fuel mileage
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 952
Likes: 0
From: Morgantown,WV USA
fuel mileage
I know that it does not really matter, but what kind of fuel mileage are you stock- engined small block guys getting? I did a 129 mile interstate drive today and got 13.3.
Just wondering....
Dan
Just wondering....
Dan
Le Mans Master
Joined: Aug 2006
Posts: 7,413
Likes: 1,552
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Don't even ask!!!
This year with the tops off 12.2
With the tops on and A/C on about 13.8
There was a post about changing the carb base gasket from one big hole to the four hole type and that might get 1 or 2 MPG more. Anyone ever try it?
With the tops on and A/C on about 13.8
There was a post about changing the carb base gasket from one big hole to the four hole type and that might get 1 or 2 MPG more. Anyone ever try it?
Race Director
Joined: Jun 2000
Posts: 10,036
Likes: 667
From: FL
Stock L-48, 4 speed, 3.36 gears - 15 mpg
L-48 with headers, free flow exhaust, 4 speed, 3.36 gears - 18/19 mpg
Built 355, 216 roller cam, 5 speed Tremec, 3.36 gear - 19/20 mpg
All with Quadrajet. Freeing up the exhaust has a big effect on 1970's smog motors.
L-48 with headers, free flow exhaust, 4 speed, 3.36 gears - 18/19 mpg
Built 355, 216 roller cam, 5 speed Tremec, 3.36 gear - 19/20 mpg
All with Quadrajet. Freeing up the exhaust has a big effect on 1970's smog motors.
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Melting Slicks
Joined: Jul 2010
Posts: 2,759
Likes: 820
From: SUFFIELD CT USA 2023 C8 CORVETTE UN-MODIFIED FINALIST
2023 C8 of the Year Finalist - Unmodified
Stock '77 350 5 speed 15.7 MPG. Stock except Flowmaster exhaust, did not accurately check mileage before Flowmasters.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
before i swapped everything on my 77 on a highway i got high 14s or so around town it was about 10-11. it was not very good. and it quickly made it apparent i needed an O/D transmission.....
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,114
From: Crossville TN
You didn't mention what year car you had...but I checked your info and see that you have a '78 car. With a non-computerized engine management system, you should get around 13-15 in light city driving and 16-18 on the highway. Overall I get right at 15.0 mpg for combination of city/highway mileage. The differences between cars is primarily due to carb and engine setup/tune and personal driving habits. There are differences between carbs such that one can be tuned to be more fuel efficient while an identical carb from another vehicle might never be that efficient. Computerized fuel management systems were a BIG improvement over carburetion.
If you are getting 13 mpg during highway driving, you may be able to do better with a change in carb setup and timing changes....unless you have a 3.55 or lower gear ratio in the rear axle. In that case, 13 mpg is about what you can expect. If you do a lot of highway driving, you may want to consider a change to an overdrive transmission.
If you are getting 13 mpg during highway driving, you may be able to do better with a change in carb setup and timing changes....unless you have a 3.55 or lower gear ratio in the rear axle. In that case, 13 mpg is about what you can expect. If you do a lot of highway driving, you may want to consider a change to an overdrive transmission.
Drifting
Joined: Mar 2001
Posts: 1,395
Likes: 6
From: Indiana
Since doing some serious tuning with a wide-band afr setup (LM-2), I'm now getting 10-11 city/ 17.5 hwy. Before tuning, it was 8 city/13.5 hwy. This is on a 300+rwhp 355 with 750dp, 3.36 rear, and no overdrive. Driving style has a lot to do with mileage, and I'm sure anyone other than me could get much better mileage with my cars. FWIW, my 05 GTO is advertised as 17city and I get anywhere from 11-13 max. :o
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Since doing some serious tuning with a wide-band afr setup (LM-2), I'm now getting 10-11 city/ 17.5 hwy. Before tuning, it was 8 city/13.5 hwy. This is on a 300+rwhp 355 with 750dp, 3.36 rear, and no overdrive. Driving style has a lot to do with mileage, and I'm sure anyone other than me could get much better mileage with my cars. FWIW, my 05 GTO is advertised as 17city and I get anywhere from 11-13 max. :o
Le Mans Master
Joined: Oct 2007
Posts: 7,431
Likes: 958
From: Tennessee/Rhode Island
78 L-82 4 speed-3.70 gears-no emissions at all, McJack's shorty headers, 2.5 true duals, and Monza turbo mufflers-around 15 MPG at a steady 70 MPH, 3,500 RPM. The crossfire is better but not that much better. Most of the gain is from the 700R4 overdrive and the lower numerical gear. My buddies 82 crossfire gets about 19-20 on the highway at a steady 70 MPH. I bet with a 5 speed on my L-82 with a steep overdrive (turning 2,000-2,200 RPM at 70 mph), I could easily get 18 MPG at a steady 70 MPG even with 3.70 gears! The gas mileage really did not improve drastically until the tuned port injected engines. My 2010 Z06 with 505 HP gets around 25-26 MPG at 75-80 MPH. I have gotten as high as 27.5 MPG with the Z at a steady 65-70 and being really easy on the gas-pretty unbelieveable!!!!
Last edited by jb78L-82; Aug 24, 2010 at 09:22 AM.
Drifting
Joined: Aug 2009
Posts: 1,635
Likes: 8
From: Enid Oklahoma
In town I get about 16, on the highway about 20 or a little better. I have the L81 motor with the computer stuff removed, and a vacuum dist and regular carb. and true dauls with headers and 2.5 inch exhaust. The super low tech computer system in my opinion was junk and served no real purpose for ME so I put it in a box. I have not regretted it.
