How bad is your gas mileage?

[tmareina]

Didn't put the BEAST together for it's great gas mileage!!! HOWEVER...with 614 HP and .64 final fifth gear on the highway with a sane peddal I can get 12MPG usually 9-10 in town without the foot in it. When it gets on the track...all bets are off...at best 5MPG...BUT man does it RUN.

TOM

[Streetwize]

I have a 427 Windsor at 10:1 with with ported Trick flows that flow 252 @.400 and just over 280 @.500. with a .68 o/d tremec and 3.50 gears and 305/50-R15 tires it turns about 1800 @ 65mph but still has PLENTY of roll-on torque. I'm getting right at 21 mpg on the highway in od but if I run it like a 4 speed 1:1 4th it would drop to maybe 14.

Picking the right cam makes all the difference in the world, if you got great heads on the motor you don't need too big a cam and still make great power and very broad torque, an overcammed or under-compressed motor can pull a light Cobra below 2000 RPM but it's not always in a good efficiency zone for part throttle MPG efficiency. Intake port cross section and vacuum make a huge difference too.

[mdross1]

All of things I would have suggested have been said.It really boils down to how much it really means to you.In my case with 525 hp,468,fed with an 850 dbl pmp,I changed out rear gear from 3.54 to 3.70,and a top loader to Tremec TKO,and took what I got.My concern was cruising at 80mph and getting the rpm's down so it would be liveable,inside the car.It worked! Good Luck

[Full Throttle Al]

SOHC with Webers, 3mpg no matter what.



Alan Sorkey
Shreveport, LA
CSX4083

[elmariachi]

Man, that SOHC with Webers is the baddest of the bad when it comes to Cobra engines.

My side oiler is 9.8:1 compression, 93 octane pump gas, medium riser heads, Sidewinder intake, 750Mighty Demon and a lumpy 294S cam. I have the TKO 600 with .64 OD and a 3.50 rear axle. I am getting about 7mpg running around town and 9-10 on the highway. I am sure I could get 12-14 on an Interstate trip with that tall 5th, but I have to be breaking the speed of sound to use it.

[ken swart]

full throttle al is the coolest

[67FEfastback]

Originally Posted by Full Throttle Al

SOHC with Webers, 3mpg no matter what.



Alan Sorkey
Shreveport, LA
CSX4083

That is NICE. I'm sure that you can easily get some willing volunteers to drive a gas truck behind you

[Moriarty]

I was looking at my gas mileage and noticed that the two times I got gas from a 76 station, my mileage was worse (5-6 vs 7-8 normally.. this was before I tuned my carb). This was 92 octane, and I usually fill up with Shell V-Power 92 unless the station only has 91. Two data points isn't much to go on, so I figured I'd ask and see if anyone else has noticed lower gas mileage based on where they fill up?

I also had done some experimenting with the Spirit station nearby which has no-ethanol gasoline but only at 89 octane (both straight and mixed with various octane boosters and leaded race gas). Mostly that all continued in the 7-8 mpg range, which also made the two tanks of 76 stand out to me.

Any ideas why that might be?

[Dwight]

this thread was started in 2008. Twelve years later it's still going.


I copied this from one of my other post but added a few comments.
+++++++++++++++++++++++++

Ok I'm going to give you the short story

A few years back I installed a dyno-ed 530 hp 408 in a Cobra for Mike. He drove it 130 miles home and called me about the gas mileage. 6.7 MPG.
I told him to bring it back and I would let Coach tune the carb. (Coach is my carb guy. I like EFI.)
We called the shop (Keith Craft )that had build the motor and they told us they only tune for wide open throttle because they did not know what air filter, alternator, headers, exhausts system, etc that we would use.

Mike brought the car back and Coach tuned the carb. Trip back home he got about 13 mpg.
The next year I drove it to the London Cobra Show. Round trip 1150 miles and I got 16.7 or 17. something, don't remember for sure.
Moral of the story is check the power valve and get the carb. tuned. There is more to tuning than adjusting the idle screw. Jet size, air fuel ratio, cam plays a big part.

Air Filter is a big issue on fuel consumption.
I had a 351 W one time that would not rev over 4300 rpms in any gear. Stopped on the side of the road and removed the 8" air filter and the motor would rev to 6,000 in any gear.

[desgros@vtlink.]

All big block motors, high HP. All good! Now for my Slabside 289 HiPo. The best MPG I get is 12-15. So I guess what the big motors get is not that bad given the return in brute speed and power.
Always a trade off for nearly everything.

John
ERA #3010 Slabside 289 SB BRG

[eschaider]

I went one heat range colder on my NGK plugs from a TR6 heat range to a 7 heat range and my mileage cratered. It dropped from just over 27 mpg to essentially 25 mpg! Didn't take long to get back to the older more friendly 6 heat range plugs.


Ed

[TLHanna]

My 485 hp 427w got between 8-10 mpg. Going to Inglese 8 stack with FAST EFI 2.0 and FAST distributor bumped me up to 12-15 mpg. Eye candy and better gas mileage !?!? Works for me.

[Bricklayer]

427 s.o. 550 HP, 3:54 rear, Toploader, real magnesium Halibrands, aluminum interior, doors, hood, firewall, rear bulkhead, trunk interior & trunk lid & floors. Medium riser w/Holley 750. It's plenty light but still only get 7-9 mpg around town.

[1985 CCX]

My MKIV get about 22-24 mpg which is nice as the Gold car gets 6mpg.

[desgros@vtlink.]

Years ago I owned a Lone Star with a 302 SB/ 5 speed trans. Just a crate motor. 20 plus mpg was normal.

John
ERA #3010 Slabside 289 SB BRG

[tonywyso]

First stop every time out the gas station.

[peterpjb]

'64 289 Hipo engine built to FIA specs with Weber 48IDA, 415 hp at the wheels

7-8 mpg....

[xb-60]

Originally Posted by 1985 CCX

....the Gold car gets 6mpg.

6mpg??
Ouch!

[peterpjb]

Originally Posted by xb-60

6mpg??
Ouch!

I'm relieved to hear that anyone has a worse gas milage than me

[xb-60]

Well Peter, 20 to 25% better mileage (better than 6mpg) is something to be proud of, yes?

edit: ....but then the US gallon is what? ....17% smaller than the British/Australian gallon? It reduces that 20-25% figure back somewhat
The appearance of the Webers is worth the extra fuel cost


Cheers!
Glen