MPG for 318's, 383's, & 440's

[THE COLONEL]

Ok.  Last year was going to be the year I was gong to change the engine in The Colonel, to a 450hp, 440.  After my guy and I discussed money, it was too fine of a line if something else had to be done that we came upon.  So...this year, I have saved more money, and it should be getting done this year.  But with gas prices, I'm not sure I want the 450hp 440.  I have been thinking about getting my 318 rebuilt.  When I bought the car off of Oldyeller ( a member here a few years ago ) I was told it was the original engine, and I have looked and can't find the VIN anywhere on it......that's another story.  So with all that said, what kind of milage do you get with your engines.  Is it that big a difference between a 318, 383 & 440 if your not racing it?  With my kids in the car ( most of the time with me ) I will not be racing it, and just use it to cruise.

If ya'll can post your HP, engine size, and milage you get that would be great.  Thanks for the help.  Hopefully this thread will make my decision on what I will do.

[G-man]

Im interested in knowing myself.

If this helps...

512ci (440) stroker. 525 Horsepower, 572 ft/lbs of torque, 850cfm HP Holley Vacuum Secondary carburettor, street dominator single plane intake manifold... closed chamber heads, Tested on the road for MPG... 16-MPG Cruising (stomped on few times -  could probbably push 17-18mpg driven like a grandma). From 2200rpm it already started breaking traction up through to 6000rpm. Very good power down low and pretty efficient for such a powerfull/big engine. Ofcourse... gear ratio and gears help this.

Dunno how good that info will be to you, but, that tells me a well tuned/built 440 will be good enough on economy and still have power to have fun in the back street if u wish. If u dont ever care to have fun with it (on an odd occasion)... 25+MPG out of a well built 318ci.

[Todd Wilson]

My 69 318 car was getting 20-23mpg and after Chryco got done with it it made 26 mpg on the trip home. 230000+ mile motor. I ran along side a 383 car the whole way and it was in the 19-20 range.


Todd

[Rolling_Thunder]

my old 318 2bbl for a 19mpg average...   thats with my foot into it quite a bit.

[Ghoste]

If you primarily just use the car to cruise around with your kids what did you want a fire breather for in the first place.  I think you should rebuild the 318 and continue having fun with the car.

[bull]

A lot depends on the rear end ratio. My '70 Charger with a 383 got great mileage on the freeway because it had really tall gears. On one 323-mile trip I got a little more than 22 mpg at an average of 71.7 mph for 4 1/2 hrs.

[Bluestar]

I remember being amazed at the mileage my 68 383 got, but also amazed that I could actually see the gas gauge needle move when I was on the throttle.  But normal driving, I'd day I was getting 18-20 on a 383 Magnum.

[THE COLONEL]

my old 318 2bbl for a 19mpg average...   thats with my foot into it quite a bit.

That is about where I am right now.

keep the info coming!

[1BAD68]

my 318 4bbl was getting around 22 mpg, after stroking it to 390 cu. it gets about 17 mpg
-automatic, 3:55's-

[CB]

with my old 69-383 I had around 11-13 mpg. Old engine, no highway & heavy foot 

I really hope with the new 69 and rebuild 383 to get around the same but going faster
CB

[IowaCharger69]

my 69 383 2bbl one legger with granny gears got around 20 on long trips. In town however I have no idea.

[Ghoste]

Keeping in mind that it's all relative to the total package too.  I don't know the mileage in my car exactly but I do know for sure that after going from 3:23's to 4:10's with a slightly taller tire, my 383 got about the same mileage.  Not the same obviously, but moving the engine into a more comfortable powerband seemed like it made more effiecient use of the fuel.

[evil1]

This is a very interesting subject , but with out knowing autos from sticks and then gear ratios . It would be hard to compair the MPG between the engines ,when the rest of the drivetrain can make a big difference in MPG as well.

[JimShine]

Driving enviroment makes a difference too. If you are talking city driving, rarely going above 40 MPH and lots of stop and go, the low rear end gear ratio is not best for fuel economy as you need to push the engine harder to take off. However the low ratio is most efficient for highway driving.

We battled this with Transcon Medivac. A high gear ratio rear was bought, but we opted not to use it because it is a long distance driving vehicle. With the help of the Gear Vendors unit, you can cruise at 85 MPH and barely hit 2000 RPM's. It helps keep the gas use to a somewhat reasonable level. The big engine compensates for takeoffs, but it guzzles the gas when you do.

[Mike DC]

       

I've always been impressed with the 383 motors in terms of efficiency.  The mileage isn't great, but it's more than the 383's hp/torque would suggest that you'd get from it. 

The 360 motors are strong runners but they're real gas-guzzlers for the displacement size.


The carb can make a big difference.  850-cfm carbs will make anything guzzle some gas, and even the midrange throttle-response is better with a smaller carb.  Vacuum secondaries are better than mechanical secondaries for mileage. 


--------------------------------------------


Overdrives are great, but watch the rear axle gear even with one.  A Gear Vendors unit is only like a 22% reduction in RPMs.  It doesn't do much good to gain 22% in the tranny, and then turn around and swap a 4.56 into the diff to "take advantage of it." 

A typical modern sports car will keep the axle gear in the very low 3's, and that's even WITH  a lockup torque converter and a 0.60-something overdrive ratio.  (They also tend to have 3.0-3.5 reduction in the first gear ratio, something that a torqueflite isn't even close to.  A T-flite's first gear is a 2.45, which is so high that it's actually sometimes closer to a modern 5-speed stick tranny's 2nd gear ratio.)



I haven't run it myself, but on paper I really like the GM 4L60E tranny swap that Keisler is pushing.  That gives a lockup torque converter and something like a 0.65 ratio in the overdrive gear.  The first gear is in the 3's too.  So the whole thing's gear spread is pretty much the best of all worlds. 

It's a lot of money though.  I think a good bit more than a GVOD. 

[Doc]

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