lodom

I'm vettless for now :sad: and am looking at mid-70's C3's, and I'd like to buy one in a few months, assuming I can find one. What I'd like to know about is the fuel economy of an automatic equipped car with a 454 or a 350 driven in the city? This would be average driving without a heavy foot. Thanks.

Missileman

My 71 bone stock 350 (270 horse, automatic, original cam, points, rochester carb, 3.08 gears) gets 18 mpg on highway and 15mpg city. A dual plane intake, electronic ignition, and adjustable carb would easily get 20mpg. A big block almost cuts these numbers in half.

lodom

Thanks.

I was hoping the big block's mileage wasn't that bad. I guess that's why the 454 was dropped in 75. The small block's numbers look good. I'm just looking at operating costs and don't want to stop at every gas station. I guess if you want to play, you gotta pay.

Alwyn678

Mileage is NOT a consideration :lolg:

71DropTop

mileage? what mileage!!!! My BB gets somewhere around 9MPG even without a heavy foot which is almost never :auto: :auto: :auto:

ZD75blue

The way i understand it... a carbed warmed over sb is doing well at 15 in the city, and 20 on the road...

But a big block fuel consumption is read in cubic feet per minute :jester

zwede

My 454 gets about 11-12 city and 15-16 highway, but I'm fuel injected.

page62

Get yerself a '75 L48 auto with a 2.73 rear end. You'll like the gas mileage! :jester

trw

My BB gets about 10 in town and 14 on the highway.

Terry

lodom

Thanks for the replies. The numbers posted are in the ballpark of what I'd expect. Just needed to hear it from people that own the cars.

Gas mileage isn't the only consideration. I've never owned a big block car and was really just curious. I expect if the right car came along, I wouldn't have a problem with the big block. I know I'd love the power, and the extra resale value it adds to the car.

Larry B.

Mine gets around 9 mpg in town with the A/C on. I think it's worth it in terms of fun per mile. :jester

mayberg

My 454 gives me 7 city 8 highway. I try to shred the tires every chance I get, but that highway mileage means I have to gas up about every time I have to number 1.

Sorry, I'm still hung up on Rick's post.

Corey_68

If you are worried about MPG, then don't even consider the Big Block. :nonod:

Robert N

:lolg: :lolg:

71vettman

With 3.08's and my 454 I get 8 around town if driving easy and Ive gotten up to 13 on the highway!! I would never trade the fun this engine provides for gas mileage :yesnod:

lodom

Thanks everyone for the posts! :cheers: The condition of the car is going to be more of an issue for me than the engine size or gas mileage. Whatever engine it has, it won't remain stock for long :)

Chuck Harmon

I guess I am kind of an odd ball. Yeh, a BB will get less mileage, but it is mostly a direct relation to the amount of horse power used. Same gearing, fresh by the book tune-up, cruising down the highway door handle to door handle, a mild BB (i.e. 390hp) Vette will only get about 2mpg less than a typical SB (i.e. 300hp). It is just too easy and even more fun to use the boat load of torque available with the BB.

The internal friction of a BB is not that much greater than a small block, This is the only difference other than the slight increase in weight (as a percentage of the total vehicle weight) penalizing mileage. A BB doesn't have a different A/F ratio than a SB. Stoichiometric ratio is still 14.7 for both. It requires less than 20 hp to sustain 60 mph on the highway. Even my dad's Cadillac with 472 and QJet would get 18mpg's cruising between Chicago and Denver on I80 at 75-80mph when I was a kid. Unless running 4.11 gears, getting sub 10mpg's during steady cruise on the highway means something is not right. However, taking advantage of the marvelous power band to pass frequently while cruising on the highway will produce very low numbers.

Chuck

AlwaysWave

click it to enlarge. This is a mileage profile I put together from guys right here on C3.


[Modified by biltogo, 12:54 AM 3/1/2003]