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Slant Six mpg's?
- Thread starter vintagetin
- Start date
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ESP47
Well-Known Member
For a guy who hates slant sixes, you sure do post in the slant six forum often. Do you have some kind of secret slant six fetish you need to talk about? You can't stay in the closet forever. :toothy10:
The slant 6 "gang" doesn't claim that they get 30+ like crazy. In fact I'm going to call BS on anyone that claims to get 30mpg with a slant unless it's a finely tuned stock Feather Duster or Dart Lite.
18-19 around town and 22-23 on the highway are about as good as you can get with a 904 tranny and a 7 1/4" rear w/ 2.76 gears. You can slightly up that with an OD transmission and/or a slant specifically built for economy.
Guys that are claiming to get much more than that are either exaggerating, aren't calculating and testing their mileage correctly...or they're just really lucky and have an engine, carb and car that just work perfectly together.
TurdFerguson
Banned
TurdFerguson
Banned
According to some of them /'rs....
they can everything you can do, better
they can do anything better than you....LOL
That's the 2nd time you've mentioned that.
Engine Weights:
Slant Six 475 lbs.
273-340 "A" V8 525 lbs.
360 "A" 550 lbs.
361-383-400 V8 620 lbs.
413-426W-440 V8 670 lbs.
Street Hemi 765 lbs.
Slants are a lot lighter than I'd expect for an overbuilt engine designed in 1959, and just like V-8's, can be lightened with aluminum parts. Why do you keep mentioning how heavy it is?
grimreaper
Cross Member
My 225 in a 64 Valiant has averaged 16.7 since I got it. I keep track of all of the gallons that go into the tank and divide the miles on the odometer by the total gallons so for four years of only summer cruising it has done 16.7 MPG.
Something else to keep in mind is inaccuracy with the speedometer/odometer. Even if the right gear is in the transmission, if the wheel size or tire size is off from EXACTLY what that gear was made for, they will both read incorrectly. I'm averaging 8/12 (city/highway) in my Dart though it is a 318, but at 55 mpg, my speedometer reads 50.
I here you :happy10: I thought I was getting 27 to 29 MPG till I figure the wrong wheel and tire size I am running :-D
It's hard to say unless you have a friend with the correct mph odometer to follow and get a reading at lets say 60 mph . then take a HWY trip for 100 mile then refill the tank and do it again on the way back :happy10:
I am getting 24 on the HWY in my 66 170/ offy 4 bl 390 Holley and split manifolds and I am replacing axle bearing and seals, This might give me an extra mile or two :happy10:
Very good point Sinister 8)
And it's not something I realized until last summer either. I was following my dad out to get some BBQ. When we got there I asked him why he was going so slow and he said he somehow managed to set cruise at EXACTLY 55, and left it there. I was on his a$$ the whole time because I thought he was going 50!
There are a definitely a TON of little variables (like altitude, temp, driving habits) that can have a huge effect on gas mileage.
trapster
Well-Known Member
Every time I take out my car the carb is dry. So I think the gas is evaporating faster than I am using it. 
I am guessing I am getting around 14 or 15 mpg filling up every other month or so.
I am guessing I am getting around 14 or 15 mpg filling up every other month or so.
bruceo2011
Still waiting for Y2K
My '76 Dart 225 super six, 904,2.76,215/70/14's averages 18/20. My '65 Valiant 170,904,3.23,185/70/13 does 20+. Picked it up late last summer, so don't have a real good handle on it's MPG. The day I have to worry about gas mileage, I sell the cars and start collecting stamps. AND I love the looks and stories from people who had a slantly in their past.
TurdFerguson
Banned
Because those number are not right........
If you stuck all the regular bolt on's into the picture, the v8 would weigh a lot less.= aluminum intake, headers, water pump[early had iron] and even aluminum head's', but hey....whatever you say.
slants have the aluminum intake, headers....and thats it.
still stuck with that tank of an iron head that weighs 'close' to the block does.
and since when does an iron '3.58' crank add 25lbs over a steel 3.31 crank?? really??
Lets look at that 4 a minute...
HP 10.5 340 pistons from the factory weigh more than a 360 piston by a considerable amount 'in the world of pistons' let alone the bigger bore.
then the windage tray, the diff main bolts.......ah heck it's obvious those number are garbage by the way it say's the 318 weighs the same as a 340........meanwhile the 340 has a way larger bore,pistons,rods,tray,intake, valves,springs......I could go on but my point is made that the info you have listed is incorrect, wether the slant is lighter or not.
