SLANT 6 a GAS GUZZLER?

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brandon2701

brandon2701
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Howsit you guys my name is Brandon and I live in hawaii and recently bought a 73 dart swinger :D
a very fun ride, though i am new to the engine, because my father has a 70' cuda therefore i've been around more big blocks than small blocks.
How efficient is the slant 6 on gas and is there anyway to increase that efficiency?
 
pretty efficient on gas, maybe 22-24 mpg?

best gas efficiency and life can be reached on it with a 2bbl and an open exhaust system to quote what Bruce taught me
 
DarTT said:
pretty efficient on gas, maybe 22-24 mpg?

best gas efficiency and life can be reached on it with a 2bbl and an open exhaust system to quote what Bruce taught me
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WOW.....im pretty sure my gas gauge is broken then kuz she's getting empty pretty quickly...atleast thats what it is telling me, thanks man.
 
I think a more typical mileage figure (on a well-worn, non-rebuilt, at best averagely maintained slant6- in other words, almost all of them) would be in the high teens.. say 17 mpg.
 
brandon2701 said:
Howsit you guys my name is Brandon and I live in hawaii and recently bought a 73 dart swinger :D
a very fun ride, though i am new to the engine, because my father has a 70' cuda therefore i've been around more big blocks than small blocks.
How efficient is the slant 6 on gas and is there anyway to increase that efficiency?
Click to expand...

Hey Brandon,

Our 1969 Dart Slant 6 225 Auto, just went to Smokies from around Cincinnati Area (310 miles 1 way) and had an average milage of around 22mpg with a single barrel carb, new air and fuel filters and an oil change. No other tune up parts were used before the trip and the last complete tune up was over 2 years ago!!
This car is single exhaust with a turbo flow muffler.
Our fuel tank sending unit had been replaced earlier and STILL will stay on full for a while then drop all of a sudden to 1/4 tank then will run forever on 1/8 tank mark, but when it hits empty on guage you better pull into a station becuse it's REALLY empty! LOL!! It's tho only one of our Darts that does this!
Increasing efficiency? New Parts installed as follows:

spark plugs
air filter
fuel filter
sending unit in tank
points
condensor
rotor
cap
wires
rebuild carb
replace vac lines
check for vac leaks
set timing

I think the 22mpg average I had on the trip were mostly highway miles (60-80mph) in mountains, and that 22 average would be about as good as could be expected! Was hoping for 27mpg but at least wanted more than 17mph!
22mpg average? I'm good with that!!!:cheers:

Made me chuckle this morning remembered something from Sat. Had a guy look at BOF our 67 318 Dart with 4 bbl edlebrock 600cfm, dual exhaust. Him and his wife were driving one of the cars the gerbals on the commercial are driving, don't know model. small and square shaped. Anyway before I lit out with the hubby on test drive, the wife asked, "What kind of gas milage does it get?"
I said, "Who Cares!, That's not a main concern with a car like this. If you have to ask a question like that you have no business with a car like this, just go get another of what you're already driving"!!!

Strange looks from the wife then. I said,"If ya keep you're foot out of it and don't drive like Indy 500 you should be ok with the vacume secondary on the carb, but as soon as you burry your foot in it, you'll be dumping the gas!!!

Good Luck!8)
 
The 73 will already have electronic ignition. Not much you can do there other than screw around with timing and advance curve. Carb, exhaust, and gear ratio are all thats left to alter. Good luck with it.
 
brandon2701 said:
Howsit you guys my name is Brandon and I live in hawaii and recently bought a 73 dart swinger :D
a very fun ride, though i am new to the engine, because my father has a 70' cuda therefore i've been around more big blocks than small blocks.
How efficient is the slant 6 on gas and is there anyway to increase that efficiency?
Click to expand...

My 73 Custom has a 1 bbl, 2.76:1 gears & auto. It is closing in on 300K miles using about 1 quart of oil per 800 miles. (It was worse, but the loss was from a leaky oil pan gasket and front main seal.) On the road I get 23-25 depending on speed and A/C use. Around town, I get 15-16. The only significant modifications are 15" wheels, oversize exhaust manifold, no carb heat, and a 2¼" exhaust system with a "Turbo" muffler.

