Slant Six mpg's?

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vintagetin

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I was wondering what you daily driver guys get for MPG's out of your slant six a bodies with what setup (transmission, rear end ratio, tires etc). I've currently got a 360 b-body that I'm looking to put an overdrive transmission in and gas $$ is starting to creep again. The ole 360 isn't terrible, it averages 16/22 (around town/highway) with a manual three speed in my '66 Charger. I calculated this buy using a small gas can with a clear meter on the side and driving exactly 40 miles to see how much I burned. So say the sixes are real good on gas, some say, they are about the same. What do you guys get?
 
i have been getting about 18.6, mostly around town. i have a super six with headers, auto trans, 2,76 rear and 195 70 14 tires, in a 4dr valiant.
i am also wondering what others are getting for mileage, i keep thiinking there is a few more mpg's in there. i have tried several things to improve mileage, the super six, cold ram air, HEI, NGK plugs, bigger exhaust. only the plugs showed a noticable improvement (1 mpg).
for mileage in your b body, you might be better off with the 360. i read somewhere that the 360 has the most fuel efficient combustion chambers of all the small blocks. probaly why it lasted longer than the rest
 
Before I pulled the 225 outta like a FOOL I was gettin about 26.
 
I get about 20 average ,,,,/6-904 7.25 w/294 one legger and factory 13 in wheels and tires.The slant is bone stock(for now) Oh its in a 69 Dart 2 door hdtp.
 
I have a 74 scamp as my daily driver (except winter) /6 with OD manual tranny gears unknown (7 1/4) header small 4 barrel carb single exhaust.As I recall factory /6 cars in the mid 70's would get upwards of 30 mpg with smog system.As i never checked the mpg on my Scamp and since it can now breath a lot better I would guess it get's in the 30 + mpg range and is still somewhat fun to drive.My friends made fun of me when I made this car but not now.
 
Allways the case when building an old car....why not the V8? is the normal cat call. They can and do motorvate the car well.

I never gotten better than 18 on the hwy. but those unknown aged/mileaged engines were not part of the plan. My brother claimed mid 20's at best on the Hwy. His old Dart was one hell of a nice clean 1 owner car.
 
Wow, those mpg numbers are far in excess of what I get with my 63 Valiant Signet with /6. It has been averaging about 16-17 mpg. It has been tuned up and this is about 2-3 mpg more than I get with my 81 Imp with 318.
 
I used to get 21-23mph with a 268* cam,ported head,headered, 2 brl holley carb and 3.55 gears in a '71 swinger w/7 1/4 rear
I ran it with 34* full mech advance & about 48* total @ cruise w/vac advance.
 
I would leave your car the way it is. The mileage isn't too bad. It would cost a lot to do the changeover, as well as a lot of work. You can buy a lot of gas for what it would cost you as opposed to leaving it as it is.
My '69 Valiant 4 door with a decent used 225 out of a '75 duster stock everything, 1 bbl, stock 904 auto, 2:76 7 1/4, 195 75 R14 rear tires got about 25 highway @65 mph and about 18 in town.
To compare, my stock '70 Dart 4 door 318, (everything else the same, gear ratio etc.) got 23 highway and about 16 in town.
The 318 car was a lot better to drive overall, especially on hills and passing.
Your choice, but i would rather have the power and 2 less m.p.g.
Just my 2 cents.
Tom.
 
FlatheadGeo said:
Wow, those mpg numbers are far in excess of what I get with my 63 Valiant Signet with /6. It has been averaging about 16-17 mpg. It has been tuned up and this is about 2-3 mpg more than I get with my 81 Imp with 318.
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Maybe look into a valve job but 1st ..an electronic ignition with a dialed spark curve.

And do you have the 170 or 225?
 
I think 18 was about what my buddy was averaging in his '68 Valaint with the 225 in there, 13 inch wheels, ?? rear gears, and the 904 auto, all stock. From what most people have told me, the /sixes are remembered for being some of the most durable long lasting engines ever (even the Chevy guys had to admit!), but not the most fuel effecient sixes.
 
..........My 67 dart gt made 16-17.....hwy........11-12 in town......pretty tired though........my 76 dart sport.....25 hwy...18-19 town.....my 68 dart 270 dont know as i only drove it 24 miles home.....changed to 340, 727 8.75 with 3.23s......kim.........
 
well my v8's both get about 13town and 20hwy . i still woundlt mind getting better gas outta herwhat do u guys do for better gas milaeage.
 
My '72, when it was a DD, I was getting mid to high 20's. 225 904 7 1/4 Gears? 2 barrel everything stock stuff. Motor was completely rebuilt, new carb....trans was also new a few years before motor was rebuilt. I am going to put it into the Duster this summer and start driving it again.

I figure on putting an electric fan on it to free up some wasted energy.
 
