12 mpg sound right for 351 crate?

[rbray]

Hello everyone,

Last weekend I went on a wonderful cruse with the Kentucky Cobra club.
I took the opportunity to calculate my fuel economy because it was one of the longest drives that I have had my car on so far.

The drive was just at 100 miles and I calculated my fuel milage at almost 12mpg and I'm wondering if this sounds about right .
Here are the facts about my setup.

351 ford crate dual plane intake. Advertised at 360 hp at the fly wheel.
holley 650 cfm street avenger vacuum secondary carb.
tremec 3550 5 speed.
ford 8.8 rear with 3.73 gears

the driving was a mostly country roads with a little interstate thrown in.
we never exceeded the speed limit by more that a few miles per hour.

So is 12mpg about right or do I need to have someone do some tuning on my setup?

[Got the Bug]

12 mpg sounds about right. I checked the mileage on my Roush 402 one time and it was in the 11 mpg range.

[Dens]

rbray

I've got about the same setup as you. I have a 3.10 rear, the worst I've seen is about 9mpg and the best is about 13mpg. I don't check it very often, it's to depressing, but then again that's not why I bought it.

Brad

[bobcowan]

I get 14-15mpg at 80mph. I would expect a smaller engine to be more efficient.

427W Dart, Dart heads, huge hydraulic roller cam, 8 stack EFI. Tremec TKO 5 speed, 3.55 gears.

[Excaliber]

14 to 15 mpg is outstanding! 12 aint bad. 351's never did get much better than that, even when there bone stock! Some studies suggest a BIG block (as in cubic inches) turning a lower rpm (think overdrive) is more fuel efficient than a small block.

[Three Peaks]

Those 3.73 gears aren't doing you any favors, milage wise.

[Sharroll Celby]

I can get about 19 MPG straight cruise about 80 MPH with 3.27 gears. Around town I get about 12 MPG, just normal-ish driving.

How QUICKLY did you accelerate up to those limits?

What is your cruise RPM at, say, 70 MPH? 80 MPH?

Three Peaks is right with the 3.73 comment.

[PANAVIA]

not a fan of the avenger carb for millage. 3.08 gears and a holley 80783C might do better.

[Tinker51]

Stroked to 396 with a tremec 3550 and 3:73's at the back. Dyno says just under 500 hp/tq. I get 10-12 around town but if I take an all freeway run it will get a solid 20.

[Bugman]

I'm running an FE block stroked to 452 with about 530hp through a 3:31 rear. I've never checked my mpg but my spg is waayy up there! (smiles per gallon)

[letsboogie351]

In all my years running a 351C in two Aussie 2 door Falcon Hardtops (heavy vehicles) I never had worse than 13 - 14 mpg around town. On a run regularly saw between 19 - 22 mpg depending on how hard I peddalled. bOn one occasion I achieved 26 mpg on a long distance run

[wtm442]

My 351W has 10.2 to 1 compression ratio and a little over 400 HP at crank. On a 600 mile trip of mostly highway driving, I got 22 MPG. That's with a 3:73 rear end gears and a 0.68 fifth gear ratio.

Of course, around town, the mileage can be anywhere from 12 to 16 MPG depending on the weight of my right foot.

[RANDY CARTER]

That mileage sounds really low to me. I have a 351W crate motor (375HP) with the Tremec transmission and can get about 20 mpg on the highway cruising. I changed the gear from the 3:73 to a 3:31 and the mileage changed significantly for the better. I would suggest looking into a gear change if you are basically a cruiser and not a hard core racer.

[Bob In Ct]

Roger:
I've got a 351 with a dual plane, the same Tremec, the same 3.73 and a Holley 850 and I would get 18 to 22 on a trip like that assuming I was just cruising and not leaning on it a lot. 1,900 RPM at 60 MPH.

Bob

[madmaxx]

I have a roush 427sr/tw and get about 12 mpg around town. I am still in break so I have been driving very conservative. I imagine I will be closer to 10 mpg when I start to take advantage of the power. I have 3.42 with TKO600

[Kzof]

My 390FE, mild build with 3:73s is right there. Same, 12mpg Hwy.

[Got the Bug]

Madmaxx - Superformance is showing a rear-end ratio of 3:46 on their spec sheet for new cars. Guessing that you also went with the .82 OD which keeps the revs up a bit at hwy speed. I'll have to check my freeway mileage sometime since the 11-12 mpg (the only time I checked the mpg) that I got was mostly touring through the hills.

[FOMOCONUT]

430 hp TKO 5 speed 3.43's 65mph 1900 rpm's Ford motorsport 392 670 holley and a dynatune.18.6-22.5 mpg. Was 24 mpg but they gave it more fuel on the dyno.Oh Victor man. which is not the best , some day I will go with injection.12 with a 360 hp on a freeway drive, you are hurting the motor.To much fuel.#2773 Jerry

[Bxx1]

Originally Posted by Tinker51

Stroked to 396 with a tremec 3550 and 3:73's at the back. Dyno says just under 500 hp/tq. I get 10-12 around town but if I take an all freeway run it will get a solid 20.

yeap, thats about what I get too. Except I never got 20mpg on the freeway.

[madmaxx]

Got the bug,

You are right I have the stock 3.46 in my spf with the .82OD