I will go the scale and start weighing....
madmax/6
Well-Known Member
I get close to 3 mpg with my race slant.And race gas aint cheap.My stock aluminum block 62 Signet with 2 1bbls gets 20mpg at a steady 70 with 323 gears.Guzzi Mark
When gas was lowered the first time, in the Carter years, I pulled the 273 Commando with 72 340 heads since it had too much compression. I built a 170 /6 with the 4 speed and 2.76 gears. I could get 30 mpg on the highway. It was not stock. Mild Direct Connection cam, milled heads, cc'd chambers, 2 barrel carb and intake.
USAJon
Maryland U.S.A.
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1985 Dodge Ram 100 short bed stock slant six 4 speed overdrive 24 MPG empty in overdrive on FLAT hwy. driving in Delaware. here it is with a little over 1 ton o'sand..MPG unknown short trip say 20 miles..no overdrive used.
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Well, at least your honest in saying it was a 170 and not stock.
I love the 225 guys claims of 30+ in there rides, even more so in there trucks at 70+ mph and carrying 2 toms of heavy stuff on top of it.
Sorry fella's, I don't buy it and never will until you give a ride. And even then, unless I know you and trust you alot, I'll consider your "It's stock as a rock claim" invalid.
Looking foward to the day I'm proved wrong and until then, I just can not beileve a 225 / automatic is gonna get 30+ with a all stock car.
ESP47
Well-Known Member
If you want accurate mpg readings, go over to the .org site and see what those guys have to say. You wont find many claiming anything over about 24mpg. You might have guys saying "I had my best run of __mpg doing 55 across the plains", but no one claiming to get 30 with a non Feather Duster...and especially not a truck.
Speaking of trucks, I just bought a 78 D100 with a super sixed 225 and 3 on the tree. Got 15mpg on the way home from where I bought it about 3 hours away. Looked under the hood a bit closer when I got home and noticed a ton of things not connected correctly. Going to be dropping in a 4 speed OD here when it gets warmer and also going to lower it a little bit so it doesn't sit like a turnip truck. We'll see what I can get. I'm hoping for 21mpg or so, which would be great for a truck. I'll have to post my results here after I finish the project.
A 4spd. OD? Go for it bro! Go for it!
Ha, Ha! I have'nt had anything that was "stock" since I was 17 and that was a long time ago. It was in a 64 Barracuda, which is pretty slick aerodynamically. It had a vacuum gage which helps also.
vintagetin
Active Member
I calculated my fuel mileage farely accurately. I got up on the interstate to see if my odometer followed the mile markers. It was consistant the whole 20 miles I was on the interestate...so it must be pretty close. I built a seperate tank with a clear level on the side and measure the amount of fuel that was in it. I drove 20 miles and could clearly see how much fuel I burned. My '66 Charger with the '76 360 (rebuilt, nice and fresh), grounded head (resurfaced to add a little bit of compression) 2.73 rear gear (I believe..haven't checked) at 55-60 mph, and coasting down the hills I got 22.5 mpgs! I bet, a fresh slant 6, 170, or 225 could manage ALMOST 30 with an OD transmission, and skinny tires. Weight does not matter on the highway so much. Think about it..down the hills...weight would help when coasting. It would only really hurt you in the city having to get up to speed all the time.
73_Dart
Well-Known Member
I would gladly take some of your guys mileage.
Im only getting 7 mpg in town. Thats without idleing any. Easy on pedal to. Just replaced distributor cap and plugs. New air filter and fuel filter. I dont know whats wrong with it.
its a 73 swinger with 225 slant 6 automatic. All stock.
Im only getting 7 mpg in town. Thats without idleing any. Easy on pedal to. Just replaced distributor cap and plugs. New air filter and fuel filter. I dont know whats wrong with it.
its a 73 swinger with 225 slant 6 automatic. All stock.
Well, rest assured that there's definitely something VERY wrong. Time to learn how to do some basic diagnostics (compression test, check timing and vacuum and read the plugs, for example), or take it to a mechanic to do it for you. My mildly hopped-up slant that runs rich STILL gets double your mileage in city driving. And I DON'T drive like grandma...
73_Dart
Well-Known Member
I wondering if there is a vacuum leak. my hoses are old and cracked. They need replaced. but I cant find the exact hoses for my car, because the one end has a fitting type thing on it. Cant get same part as on it.
ESP47
Well-Known Member
73 Dart, if you don't have the tools you'll need a vacuum gauge and an engine analyzer kit that comes with compression tester and timing light. All together it should run you about $75. There are old Craftsman engine analyzer kits on ebay for cheap. After that we can direct you on how to go about tuning your car. The tools will pay for themselves in a month on the gas you'll save.
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