On the ones I've owned....20MPG with a '61 Valiant 170 auto.....22MPG with a '66 225 and a 3 speed.....15MPG in the '78 D150 225 2bbl. 4 speed. All the engines were stock originals with freeway gears. You can add a few MPG's for highway only and subtract some for in-town only.
 
currently getting about 15 mpg with 69 Dart 4 door auto with unknown 7 1/4 gears(likely 2:94). Did the HEI mod, but the carb needs a rebuild, and I am putting better wires and NGK plugs in soon, hopefully the tuning will help a bit.
 
powerwagonpaul said:
... i read somewhere that the 360 has the most fuel efficient combustion chambers of all the small blocks....
Click to expand...

Gasp, the chambers were the same across all the open chamber LA heads, and the 360 gets miserable mileage in my opinion. Look at a newer non hemi 360 truck, they are like 8/12 MPG real world numbers. Lots of people say the 360 pulls like a big block, I say it drinks like a big block. But hey, its only gas and im building one even bigger so what can I say? Look at a Feather Duster or Dart Lite and its specs. Now thats an efficient motor. and its still a 225 six. I think a carb rebuild is the first thing to try, not a rebuilt carb, but a carb rebuild..get it? You can do better than a rebuild service 99% of the time as your stock carb has all the correct pieces for that model, and your model specs are in the carb kit documentation..not parts from a cleaned set of parts bins put together to make a complete carb. Get yourself a kit, some Berrymans, a caliper and some carb cleaner in a can and get in there and spruce it up and put it back IN spec. Second best thing to do is to get an electronic distributor, and then basic tune up stuff. If you can do it outside on a bench, better as youll have better light and some ventilation. Both chemicals stink and seem to linger far longer than your job.
 
I hear the 2 reasons the slant 6 went by the way side,emissions and not able to meet government mpg standards.
 
I like it when someone ask me about milage in my slantys compaired to our 318 cars.
I always respond with a big s--t eatin grin saying, "If ya gotta ask, you don't got any business with a Dart! LOL!!!

To me the gas milage is an after thought when you consider the pleasure both versions of the cars bring our family. We only drive Darts. They are very inexpensive (CHEAP) to maintain, and I can repair 99.2% of all repairs at home with cheap parts. Insurance is cheap too!
Another plus is you usually pay cash for them and don't have the car payment and interest either.
In this day and age, you got to pay the piper somewhere and with all the other benifits of Abody daily driver ownership, gas milage just isn't that important to us. But the wife only drives 1 mile 1 way to work, walmart is 3 miles away. The only time milage entered in the conversations was when we took or 69 slanty to gatlinburg TN last summer! Even then the conversation was, "When are we going to need gas again? I need to go to the bathroom!! LMAO!!!:laughing:
Are you SURE that gas guage is right??!!! HAHAHAHA!!!:hello1:
We get about the same milage in both versions except when you put your foot in it! Then the more barrels, the less milage!
 
Darter6 said:
I hear the 2 reasons the slant 6 went by the way side,emissions and not able to meet government mpg standards.
Click to expand...

IDK about that myself. According to the rabid /6 gang that loves to beat me up, they get 30+ like crazy. Where are they now? IDK.
 
Chrysler boasted that a Feather Duster got 35 mpg. It had a manual transmission and various aluminum parts to lighten the car a bit.

Some common ways to increase gas mileage as recommended during the gas shortage 1970s included:
1. Tune-up
2. proper tire inflation (check often)(can also add an extra pound or two of air pressure)
3. proper brake adjustment
4. easy on the starts (use a vacuum gage "mileage minder-green zone" to help with developing a light foot.
5. Time the traffic lights to reduce the need to stop at red lights (most traffic lights are timed to the posted speed limit)
6. Drive at 35 mph or less when possible to eliminate the resistance of air. Above that speed, the air resistance begins to work against the moving car. (I verified this by putting my hand outside the window with the palm up and gradually increased speed. Try it.)
7. Clean up the underside of the car by using front spoilers or air dams. (Modern cars already incorporate this idea in their designs.)
8. Turn off your car if you have to idle for longer than 15 seconds. This includes red lights, drive-thru eateries, and stopping for trains.
9. Don't use a drive-thru. Park the car and go inside.
10. Switch to a synthetic oil.

This is all that I remember from those dark times. I could have bought a 1969 Hemi Coronet Super Bee for $500 but I, along with everybody, thought gas would never get below $1.00/gallon again. We were wrong, it returned to $0.75/gallon!
 
Yes, that is true though it was also under controled driving conditions. The Feather Duster as you mention beat out Ford and Chevy entries in the test.
 
22 in the summer, 24 in the winter (guess it has something to do with air temp???) stock internally, clifford header and intake, electronic ignition. 72 Duster, 904, 7.25 with 2.94:1, 14 inch rally wheels.
 
I have a 1965 AP6 Valiant.It has a 225 slant 6 with a Carter BBD,extractors,HEI,3 on the tree manual transmission and 3.23 diff ratio.
I am getting 28 mpg (US).
 
I got 27mpg in the 67 dart on a road trip once. I never pay much attention since it doesn't get driven much. But I was a little shocked it did that well. It has about .115" shaved off the head, hooker headers, 2-1/2" dual exhaust, 600 holley, lots of timing, 904 and 7-1/4 stock rear. I'm currently converting it to a 833od so that will be cool to see if it improves over the auto.
 
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