Like any other engine it responds to good tune, free flowing exhaust, good fluids, and good driving techniques. In terms of improving efficiency, a lot is going to depend on how the car is used. Some of the things that will make a car miserly on a 500 mile jaunt down the interstate in Nebraska won't work too well on a small, crowded island.
 
My slant in a high state of tune on the highway would get about 22 and around town it would drop to 16 or so.
 
My mpg increased after doing the electric radiator fan conversion.
It also reduced the engine noise. Now I can hear the exhaust and air going into the carb better.:-D
 
Where'd you get the electric fan? Mine is getting 18mpg at best after a massive tuneup in my '72 scamp. Timing still needs to be adjusted though. I was done to about 14-15mpg before I got rid of my dying distributor and switched to electronic ignition.
 
scamperly said:
Where'd you get the electric fan?
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A local junkyard. It's off a mid-90s Toyota Corolla and uses a Hayden adjustable controller from O'Reilly Auto Parts.

I mounted it on the front of the radiator just because it was easier that way. Been working fine so far.
 
No matter what I did to any of the 3 slant 6 engines I had, they all guzzled gas like it was a whine-O outta jail from an over the weekend stay let loose into a Octoberfest free beer give away with given a notification that tomorrow thw world will end, so drink up before noon tomorrow!

They all suck and have never personaly met anyone with one worth it's weight in dog crap.

Best I ever have gotten is 16 on the Hwy.

No before anybody starts bashing me and telling me I don't know what I'm doing, I've been at this game 20+ years so you all can sit on a hot outta the fire poker before I beileve a one of you.

No way no how are these dino aged engines getting great mileage unless there in a time capsule fresh.

I'll get 22 MPG's outta my 318 and have nailed 20 mpg's from my 4bbl 360 in a 3660 lbs Dodge Magnum.
 
rumblefish360 said:
They all suck and have never personaly met anyone with one worth it's weight in dog crap. [snip]...I've been at this game 20+ years so you all can sit on a hot outta the fire poker before I beileve a one of you.
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Sounds like you might be having a bad day. Hope things get better for you, cause you're a good dude.
 
any car should be able to get decent mileage in relation to its weight if you drive it normally (this is why I like the laws of physics, they cant be broken!) bad gas mileage is usually due to any of the following
1: in need of a tune up, plugs, wires, filters, etc.
2: low air pressure in tires, over size tires creating excessive rolling resistance or rubbing
3: brakes dragging or bad wheel bearing
4: carburetor dirty or adjusted to rich
5: transmission or clutch problems, slipping or dragging
and as always the biggest difference is the driver
 
Anyone here ever fuel injected a slant six? I bet that would help mileage. I also heard you can use the fuel injection from a buick V6.
 
rumblefish360 said:
No matter what I did to any of the 3 slant 6 engines I had, they all guzzled gas like it was a whine-O outta jail from an over the weekend stay let loose into a Octoberfest free beer give away with given a notification that tomorrow thw world will end, so drink up before noon tomorrow!

They all suck and have never personaly met anyone with one worth it's weight in dog crap.

Best I ever have gotten is 16 on the Hwy.

No before anybody starts bashing me and telling me I don't know what I'm doing, I've been at this game 20+ years so you all can sit on a hot outta the fire poker before I beileve a one of you.

No way no how are these dino aged engines getting great mileage unless there in a time capsule fresh.

I'll get 22 MPG's outta my 318 and have nailed 20 mpg's from my 4bbl 360 in a 3660 lbs Dodge Magnum.
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V-8 guys can NEVER seem to get decent performance or mileage out of slants. Dedicated slanters get 20+mpg out of their engines all the time. I don't know what I'm doing, and even I can get 20 hwy out of my warmed up slant. Funny how that works...
 
vynn3 said:
V-8 guys can NEVER seem to get decent performance or mileage out of slants. Dedicated slanters get 20+mpg out of their engines all the time. I don't know what I'm doing, and even I can get 20 hwy out of my warmed up slant. Funny how that works...
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Exactly. After a couple years of reading the slantsix.org board and listening to SlantSixDan's advice, I have upped my mileage from 10 to 23mpg. Not only that but my slant has more power as well.

