Big Block gas mileage?
 

Anyone know what kind of gas mileage a mildly built 440 with a 4 barrel would get? Also interested in knowing the gas mileage on a mildly built 383 4 barrel. I am wanting to put a big block 4 speed set up in my 68 coronet. And I have been looking at some EFI conversion kits for it. I found one from Mass-flo efi that you only have to hook 3 wires up to your existing wiring harness and it tunes itself. This is going to be my daily driver when I get it running and I'm trying to get away with some decent gas mileage. I think running a fuel injection system may really help with that. I was just curious as to what gas mileage a big block gets in general. Also I am asking how good the gas mileage is when a guy can keep his foot out of it try to keep the secondaries from opening up to often. And not roasting tires at every stop sign and traffic light lol. And how much worse is it than a small block?

When my Dad puts his GTS in a car show, under "special features" he writes:


" Gets 2 mpg!"

I get about 5.

Big block and decent gas mileage is an oxymoron.

You are probably looking at single digits. Although, there are overdirve kits out there and plenty of aftermarket trannies that have some decent gearing in the first few gears and still give you a higher ratio come 5th.

Well.... Thats promising lol. If I can't get any better than that I may have to stick with a small block :(
Which I'm really going to hate doing cause I am doing an R/T clone.

If you stick with the small block and want a little more power do a mild stroker build.:) I have done some EFI work in the past one kit is EZ-EFI kind of the same thing easy install self tuning(for the most part). Summit has some kits for under $1000 and did a 1991 GM TBI on my 63 nova before I sold it. I just got a old Chevy van with TBI for $300 and pulled the TBI and wire harness out and made a plate for the intake. Work well, but it was OBD 1 so had to make my own chips Chrysler TBI is the same thing looked in to it. Of course you will need a bigger fuel pump, return fuel line and update the old fuel line in for the high PSI pump (Jegs sells a nice kit).I cant tell you if my MPG went up because I never drove the car before, but it was nice to have it start on a cold day, take a drive in the hills, or have a little nitrous and know the ECM would keep my Air/ Fuel steady.

With my 440 and 3.23 I get 12 mpg on the hwy. That is with going through small towns and rolling hills.

When calculating fuel mileage, always factor in WORF.
(weight of right foot)

Lol Well I mentioned that above. I know to most people with a 440 gas mileage doesnt matter much and they like to keep their right foot pretty damn heavy when they do drive them. But like I said this is going to be my daily driver, so yeah its gonna matter big time. I just want to do a proper R/T clone with it, and I don't think any R/T ever came with a small block lol. If anyone knows what kind of gas mileage a fuel injected 440 gets that would be helpful as well.

79 -

I'm gonna "guess" about 6-8 mpg combined on mine, but probably less. Definitely less if I even think about "getting on it". (Did seem better in the old days.)

440, mild cam and head work, 850 DP, 3000 stall (yeah that matters), 3.23 gears in a 4200 lb package.

These days, unless you have a lot of expend able cash, prolly not a great idea as a daily driver. Yes it's being done, but not on my budget...

Archer

i get 13 mpg
might get a little better once the speedometer gets working
if you add an efi set up, you'd probably add 2-3 mpg, that is if it has the ability to lean itself out a little when coasting (that set up may require aluminum heads)

my dad claimed he got 15 in his half ton. but he changed gears tire sizes and transmissions to do so,
i get 13 with a 727 and gears don't remember what i have? fairly high though

Just figure 12ish if you can keep your foot out of it!! A mild 440 with a 4 speed?Bwahahaha!! Just sayin' :)

I had a '68 Fury 2 door Fasttop with fender skirts, a mild 383 Magnum from a '69 Charger, Edelbrock Torker, Carter AVS, Accel Super Coil, Mallory dual point with a 727 from a '77 CHP car with the factory 11" torque converter, a 3.23 Sure Grip from a '70 Roadrunner, drive shaft from a '76 Sheriff patrol car and a rear sway bar from the same Sheriff's car. From the outside.... the car looked totally bone stock with Magnum 500's and whitewalls.

This car would do 70 mph in low, 102 mph in 2nd (the valves floated at this speed) and the speedo would run right past the 120 mph mark......

If I could keep my foot out of it.... 12 miles per gallon

food for thought....my well tuned 318 only gets 12-15 because its got to lug around a fully weighted b body with a 2.76 rear
a big block wont have to work as hard, but i could be wrong all these other fellas know a whole lot more than me

I was wondering about that myself, I had a friend tellin me that its possible to get better gas mileage with a big block because it doesnt have to work as hard but I didn't know if that was complete b.s. or not lol. It has a 318 in it now, my challenger does as well, and I figure it gets around 12 to 15mpg, 15 being on a really good day and I don't ever open up all 4 barrels lol. I figure it will be worse in the B-Body since it is quite a bit bigger.

dude glad to see you got the car you where dreamin about
id build a big block for a lot of torque on tap, along with 3.23's or so and you should be ok if you drive conservativly, shift at a lower rpm, and keep it in good tune
lookin forward to that r/t clone

