any body building a mopar for max mpg?

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tobysoldblue

tobysoldblue
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I know we all love performance,but is anyone on here building,or have built a old mopar for maximum gas milage?Im sure a slant six,or stock 318 would be the best,with a 2.76 gearset.What i want to know is,whats the rest of your combo?If running a slant,is there a od auto that bolts up?Or is the od 4 gear the only option for extra milage?On 318,is there a 4 barrel carb thats better for gas milage than the factory 2 barrel?I noticed my old thermoquad had smaller primaries than the original 2 barrel i took off the 318.Is there a way to keep the secondaries from opening,incase my foot gets heavy?lol
 
any 4 bbl uses less gas then a 2 bbl.when your foor isnt in it,,,lol
the thermo quad is a great carb,,small primaries,, very large secondarys, but to big of a carb cfm wise for most stock or mild 318,s..i use a 500 cfm carter/edelbrock AFB carb on a 241 C.I. dodge red ram motor in my street rod,, 323 gears,, 18 mpg at 80 mph with the a/c on,,
 
If memory serves me......Back in the day.....used to remove a piece of linkage from the TQ that kept the secondaries from opening. Stored it in the glove box until it was needed for a street race or whatnot. :wink:

It was a very early form of gas conservation, but it worked....lol
 
I like Holley vacuum secondaries for that reason. You can easily put in a stronger spring in the vacuum can to delay the secondaries from opening.
 
The secondaries on the TQ are spring loaded and adjustable. If you don't want them to open, or open much later than normal, just increase the spring tension
 
If /6 is the direction, www.slant.org is the place to be. There are some over there that are truly focused on MPG, and many are well into the 30's in highway mpg. It appears there is a lot to do to the distributor, and carb. They have the lash adjustment down to a science.
 
not to steal this tread but im thinking about a 3.9,maybe in my street rod just to be different,,
 
The 3.9L in my Dakota was a slow pig and terrible on gas. My Hemi Ram gets the same milage.
 
The last Dak I owned was an 93. It was a V6 xcab long bed SLT and @ 161000 miles still got 21.1 on the highway
 
I don't know about building a mopar for max mpg, but the best way I found to let my mopar get the best mpg is to let is sit in the f****** weeds when its 4.43 a gallon LOL
 
My 65 will be somewhat MPG oriented when it gets redone. I get 22 MPG with the worn out slant and would like to keep fairly close to that with the 318.

Here's the plan so far:

KB167 pistons @zero deck
302 heads, 1.88/1.60 valves, mild port and polish
Hughes HEH 1523 cam
Headers (Spitfire or similar), 2 1/4" down tubes into a 3" single exhaust.
904 with low gear set
3.23 gears

Sounds pretty mild right? I want a responsive efficient little V8, with a similar power curve to the old HP 273. I want an engine that will not hurt itself and that is capable of going 100,000 miles between major maintenance.

Sure I could go faster, but I drive this car to work on the freeway daily. And I have 2 teenagers that will be driving the car as well. I'll go looking for something else for a pure bracket basher.
 
I'm building my 318 Duster for good mileage and power. MSD-type CD ignition helps a lot (especially for old low-comp open-chamber engines). I'm also going to 800 cfm ThermoQuad on factory iron 360 manifold, 2.5" dual exhaust with X-pipe off stock manifolds, and Crane H-260 cam. Car has 2.76's stock, so those will help with mileage.
 
i had a 87 dakota 3.9 v6 carburated engine stick shift,, ran great,,no clus on mileage,,,too long ago
 
I did one back in the late 70s....
a 74 swinger, 318-2BBL, no AC, manual steering, power disc brakes, 2.76 rear axle, in stock form. Only car I ever ordered from the factory. I added 340 exhaust manifolds and dual exhausts, a lighter advance spring in the distributor, and got 23 mpg hiway. Later on, moving to Idaho, the BBD did not like winter time starting, so I put on a Holley 2BBL and intake from a Ramcharger 360, rejetting the carb down 2 sizes, and it started and ran much better, but MPG went down to 22mpg hiway.
Currently, I am building an 80 Lebaron coupe (the short wheelbase M body coupes were only made in 80-81) with 318, magnum heads, factory cam, 1.6 ratio rockers, low gear set 999 tranny, 2.45 suregrip rear axle, MP ignition, and will likely stay with a single exhaust, but it will be quite a bit larger than stock. I am hoping to make 92-93 magnum exhaust manifolds fit, along with a dakota Y pipe, which is part of the reason why the power steering had to go, along with the column shift linkage, all that stuff is in the way of the better exhaust manifolds. I have replaced the power steering with a manual box, will keep the AC. Will be running 225/60/16 tires on alloy rims (from a Ford Explorer sport trac, 4.5" backspacing on sport trac wheels). Not sure which carb I will use yet, probably a TQ. I may add aluminum bumpers from either a fairmont or a camaro, they supposedly are a good fit on late M body cars. I am aiming for 24-25 mpg.
From my experience over the years, I can tell you that the most effective option for good gas mileage is a light foot....
 
68 Sedan said:
The last Dak I owned was an 93. It was a V6 xcab long bed SLT and @ 161000 miles still got 21.1 on the highway
Click to expand...
Aerodynamics is the problem with the dakota. It has none....
I bet the 3.9L would do well in an A body coupe, especially with an OD tranny and 3.2 axle, or a later model low gear set 904 tranny and 2.4 or 2.7 axle.
 
If you want max MPG try to find a Feather Duster or Dart Lite. They were rated at something like 34MPG back in the early 70's.
 
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