If he wants to be stubborn then let him be stubborn because everyone and their mother knows getting over 16mpg highway with a sl6 is easy unless you're in a big truck or van.
 
ESP47 said:
Exactly. After a couple years of reading the slantsix.org board and listening to SlantSixDan's advice, I have upped my mileage from 10 to 23mpg. Not only that but my slant has more power as well.

If he wants to be stubborn then let him be stubborn because everyone and their mother knows getting over 16mpg highway with a sl6 is easy unless you're in a big truck or van.
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What sort of stuff have you done to yours? I'm very interested to hear, as I'll probably end up doing it too.
 
Super Six setup
2 1/4" exhaust
HEI electronic ignition
10* BTDC initial timing
7 1/4" 2.76 rear gear
904 stock tranny
NGK plugs
Close to stock 195/70/14 tires
And basically just removed all the useless weight from the car

I could still recurve the distributor to get a little better mileage and then put in a 4 speed OD to put it over the top. After that the other mileage upgrades seem like theory at best.
 
Well I did the electronic ignition already, waiting to get headers so I can do the exhaust and put on a 390CFM 4bbl holley (with offy intake). Looking at doing an electric fan conversion too. Anyone else have ideas on how else to improve performance and mileage?
 
RonnyB said:
Sounds like you might be having a bad day. Hope things get better for you, cause you're a good dude.
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Thphhhh, my day is great, thanks.

vynn3 said:
V-8 guys can NEVER seem to get decent performance or mileage out of slants. Dedicated slanters get 20+mpg out of their engines all the time. I don't know what I'm doing, and even I can get 20 hwy out of my warmed up slant. Funny how that works...
Click to expand...

You assume to much. You know whaty happens when you disassemble the work assume right.
 
ESP47 said:
Exactly. After a couple years of reading the slantsix.org board and listening to SlantSixDan's advice, I have upped my mileage from 10 to 23mpg. Not only that but my slant has more power as well.

If he wants to be stubborn then let him be stubborn because everyone and their mother knows getting over 16mpg highway with a sl6 is easy unless you're in a big truck or van.
Click to expand...

It took you years to figure out what makes'em tick for better mileage? When I read on, below, I can not for the life of me believe what I read.

ESP47 said:
Super Six setup
2 1/4" exhaust
HEI electronic ignition
10* BTDC initial timing
7 1/4" 2.76 rear gear
904 stock tranny
NGK plugs
Close to stock 195/70/14 tires
And basically just removed all the useless weight from the car

I could still recurve the distributor to get a little better mileage and then put in a 4 speed OD to put it over the top. After that the other mileage upgrades seem like theory at best.
Click to expand...
The difference in adhusting my 360 in a 4000lbs car was less.
OE parts were reused. twin cats on a new exhaust that followed the pattern of the OE dual exhaust and I added weight to the car with more sound deadener, 2 amps and a sub woffer. OH, a real spare tire over the colapsed donut.

I'm sorry fellas, I think that the constant 19 - 20 mpg's out of a V8 with twice the power and torque is well worth the dumping of the slant 6 hands down. Adding the MSD was also a mileage getter with an extra 2 mpg's on a solid every time any time bassis.

This car also started off as a 10 mpg Hwy. car that did still sport that catastrphy of an ignition, the "Lean Burn" which was tossed in favor of the old Orange box set up that the dealers used to carry in stock because the lean burns were so bad. This ignition swap was standard pratice. So don't bother running some crazy crap up the tree on me for the swap.
 
I've never gotten better than 20 with a slant on the highway. And that was being very careful with it. Hell I get 19.4 with my 7800 pound Cummins 4WD 2500 on the highway. Where the hell is the sense in that?
 
I have a 73 scamp with a slant six and a three speed manual on the floor. DO you think i'll get better or worse mileage with the manual?
 
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