Fuel economy question...

[Triplegreen500]

My driveway is at 1601' elevation, and "town" is in the valley (200' or so), so I'm up and down hills a lot.

 

[WileE]

OK... real world experience, from during the "gas crisis" of the 70's : my stock 318 Charger got about 13mpg... stock 318 Sport Satellite about 15 mpg, until I modified it, then it got almost 15 mpg but hauled ***... ( I didn't drive "gently" ) we did a lot of " tweaking" and tuning back then to boost customers MPG, best results were up to 18 driving softly as I recall

 

[Slap Stick]

Okay....back in the 70s both the 72 and 73 Chargers with 2.76 gears would reliably get 20mpg. So did my 383/4 Sport Fury with 3.23 and dual point while running the air.
And, believe it or not a friend's 70 440 Charger with RV cam and 4.10s would get 20 at 55 mph. Took a bunch of tuning to get those cars to do that.
Gas was mo better back then.
I would expect them to drop 2mpg today. Corn doesnt make good go juice.

 

[turbine68rt]

My driveway is at 1601' elevation, and "town" is in the valley (200' or so), so I'm up and down hills a lot.

Not exactly the best terrain for economy.

 

[33 IMP]

My driveway is at 1601' elevation, and "town" is in the valley (200' or so), so I'm up and down hills a lot.

See, there's your problem, too much uphill driving! You should always try to go downhill only!

 

[Jeff Peterson]

I know it's not apples to apples, but I have a really nice '84 W150 w/ a 318, it had a 2 barrel and ran so nice and smooth you would of swore it had efi.
Anyway, I put eddy 4bbl intake and 600 Holley on it, just so it had "some more suds" and fuel mileage actually increased.

 

[Kern Dog]

@tripplegreen500

My 73 satellite 61,000 mile 318 with 2.73 8.25 gets real world average 14.5 MPG.

Almost bone stock 2 barrel with a partial open element air cleaner, timing at book spec 0 degrees, and dual 2" exhaust.

My car is a stripper so likely weighs less than yours (3700# without me, but with a spare, jack and speaker box in the trunk).

I say you are in the ballpark

Reminder......There were NO 2.73 ratio Mopar axles. The 8 1/4" had a 2.71 though. The 8 3/4" axle had a 2.76.

 

[66Satellite47]

I know it's not apples to apples, but I have a really nice '84 W150 w/ a 318, it had a 2 barrel and ran so nice and smooth you would of swore it had efi.
Anyway, I put eddy 4bbl intake and 600 Holley on it, just so it had "some more suds" and fuel mileage actually increased.
View attachment 1129894

When I swapped out the 318 2bbl in the van for a 360 with LD4B & Carter 650, Comp260HE & cheap headers, picked 3 MPG average & 5MPG towing the 5500# race car & trailer. And the 360 could go up hills with no trouble.

 

[440 4 speed]

When I swapped out the 318 2bbl in the van for a 360 with LD4B & Carter 650, Comp260HE & cheap headers, picked 3 MPG average & 5MPG towing the 5500# race car & trailer. And the 360 could go up hills with no trouble.

We have a 1986 360 camper van Dodge 350 series. Bought it in 2009, 59000 Kilometers. Had a Rochester quadra jet. Took it on a cruise to Texas and other points. It was a DOG no performance 8-9 miles per gallon Canadian. Had the carb rebuilt, still not good. Put a 4640 Carter on things improved. Then my friend did a little work on a Thremoquad I had. Now I have gotten as much as 17.5 mpg Canadian. Also don’t have to put it into 2nd going up a certain hill.

 

[Don Frelier]

My 84 gran fury 318 la got 24 mpg when it had around 50k on it and that was driving around 70 mph. Just a lock up torque converter no overdrive.

 

[Tman100]

I have a 66 polara. 318 has a mopar performance purple cam (basically a 340 cam) heads are stock with port work and a 360 4bbl intake port matched. With the car having 2.94 gears I consistently get 18-20mpg if I drive it nicely. Has a 1406 edlebrock carb (600cfm). Timing is 12 idle 35 mechanical and 52 all in. The jetting of your the carb and timing made all the difference in mileage and power. The big 4200lb c-body moves quite well. I’d say with some tuning you should be able to get a few more MPG out of it. My 318 is also a 1978 duster motor.

 

[Triplegreen500]

Well I was doing some other electrical stuff on the car yesterday (3.5h to get the horn sorted out and working), so I checked timing while it was still warm. Unhooked the vacuum advance and corked it, 10*BTDC at idle. The book says TDC +/-2, and it runs well, so I'm just going to leave it there. I certainly don't want to retard it, but I'm hesitant to advance it much further. Thoughts? Advance till it pings, then back it off? Or leave well enough alone?

 

[toolmanmike]

Well I was doing some other electrical stuff on the car yesterday (3.5h to get the horn sorted out and working), so I checked timing while it was still warm. Unhooked the vacuum advance and corked it, 10*BTDC at idle. The book says TDC +/-2, and it runs well, so I'm just going to leave it there. I certainly don't want to retard it, but I'm hesitant to advance it much further. Thoughts? Advance till it pings, then back it off? Or leave well enough alone?

10° before is my baseline. You can advance it a degree or two at a time and test. Listen closely for detonation though. It might run better close to 15 but there are some factors to make it so.

 

[Triplegreen500]

10° before is my baseline. You can advance it a degree or two at a time and test. Listen closely for detonation though. It might run better close to 15 but there are some factors to make it so.

Good to know, thanks. Looking at the book, I was already 10* advanced so I didn't want to push it. But I also figure now's as good a time as any to advance a little, with it being 95 degrees outside...if it's gonna ping, it'll be when it's hot!

 

[YY1]

advance until ping under load, then back off until no ping

 

[Triplegreen500]

advance until ping under load, then back off until no ping

Yes, that much had latched itself onto a brain cell I didn't drown back in the day

 

[Armycopter]

383 magnum 4 barrel and I get about 11MPG. I use 93 octane fuel.

 

[Kern Dog]

My 84 gran fury 318 la got 24 mpg when it had around 50k on it and that was driving around 70 mph. Just a lock up torque converter no overdrive.

Those had the A 999 transmissions. 2.75 first gear instead of the 2.45 that the older 904s had. 2.2 axle gears though!

 

[Kern Dog]

advance until ping under load, then back off until no ping

In some cases, it can be hard to get a stock 318 to detonate. They claimed a 8.2 compression ratio but that is BS...

 

[YY1]

You'd be surprised how many people don't get the under load part.

My 73 wants the book spec 0*. Any more and it pings.
I wish I could run more.

...and that '84 engine could have been a 9.2:1 roller, and could have had 2.45 gears.

The best MPG 318 I ever had was a 67 (again, a 9.2:1 engine) in a stripper white hat special Coronet 440 with 2.76 7 1/4 axle. IIRC the only option was automatic trans.

That engine burned so clean, clear water dripped steady from the tail pipe, and so smooth, you could balance a bic lighter on end on top of the air cleaner. 100% bone stock, but kept in tune religiously. It averaged 18 and got 22.5 on my highway trip from OH to FL (slam fully loaded, and pulling a small u-haul trailer).

I didn't have a timing light back then (and only recently got one) so I always used that "advance under load until ping" (and still do) method. I actually used to nose up to a telephone pole and push against it, so I didn't have to keep getting in and out and travelling up and down the road. That method also helps hone in on a specific RPM that might ping more, since you can hold it where you want it with the same load, for as long as you want.