were:
225 slant six, Auto Tranny + 2.76 rear
225, Manual 3 spd + 2.94 rear gears (up to late 1975...these models came 9" drums...)
about late 1975, to the mandatory change over in 1-1-76 it became
225, A-833 Overdrive manual tranny, 2.94 rear gears

aluminum cast one peice one barrel intake manifold
Holley 1945 with 612 main jet and some changes to the calibrations
Fatter header pipe (2.25")
Pipe from the cat convertor (after the header pipe) was the same as the 318 (2.25" to muffler, then 1.875" out to turndown by bumper)

Distributor was curved so you installed it at 12BTDC, 18 degrees of mech advance, Vacc. advance added more advance (to the point it only went away after 5" HG)...

Use of a Vacc. switch and a fat EGR (model 4026261..only for the Feather Duster/Dart Lite) to knock back the ping (it didn't help on uphill climbs)

Gas filler tube restrictor so you can only fill the tank with 14 gallons instead of 16-18 (uses the same A-Body gas Tank like all other years before)

aluminum reinforcement under the trunk and deck lid (some models didn't get both lids this way...mix and match at the factory)... the bumper reinforcement beams were also aluminum... This sheds about 150 lbs off the car, but the car with mandatory crash and safety equipment gave the weight back (it's about 3000-3100 lbs with a full tank of gas)...

My parents got 30-32 on the flats of I-5, some people have reported 28-34 depending on the drive...

And yes, compared to a Chevette it was a slug... :roll:


-D.Idiot
Author:  lincparts [ Wed Dec 12, 2007 3:48 pm ]
Post subject:  great info
great info, i'm amazed at what slant's can do in terms of power,economy, and performance of both. I'm tring to pass the 20+ mpg mark in my 63 170/904 with super six. the super six with 2 1/4 exhaust helped 3 mpg(from 15-16 mpg to a good 19-20 mpg), and still tuning!
Author:  Charrlie_S [ Wed Dec 12, 2007 4:27 pm ]
Post subject: 
You should be able to get that car up to the upper 20 mpg range. MPG Fanatic is getting 26-28 mpg with his 64 Valiant 170 3 on the tree, and it runs 18's in the 1/4 mile, "granny" shifting. It is a fresh built motor.
Author:  MichaelS [ Thu Dec 13, 2007 9:41 am ]
Post subject: 
Great info, thanks. Got a good recipe for improving the mileage of my '74 225 auto Dart? Its a 4 door, I saw somewere in a magazine that 4 door Darts were lighter than 2 doors? Is this true?

This website is great, before pulling the old girl out of the barn I didn't know the slants had such a big following.
Author:  Dart270 [ Thu Dec 13, 2007 9:58 am ]
Post subject: 
Usually, the 4dr cars are about 20-30 lbs heavier than the 2dr post cars. The hardtops are a bit heavier than the post cars, I believe, and the converts are heavier still.

Lou
Author:  Rug_Trucker [ Thu Dec 13, 2007 5:07 pm ]
Post subject: 
My 198 got 25.4 on 93 octane with the 3 speed and 3:23 @ 65-70. Best of 29 @ 65 I had a spit exhaust with the mufflers and pipes I have on it now. It did have the cracked into 3 pieces factory exhaust manifold. :shock:


then I put the 2bbl and headers and never checked again at legal speed. I did average 22 @ 80-82mph
Author:  MichaelS [ Fri Dec 14, 2007 9:21 am ]
Post subject:  worst mileage
I am assuming the worst mpg Darts are the early emission equiped versions like mine, a '74. 20mpg highway was my best. 17mpg average.
Author:  DusterIdiot [ Fri Dec 14, 2007 9:08 pm ]
Post subject:  No not really...
Quote:
I am assuming the worst mpg Darts are the early emission equiped versions like mine, a '74. 20mpg highway was my best.
20 mpg isn't bad and about average for a heavy car with 2.76 rear gears... manual tranny would give back some mileage, better timing helps... but the weight is also kind of restrictive (20 wouldn't be bad either for a slant six powered B-body...)

I used to get 19-20 from my 74 duster with 3 spd on the floor and 3.21's, Feather Duster exhaust upped that to 20-21, no change in mileage with highway gearing, but the clutch burning and motivation time changed.

-D.Idiot
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