Big block vs. small block fuel efficiency?

[MaineShark]

I'm planning on buying a shark, and I was hoping some of the members here could share some experience, to help me make some decisions about year, engine, etc.

1. What kind of gas mileage can I expect from a small block (city and highway)?

2. How about a big block?

3. How much does the cat-equipped exhaust hurt economy, compared to dual exhausts?

4. What is the law regarding exhaust modifications? Maine doesn't have emissions testing, but I've heard everything from "any modification to the intake or exhaust is illegal (but probably won't be prosecuted)" to people naming specific years before which modifications are legal (and everyone seems to have a different year in mind), to "everything older than ___ years is legal to modify" (25 seems to be the most popular).

I know fuel efficiency isn't the most important thing in a sports car, but I want to be able to compare the big block to the small block, and then be able to budget approximately for fuel, so I know how much I have left over to play each year.

Joe

 

[DDLS3]

Joe,
This thread ought to draw some comments so I'll throw in my 2 cents worth. Small block, stock or close to stock, 15-18 mpg depending on how much you like to listen to the secondaries holler(much less if you really like to hear them) Big block, I would think a 2-3 mpg drop would be about all you would see. I just moved out of Maine 2 months ago after having spent 49+ years there, so I can speak to an exhaust/modification issue or two. Presently Maine does not have emisions testing state wide, it will likely come back eventually since it was there once before. If your car had a cat on it, it is supposed to be there at inspection time. Few inspection station operators really enforce this, shop around and you can find one who does not pretty easy. There are without a doubt, thousands of modified vettes and other muscle cars on the road in Maine. As far as I know, "NO ONE" has been prosecuted for any mods period. Occasionaly you may find an inspection station that refuses to issue you an annual state inspection sticker, but that is all you can expect. Less restrictive exhaust systems tend to lean out the fuel mix, add horse power, and improve fuel economy.

 

[JHL]

Hi,

"Efficiency" and "Big Block" don`t go in the same sentence :L

I used to religously check fuel consumption at one time and when I had a fairly standard 80 4spd a few years ago and it averaged 17mpg during the time I owned it. My current 81 is doing around 10 - 12 mpg. In the 80 on a cruise it was doing about 20 if you could keep your foot off the gas and stick to 60mph. Big blocks are another story all together. I have never had a big block Chevy but I have had a few others, a couple of 455 Buicks, a 500 inch Caddy and a 460 Ford in a hot rod to name but a few, fuel consumption was brutal and rarely got into double figures so I imagine a big block Vette won`t be any better.

J.

 

[78SilvAnniv]

How much are you planning on driving?

If you want to use the vette often, I'd opt for better mileage.

If you are only going to take it out once in a while to play, get a BB and play hard, mileage won't matter, just the "smiles per mile"!
Heidi

 

[Tom Bryant]

I think I squeezed about 15.5 out of my 427/390hp once but that was really babying it. What fun is that. A standard small block in good tune will perform as Dale said. Better balanced car too with nearly perfect 50/50 weight distribution. Big blocks are nose heavy and will push big time if you go into a corner too hot. Get the small block for a cruiser/touring car. Also remember that if you buy a '74 or older there is no cat and you have true dual exhaust. Most states use 1974 as the cut off year for enforcing emisions rules too so you can do what you want.

Welcome to the Corvette Action Center and good luck on your Corvette Search.

Tom

 

[MaineShark]

I guess I should have mentioned intended use - this will be a daily driver. I drive a mixture of highway and in-town - mostly highway in the fall, winter, and spring, and mostly in-town in the summer (with all the tourists, even the highways are pretty much the same as in-town driving during the summer).

I'm embarassed to admit that I didn't even consider the balance difference due to the weight of the big block. Since I tend to be more interested in driving on twisty back-country roads, rather than getting arrested for felony speeding on a straight road, I guess the small block would fit my needs better.

I hope I can find a '74 or earlier ('73 with sidepipes is my personal favorite), so I don't have to deal with cats, but I haven't had much luck locating one in good condition, for a reasonable price. Actually, the only ones I've found in good shape are all '77s (and all seem to be L48's instead of L82's).

Joe

 

[DDLS3]

Joe,

A new Uncle Henry's comes out every Thursday. There have been some very good buys on sharks, especially in the fall, when people seem to want to part with their vette instead of storing it. After October passes you will be hard pressed to even see a C5 on Maine roads let alone a C3. Watch the sports car section every week if your serious about finding an early 70's vette. If you don't find what you want this fall, spring usually brings another big purge of sharks too, but don't expect any real bargins. If you want to roam the twists and turns with all the grace a vette has to offer, then get yourself a small block. If you want more power later on build some into that 350. For a few bucks or for big bucks(your choice) you can make some serious horse power with that small block chevy. BTW, you might want to check out the great info here at the CAC. Click on the Model Center tab at the top of the page, you can then select any model year and get info on engine options, quantity built, and rated horsepower. Also the last corvette model year to have a BB was 74, all engine options were SB from 75 on.

 

[MaineShark]

Actually, I found this place because of the Model Center - I was doing an Internet search for specifications for some year (can't remember which one, anymore - it was a few weeks ago), and I stumbled across the Model Center.

I've found a few Sharks in Uncle Henry's, Auto Hunter, etc., but have had poor luck finding early ones that are in good condition (including a few trips down into Mass, to look at cars that were supposedly in 'good condition', only to find some seriously beat-up cars). But I keep looking each week. I may end up buying a '77 for now, and then look for a '73 to tinker with in a few years.

Joe

 

[jmp]

BB fuel efficiency is not always better than SB fuel efficiency. Take my 72 LT-1 for instance. The Motor Trend observed mileage (back in 72) was 9-12 mpg. The observed mileage for the 454 was 13-15 mpg! So, I'd have to say it depends on the BB or SB you plan on buying!