nassau66427

Has anyone calculated their mileage? Mine seems to be somewhere between bad and poor. What kind of numbers might I expect if I am brave enough to actually figure it out? I'm running a Tri-power 454 and 4 speed. EFI and OD tranny guys feel free to boast.

67's

I would say you are probably in the 13 to 14 range, could be worse you could only have one carb, then you would probably be in the 8 to 9 range.

Tom M

67-427ci

I checked my mileage a few weeks ago. It is 13.7 on the highway. My engine is a 454/425hp HO GM Crate engine with the L71 Tri-power. M21 4spd with 370:1 rear end.
Roy

66BB

My 66, 427/390 runs 12 city and 14.4 highway on unleaded premium. Now if I could only figure out how to keep my foot out of it, I might acutally squeeze an extra mpg out of it,,,,,,not.

67435animal

On my 435 I used to get 17-18 highway until I hit the throttle hard. Then it would get around 8.

427/435 M21 4:11 gears....what a blast!

midyear

My yellow 67 has a mild well tuned 400hp 427 w/a 700R4 trans and 3.55 gears. best ever was 22.1 with AC on top up coming back from carlisle. I caravan with a buddy in a 66 390hp coupe M20 and 3.08 gears. He usualy gets between 17 and 19 depending on how fast we are traveling.

Dennis

MidYearRoadster

My 390 hp which has a mild comp cam and larger than stock holley, with 336's and 215x75x15's gets 17plus on a highway cruise at about 70mph....i never checked city driving....why bother.

StrayDog

My 1966 ,427 cu in single 4 bbl "Used to get" 15 MPG on trips when I had the 3.08 rear gears..........now have 3.70 gears & in the 11/12 mpg city MPG range At best ..... the double pumper Holley contributes to this, but its the price you pay for the E-Ticket ride.....food for thought>>>> used to drive the 66 , 1,200 miles a season.but with $2.55 high test , no more HWY cruisin.......this may be OK for the NCRS guys who spend all day waxin & shinin & only drive to shows & sayin my Corvette is perfect ,,,,but for me that likes aceleration & drives hard ........WOE, thoughts & 2 cents from the Dog

magicv8

IMO Bunch of optomists on this site

My experience, 454 (bored .03) BB in suburbia with 4.56 gears 6mpg.

Switched to a 350 SB and 3.36 gears to get 14.5 on the highway (65mph average speed on trips cruising about 73mph using cruise control)

Switched to 3.08 gears for 19mpg. Added an air dam for 20mpg. (same average trip speed )

dknowles67

Hard to say with a non-functioning fuel gauge, and broken odometer.

But I wondered the same thing.
So I kept a log for one tankful.
Went back over all the routes I took with another vehicle, and recorded the mileage.
I've removed the original carb, and replaced it with a newer Holley 750 cfm (that doesn't leak so bad, and is easier to adjust) before this test.
With the 3.36 rear end, my 427/390 seems to get about 8mpg.
(All city, few stop lights, pedal to the floor until the tires spin acceleration at at least a few stops).
After talking to some people who drove these in the '60's and '70's they don't seem to think that's too unusual.
12mpg would be good for these engines.

centric

Sounds right on to me. 427/425/3.36 here, near stock, maybe 9-10 in town, 14-15 on the highway for long trips.

67L36Driver

"Big block MPG?"
Sucks, even with my QJet setup (tiny primaries).
They'r not too good on oil consumption either. Guide seals?

All you have to do is put your foot in it and you forget about economy.

When I had a plain vanilla 327 in my vet I used to get 21-23 mpg on the hiway with a spreadbore.

hermit

468 with 4.56 gears. 4.5 mpg the last time I checked.

MassVette

I have a Tri- Power 454 with ROD 6 speed in my 67 roadster, with 3:70 gears. My avg. MPG = 9-12

Dad's '66

427/425 with 4.11's. Going down the freeway at 70-75, I swear you can see the gauge move........

DansYellow66

66 Coupe with a pieced together, mostly L-88 motor and 4.11:1 rear - I get a pretty much steady 7 mpg running around town and nearby country roads. Worse is my completely stock 1967 440 Plymouth GTX which also gets only 7 mpg with 3.23:1 rear.

srthom

427/425 with 4:11 gears. At best 10 mpg.

67-427ci

Just did a 500 mile check with a combination of freeway & country driving, nothing over 70 mph. My average is 13.6. That's as good as it gets (454/435hp, L71 Tri-Power, 3.70:1 gears, M21 tranny).

INMYBLOOD

and see the persian gulf doing the wave. You guys are driving BB corvettes..... what's not to like.

Russ T Gate

67 coupe, 4 speed, 3:36 gears, 427 single 4 10 mpg. with a injected 502 and everything else the same 15 mpg.