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What can you reasonably expect for fuel economy?

383 9.8 to one compression. 650 Holley carb. 3:55 gears. Manual four speed A 833. 15-inch tires 28-inch height. Have not checked the milage for a while after motor is getting broke in pushing 4, thou. mile on it. Last check on milage was around 9.8 miles per gallon with not putting my foot through the floorboard. Running 93 with 10 percent ethanol. Have not checked it while running the A/C.
 
Cranky said:
Lots of cars of the 50's had OD's in them. Thought that was a bit odd with the way gas prices were back then but on the other hand, it saves on wear and tear. Both of my 1st gen Dakota pickups are V6's and with 235/75-15's, if you're not doing 80 when hitting a bridge, the will shift out of OD. Both trucks have 3.55's and just don't have the nuts to pull taller tires but they do with a tire that's close to factory tire size of 205/75's and get better mpg but if you go even smaller (I've done that too), the mph and the pep gets better. Imo, the V6 should have come with 3.90 gears at least and would be even better with say 4.30's! Had a 92 Dak with the 5.2 and 3.90 gears that pulled down better numbers when driven brisk with 12mpg being the worse in town when being meaner than hell on it but the V6's will get just as bad or worse when being mean to them.....ask me which one was more fun!!
Click to expand...
Ain't nothing wrong with those old "Magnum" V-6's (V-8s with two cylinders lopped off, but sharing a lot of internals).
Yeah with modern OD's - the '04 Ram 5.7 of mine (bought new back when) came with 20's on it (ugh) that Dodge was
actually selling with 3.55's at first.
They eventually came to their senses and made it a mandatory option to get 3.91's when those 20's were selected....
which mine has, but to be honest, with two OD gears in the 545RFE, a higher numeric ratio still would probably have
been better.
The OD is so severe in that transmission (plus lockup convertor, of course) that I'm thinking at least 4.10's or even more
would be better.
As it is, around town and up to highway speeds, I just keep it in "tow/haul" mode to keep the convertor unlocked.
 
Cranky said:
Until they get a bit icy in the winter time....
Click to expand...
True dat. Fortunately, we don't get that much 'round he-ah. :)
It is funny when it starts snowing up here on the side of the ridge - but the highway down the valley below,
it's raining.
Elevation difference, you know...
 
moparedtn said:
Ain't nothing wrong with those old "Magnum" V-6's (V-8s with two cylinders lopped off, but sharing a lot of internals).
Yeah with modern OD's - the '04 Ram 5.7 of mine (bought new back when) came with 20's on it (ugh) that Dodge was
actually selling with 3.55's at first.
They eventually came to their senses and made it a mandatory option to get 3.91's when those 20's were selected....
which mine has, but to be honest, with two OD gears in the 545RFE, a higher numeric ratio still would probably have
been better.
The OD is so severe in that transmission (plus lockup convertor, of course) that I'm thinking at least 4.10's or even more
would be better.
As it is, around town and up to highway speeds, I just keep it in "tow/haul" mode to keep the convertor unlocked.
Click to expand...
Yeah, the V6 isn't a bad engine at all and imo, I think it's a good step up over the /6. The V has more pep too and should have with the little bit of extra cubes. Had a 74 D100 with the /6 and no options and it would pull down good mpg IF you had an egg under the loud pedal but the D series trucks were heavier than the Dakota trucks but mpg numbers were pretty much the same as the Dakota when driven the same except that I did squeeze out 20 mph with that old pickup one time and that drive was the most boring tank ever! My /6 67 Dart would pull good mpg numbers with the 3.91 gears in town...I'm talking about 20+ without driving with an egg under the pedal but it sucked gas on the highway. Thing is, it wasn't on the highway much. And of course, we didn't have to contend with the ethanol bs that everyone knows (or should know) that even the 10% crap can reduce mpg by 15%! At least that's what I noticed happening in my stuff when it first started coming out.
 
Although I never did a in depth study of my 71 Challenger 440 6 pack with 4.10 RAR, it seems to get fairly impressive mileage on the highway, somewhere around 14-15 mpg.
That being said I don't care at all for driving it on the highway. With those gears, I don't go much over 60 mph, and seeing how everyone averages 75-85 mph it makes for white knuckle driving putzing along in the right lane while everyone flies by me.
My Challenger convertible 383 4 barrel with 3.23 RAR, my mental calculations put it in the 11-12 mpg range highway.
I haven't had my Magnum 360 4 barrel on enough highway travel yet to have developed a good ballpark estimate of how it does, but suspect its over 15 mpg.
People I've told about the '71 dispute that the mileage can be anywhere near what I feel it gets, but I've also heard a number of other owners of 340 and 440 six pack/six barrel cars claim over the years that their cars do pretty well on highway travel. The theory being the engines are pretty much loafing in that mode, running on the center 2 barrel the high rpm not putting much load on the engine.
Back 40 years ago when the SIAC club for Challengers and cudas was big, there were routinely stories in the newsletter where T/A and AAR owners claimed they were getting high teens on road trips to shows.
What amazes me is how well gas engine engineers have optimized performance, fuel economy and emissions over the last 50 years. My '21 6.4 hemi Ram 2500 crew cab has shown on the dash readout over 21 mpg on highway trips (my feel is that the dash readout is about 5% optimistic). I have got over 11 mpg calculated towing a 24' enclosed trailer with a ~3700 pound car in it, and the trailer isn't even a V nose. But that is a different subject than this thread on vintage Mopars mpg.
 
get behind a semi and ride in the draft............... you will get good mileage........... watch out for flying tire debris and rocks though !
 
I took the Charger out for a small road trip last weekend, about 170 miles. First trip since i put her back together. 508 cuin, 3.23, auto with stock converter, small roller cam. Some, but not much stop and go driving. Probably 40% highway, 40% back roads. 13 mpg.
 
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