I appreciate that, it actually wasn't the exact B-Body I had in mind. I was actually aiming for a 70 super bee. But I wasn't sure. I was setting here looking through tons of pictures of different b-bodies and I got to looking at the 68's and realized they got style, they got class, and nothing beats that ass lmao. I know that was corny, but really the tail panel on a 68 R/T to me is absolutely killer. And I decided that was what I wanted. Anyways it has a 2.76 rear end in it now lol so my gears shouldnt pull my gas mileage down any if I do go with a big block, If anything they maybe too high for it. And if I do go with a big block I'm gonna save up to put a good fuel injection kit on it to help with the gas mileage. And as far as building it I may just do a stock rebuild maybe put an RV cam in it to give it a bit of thump. Go with a K&N filter, put headers and straight 3 inch exhaust to make sure it breaths real easily... then really try to refrain from stepping into her lol.

My 69 charger 383 mag with 3.23 gears got 17/18 on old school gas

12-15 on the highway?
with 2.76 gears i would expect 18-20

I think that my 95,000 mile '68 Fury, the way she sits now, 383 2bbl, Auto, 2.76 with dual Flowmasters is getting in the neighborhood of 15 mpg.

on my 440 there was a carb rated for a 300-350

i noticed nobody mentioned anything about carbs

So do different carbs on a 440 not affect mileage.

i thought it would because of the load...figured a carb rated for a 440 would be an easier load therefore would hve less usage of secondary linkage running



any thoughts??

well, if you starve an engine (give it too small a carb.), you'll actually get worse gas mileage. You'll need to give it more fuel to get moving.

if you give an engine too much fuel (too big a carb.) you'll use more fuel than you need.

they key is the correct size carb. since that depends on the amount of work done to a 440, no one size is correct. Upwards of 700-800 for stockish is good.

sorry about not clarifying, but here in wilmington, our highways are a good 60mph and have stoplights every mile or two, which hurt my highway mileage a little bit. sorry i should have said that in my last post. you are right, i could get 18-20 on a longer run, but i cant say for sure because iv been scrared to bring the car that far out of town to really tell

over here im lucky to have no a stop light every mile!

My 92 jeep i use to have got 16 to 19 mpg with straight six.

That was after a decent air filter(not paper)

i noticed not being lead footed at the intersection helps quite a bit.
Im going to need to learn some new tricks for my truck.

So today, I filled up my 383 Fury, in Woodland, CA and drove home, to the bay area, which ended up being 130 miles.
Mostly freeway, the ride had about 4 passes over some hills and probably averaged 65mph.
14.988 miles per gallon.
Respectable:)

with what rear again?

Well, I haven't checked and I thought it was a 2.76 but, it acts like a 3.23.
I had another Fury, same year, with a 2.76 rear. In that Fury, at 65mph,
the engine changed pitch and it sounded 'happy' for lack of a better word.
I changed the rear gear to a 3.23 and that 'happy' sound came at 60mph with the lower ratio.

Now, I have my second Fury with a 383/727.
This is the first real road trip that I have taken in this Fury and that 'happy' sound comes at 60mph.
I'll check, when it stops raining, and we'll both know!

Here's a "real world" figure from "back in the day." My old 440 sixpack Roadrunner:

70 Roadrunner
440 sixpack SIX PACK REMOVED
Edelbrock intake
Holley 800 DP
Hang on Air
4 speed
Dana 60, 3.54
G-60 x 15 tires
Cyclone headers
Stock mufflers, tail pipes out by rear tires

That car, in the early '70's, would get a solid 13.8 on the highway. I did NOT particularly drive it "carefully" and bear in mind this was normally at 70 mph or so. The engine turned almost exactly 3000 RPM at that speed

I was in the Navy then, and much of the time lived "on base" so had no storage room. I had two of those huge clamshell toolboxes, FULL of tools. I'd guess they weighed at least 60 lbs apiece, and they were normally in the trunk, along with a few other things. I had the car weighed once with the above configuration, 3860 was the figure.

My satellite with a 440 gets 23 MPG at 120 km/h (75 Mph) on the Trans-Canada Highway. I am running a 2.75 rear end though, so due to the tall gears it does suffer in town a little more. But the carb does make a difference. I have the stock Carter TQ 850 cfm, It has a spread bore and that means that when your foot isn't into it, it only passes a little bit of fuel and air, and when you really drive it feeds your RB alot of fuel. I hate the myth about big blocks and bad fuel economy, because yes, the engine is huge, but it has the power to move your vehicle without any exertion. So it goes both ways. The 360 i replaced in mine only got 11 MPG

There are already a lot of responses, but what the heck. My 1965 Dodge Polara has 383 2bbl with 727. It gets up to 15 mpg on the highway. I could probably get a little better if I stayed 55-65 mph. Surprisingly, its not uncommon to be above 10 mpg city, of course when there is decent traffic.