What are you getting for fuel mileage from your 455

I have run 455 cars with 4.78, 3.64, 3.42 , 3.23, and 2.93 gears. If you are going to take any trips the 3.23 is the best all around gear with plenty off the stoplight. (Meaning more than full accelerator will allow)

 

My worst is 12 in the city, my average is 15 and my best 19 on the highway that's in the Riv with 2.93 gears.


And "posi unit" they aren't really "highway" gears, not when you get the kind of torque you can out of a 455. Jim is right on the money. 2.93 might not give you a great take off but anything over 3.42 is too much track not enough cruise.

 

I use 2 gallons per .25 mile. :Brow:

 

GS1 said
I have a Holley spreadbore replacement carb. I don't even
know how big

get the list / model numbers off of the carb and i'll look it up for you. i've got a holley book which seems to list everything.

 

455 MPG

3:42 Is the best over all!!! :Brow: :3gears:

 

My '68 400 got 18-19 mpg on the trip to Salem and back. It really surprised me....

65-70 mph
2.93 posi rear.

:beer

 

Put a 3.08 rear for the trip to BG, much better gas mileage than with the 3.64 rear. The car came out of the hole like a bastard with the 3.64 rear-- I thought-- My quarter mile times were only.05 different!

 

455 MPG

Johnno, the only problem is the 3:08 gears are hard on a drive line with the torque of a health 455, AL.

 

I've gotten just under 20 with my EFI 455 & 2.56 gears. Right now, though, it's usally more like 14-15 MPG because of a bigger cam and poor ring sealing.

Al, what do you mean it is "hard on a driveline"? The 3.08s are a lot easier than the 3.64!

-Bob Cunningham

 

I would think that with out the 2.56 gears, when the power is put down through the trans and driveshaft more energy would return back through them. While with even a 3.08 gear more of that energy would go to the tires. My 2 cents.

 

Bad mileage

I agree... if we wanted good gas mileage we would'nt have muscle cars. Right? That's the whole point. More gas more power! Yeah!
I get 8mpg. with 4:10 rear, th350, and 455 with Holley/750. Rear tires are 255/60r15. 4,200 rpm at 72mph. Future plan is a 700r4 to keep engine rpm's down.
Good post.
Mike

 

On the trip back from Salem the Wagon got 13.3 MPG:Brow:
And thats with the new TSP mill with a q-jet and 3.42's

D.

 

gas mileage? :laugh: :laugh: We don't need no stinkin' gas mileage!
My guess would be usually 8 mpg. with 3:08's. But I can't seem to keep my foot out of it, too much fun!!!

Brian :3gears:

 

Here's a question:

How does ignition timing effect mileage?

 

Well, my 72GS462 with 3.73 gears and a 200 4R calculated at 18 mpg on the way to Salem. I was really happy.

Then I realized that a 460 mile trip clocked on the OD at about 600 miles because we didn't change the speedo gear when we put in the 3.73s and the 200 4R. Of course, I knew the speedo was high because I was centered at around 80 and 2200RPM but not going much faster than most and being passed by a few. A very few, but a few.

Compensating for all that, it's still around 14mpg. Damn good when it's got 3.73s for the launch. I see what you're saying about 3.42s being best but I'm assuming you don't want to bother with slicks. Frankly I prefer a set of race tires rather than burning up the ones I drive around on. And the slicks dig in with the 3.73s.

Overdrive is a wonderful thing when you're on the turnpike.

 

I average 13mpg with my 100k mike '75 455.
2.93 one-legger.

John

 

I get 17mpg on the highway with 2.75 gears, 200-4r, and 2500stall non lockup, in the Regal
I use the Edl 850 rpm Q-jet. T/A stage 1 intake, headers, mild cam. 0-60 4.8

Dean

 

Pardon the pun: Big Time.

Especially if your timing is retarded (late). Would you rather have your burning fuel make cylinder pressure or heat?

The manufacturers put vacuum advance in the equation to enhance mileage at the engine speed where most driving is done.

 

When my 4 spd 455 was stock I averaged about 13 mpg when driving it easy combined city and highway. My best was exactly 20 mpg on an all highway trip 60 mph and trying my hardest to get the best mileage I could. now??????? 10? 8? I haven't checked in years!

That's with 3.42's

 

I recently purchased a '68 Sportwagon with a 350. The first few tanks of gas, I got 11.5 MPG.

Then I started to play with the timing. I played with initial timing, the advance springs, and installed an adjustable vacuum advance.

Now I average about 15 MPG.

It makes a difference!

(This is mostly highway driving, I do about 80 miles/day round trip)

-Bob Cunningham