What kind of mpg's can you expect from an auto SB A-body? The engine doesn't necessarily have to be built up. But something around stock. Is there any ways of improving it to get around high 20's on highway? Personally I drive about 60 mph on the freeway, but occasionally go 70 on longer trips. Very conservative driver. I know a member here had a 68 Barracuda trying to get 30 mpgs but he sold it for his new business.

wow 30 mpg i want that one ,
best i ever got was 16 witha 360 and 21 with a 6 cyl
so idono good luck

No one has any ideas? What about mid-20's?

It would be a breeze to get 25 hwy and more with a little effort.I chose a clapped out Camry(40mpg) and let the SB A body do what it likes.LOL It still gets upper teens and runs low 11's on motor.

Back in the '70s, I think I could pull 20 in my 318 '69 Dart, 1/2 city & 1/2 hwy, but I was in my mid-20s and I goofed around a lot; I really didn't care much about MPG. It was stock, automatic. Jeez, that was 35 years ago...

I had a 70s 360 in my 67 Barracuda FB with an 833 o/d trans and 3.23s. I was getting 19 mpg mixed driving back and forth to work. I never did take it anywhere very far when I had the o/d, so no real highway numbers. I bet it would have done low 20s pretty easy.
Travis..

Someone here had like 70 Duster with a stroker and a GM overdrive I think. 25 mpg comes to mind.

I'd imagine if you geared it high(imagine an OB with high gears to boot), used a ThermoQuad (I love those carbs) kept your foot out and kept the weight down you'd do pretty good.

What thing could be done to improve mpg's? Things that come to mind would be aluminum heads for less weight, lowering the car a bit to reduce drag, lowering the gear ratio down to 3.23 or lower gears, converting to fuel injection (if the carb isn't properly tuned), possibly getting a larger exhaust system and headers for better air flow, lighter-aftermarket disc brakes (like wilwood), aluminum wheels over steelies/magnums/rallyes, etc.

Do you think with all of these combined a stock/mild 318/340 can hit the mid to high 20's? I think what really kills it with these is the higher compression and 3 speed automatic... I know Keisler has a OD trans but that is pretty expensive unless a 518 is modified to fit in there.

Just thinking...

It really depends on what you want out of it. We used to get 17 out of the 340 convertible (727/3.23 open). For mileage you're going to want to look at overdrive. If I were going to build a small block a-body for mileage I'd look for another 5.2Magnum with an A500 and run 3.23 gears.

I think aerodynamics is where you are gonna find the big numbers. After you get the o/d trans, perfect tune, etc. Also, I think 3.23s and o/d is a great combo.
Travis..

Here's one for ya!
I have a mildly worked stroker 440(496)& use a 4-speed New-Process. Wth 2:75 gears it does low 12's @ 117-118mph 1/4 & gives 17 mpg imperial.
Now,on a 240 mile drive to Christchurch in New Zealand I have always just got into town,& if I didn't gas-up at the first fuel station,I never made another 2-3 miles.
Last yr I stuffed the clutch linings on my Dual-Friction Centre-Force after 3 yrs abuse.
So I put in a 727 auto that I keep on hand,& the following weekend drove the same drive again. Guess what! I got to 40 miles short of Christchurch & run out of fuel.
I did my drags & left for Nelson & roughly the same distance from home I run out again.
Fortunately I carried extra fuel as I new I would be short & was curious by how much. I didn't expect quite that much though.
I always drive in roughly the same manner.
A stock 360 I had in the 80's did 23 mpg imperial with 650 D/P Holley; 1"5/8" Headers; LD4B dual plane Edelbrok intake & a mild cam. I don't recall the specs. It was a Code 2 Alliance.
In my charger it did 135mph in the Car Clubs Flying 1/4 mile.
Mike in New Zealand

https://board.moparts.org/ubbthreads/show...e=0#Post3944014

You can read about my last adventure there. Soon as I get caught up on some bills I will be doing another that will get over 30mpg@70mph

The 1988 Chrysler 5th Ave was rated at 23 mpg highway by the EPA. These had the 318, lock up torque converters, and often had 2.2 or 2.45 axle ratios. The 5th avenue will probably be heavier than most A bodies.

The 5th avenues were NOT noted for performance! The high rear axle ratio was one of the primary reasons for their lackluster performance. An overdrive transmission will allow for the low RPM's needed for highway fuel economy, but the lower rear gears will allow for more acceptable performance.

If a person's primary interest is economy, a 2.76 with an overdrive could potentially yield better mpg's than a 3.23 gear in many situations. The 3.23 would definitely yield better performance and probably wouldn't hurt mileage to much. Of course this will depend on where and how the A-body in question is being driven. For example, in an area with lots of steep hills, a 2.76 gear may not allow an overdrive transmission to shift into overdrive very often. In this situation, a 3.23 with overdrive would obviously yield better mileage, assuming the transmission can shift into overdrive and have the necessary power to pull the hills. (and the 3.23 gear would hold the car back better on down hill grades)

The best MPG I got under normal 70 mph hwy driving conditions was 29 mpg.

All the work I did to it yielded about 5mpg improvement over identicle driving conditions with the original 2bbl 318. It had a lot more power through out the RPM range too. It pretty much needed premium fuel but the cost was out weighed by the improvement, cost per mile was down significantly.