Gas Mileage Roush 427R - just curious

cobrasnake · #1 (**permalink**) 10-03-2007, 09:17 PM

Yes I know we didn't buy these cars with a concern for gas mileage but I was interested in what other owners of Roush 427R's are getting. I have a Holley 870, dual plane manifold, Roush oval air cleaner 427R and get somewhere between 8 and 10 mpg and on a really good day up to 12. Is this consistent with your car? Have you changed your carb or done anything that would change the mileage?

While always interested in what other motors produce, it would be great if you could confine comments to the 427R - yea, I know, rag, rag, rag!

Just the facts, maam.

SPF1061 · #2 (**permalink**) 10-03-2007, 10:10 PM

427R, dual plane, AED custom Holley mechanical double pumper (@850cfm). 10mpg around town or on the highway,
doesn't matter, doesn't get above 10. Get's about 5mpg at VIR.

Rwillia4 · #3 (**permalink**) 10-03-2007, 10:44 PM

I have a keith craft 427w with fuel injection and get about the same ~10ish. I lean it out in cruise 16:1 where I'm upto the high teens. Getting one it (where I usually am

) and it is low single digits. Average ~10ish.

I would much rather be paying for the high cost of gas during the 70's gas crunch!!

scootter · #4 (**permalink**) 10-03-2007, 11:04 PM

Tom,

Sorry, I get better mileage with my 514

. I was getting a couple of gallons less at the gas station's then the smaller engined cars. No names mentioned Chris or Mike!

Scott

Rwillia4 · #5 (**permalink**) 10-03-2007, 11:11 PM

Were the smaller engine cars all filled up by the time you got there.

Mike Bartlett · #6 (**permalink**) 10-03-2007, 11:21 PM

Scott,

So it would seem to be true but then again you can't go past a 1/2 tank so I don't think the math works the same?

Tom,

I know mine isn't the 427R but I get 10-12mpg on trips. I would get a new motor if I was you. Hey a Cobra Hybrid that would be different.

Mike

SPF2245 · #7 (**permalink**) 10-04-2007, 02:05 AM

I can average 10-12 on the highway but nothing I do get's me above 8 in mixed driving. Oh well, atleast the gas never sits long enough to go bad. I've had the carb adjusted, but I really don't think a carb'd 427 is ever going to put out much over 14mpg.

-Dan

RICK LAKE · #8 (**permalink**) 10-04-2007, 06:18 AM

cobrasnake How heavy is your right FOOT??

It's not a honda.

Racing I get about 4-5 gpm. cruising in overdrive with 3.31 gears 14-16 gpm. This is with a very streetable FE motor with FI system. It runs on reg gas if needed. If you put an egg under the gas pedal,

this should help raise the mpg's if not at least you have breakfast.

Rick L.

fsstnotch · #9 (**permalink**) 10-04-2007, 06:34 AM

Rick, you get 14-16 GPM?!

CobraDan · #10 (**permalink**) 10-04-2007, 06:39 AM

My gas mileage on my daily driver, a Trailblazer SS with a Corvette engine says when I initiate the mileage reminder at 14 and it doesn’t matter how I drive it, it has never indicated more than 14. On a long trip I kept all the gas receipts and when I returned home found out I’m actually around 17 miles per gallon. I think sometime the Cobras mileage might be better but it being my toy I have never checked its mileage.

Jerry Clayton · #11 (**permalink**) 10-04-2007, 07:26 AM

There are several things that are effecting your milage besides whether you drive with a lead foot or an egg under the pedal---restrictive small aircleaners ,exhaust systems that have the wrong tuned length, radical high rpm cams that are lugged around below there operating range, carbs and ignition that are dyno tuned for the big number----
That 5-600 hp dyno slip will give you 5-6 mpg---always has(406fe1962) up thru todays versions of similar engines---
If you want mpg get a modern set up with 300-350 inches and enjoy the DRIVE----if you to enjoy the RIDE ( yea, typical Cobra) throw in about $50 every 75 or 80 miles---

Jerry

Hal Copple · #12 (**permalink**) 10-04-2007, 05:16 PM

can't say about mpg and the Roush motors. But in my own car, a 392 Windsor, with 15 inch wheels, several different Tremec and varying diff ratios, i find my highway cruise, at about 70-80 mph, to be around 14-15 mpg at best. In mostly town, perhaps 10-12 or so. Once, had to drive a long distance on a fresh tank, in pouring rain, and due to the risk of hydraplane, and not having much vision, driving very cautiously at about 50 mph for several hundred miles, i was suprised to get 21 mpg!.

Before you do your own mpg test, be sure your speedo-odo is accurate!! I can pull a safe 200+ miles out of a tank of 93 octane. My bladder can't do that, though.

all the best,

Silverback51 · #13 (**permalink**) 10-04-2007, 07:05 PM

Don't know. Don't care.

I do however average about 50 smiles per mile.

RICK LAKE · #14 (**permalink**) 10-05-2007, 05:47 AM

fsstnotch Gald to see you are staying sharp with the gpms

Fire up the motor in an hour. If it runs for 20 minutes without problems. I change the oil and run it to the dyno shop. Have to wait till the people go to work.

Even with street pipes, it still rocks the house

Hope you and family are doing well. Having a heat wave again. In the 80's till Sunday. This is crazy for OCT. Listen to the guy on your shoulder and stay sharp. I leave for R&G on MON morn. Will e-mail before I go. Put 6-spd back in car and fixed shifter. New motor will bounce off 6k rev chip in MSD. Hoping for another 40-60 hp and about 75-80ft of TORQUE

I will be passing through on 80W. You want me to clean the gutters on the house?

. 17 hour drive to Gateway, with 1 power nap. Rick L.