What kind of gas mileage are you big-block guys getting with pump premium?

Chef AR

 

About 7 mpg with 4.11:1 gears and puttering around town and country roads. My stock 67 GTX 440/auto/3.23 gets about the same. Even my Lightning pickup is down to about 10 or 11 mpg lately. I seem to be mileage challenged.

 

67-390, 15.5-16 mpg, 3:36 gears.

 

10-11 on 87 octane. 3.36 rear gears and truck heads.

 

67 Coupe, zz454, 440hp Crate Engine, Tremec TKO-600, 3.70 gears. On my drive to Bloomington Gold from NY averaged 17.8 MPG.
Roy

 

396 with 4:11 rear 8mpg, last time I drove it 15 years ago

 

It's all in the gearing. A buddy has a mild 540 that gets 18.9 mpg with 3.08's and a TKO.

Another has a 454 with aluminum heads and Holley EFI that gets nearly 22 when driven nice with same gearing as above.

Mine gets about 12 with 3.07's, no O/D. But my cam is a little healthy and I have a 1050 Dominator carb.

That's going to be a nice future project to tune it to 15+mpg. I really don't think it will be that hard to do.

JIM

 

7-8 with the Yellow L88 driving into a 4.11 gear. One of the reasons it was parked in 1973 and for it`s corect mileage of 28086. But I also had 2 other Vettes sharing my driving mileage accumulation

 

I have a .060 over 427 with L-88 heads and a 292 Comp Cam. The driveline is a Richmond 5 speed (no O/D) and 3.54 Dana 60 rear. I get 7-8 mpg driving normally If I drive very carefully I can get 14-15 but then it's no fun.

I guess if I really cared about mileage I'd probably be driving something else. If you want to play you have to pay.

Bob

 

I can honestly say that I've never, ever checked my mileage on the Vette. I put a 5 speed in her, not for mileage improvement, but for idling her down on the highway, hopefully prolonging engine life and lowering the engine noise at speed.

Now I do periodically check mileage on my daily drivers.

- Pat

 

My guess would be about 8-10 with a 468 4sp and 3.73 gear. It is fun and I dont really care as long as i dont run out before I get home

 

My guess would be 8-12+ MPG in my '65 Vert, burning 91 Octane, & running a 400cid small block, w/3:36 gear. (Now, realize that 12+ MPG higher range happens only if I'm driving downhill at 50MPH in 4th gear with a strong wind at my back, and with no previous acceleration display bursts.)

As stated earlier, MPG is not even a consideration when the top is down, the weather is nice, and there's a need for speed.

 

Mild 427, M21, 3:36 Rear. 8-11 around town, 14 highway. Injected 502 530 hp M21, 3:36 rear, high of 17 mpg. Same setup with TKO 600, high of 21 mpg and the ability to hear at highway speeds,
Russ

 

i wonder if the guys that don't check, r themselves obese?
Just shovel in the ice cream? Never step on scale?
.
Decades ago, when cars had points, mpg gave an early clue that something was amis.
Low mpg means u have to plan gas stops carefully on the interstate or run out- no matter how rich u r. not checking mpg says to me u don't care if your engine is ruined from gas washing the rings, which to me says u r not a car guy, just a rich guy with a toy.

 

Hydro-cammed L72, 3:55s, M21. Fun - 10-12 mpg. Long road trip @3000-3200 rpm - 13-14 mpg.

A freekin' economy ride!!

Jeff

 

Then for one of the very few times, I guess that you'd be wrong on all counts Matt!

I've been a car guy all my life, am trim, am not a rich guy, never checked mileage in my 'specialty' cars and never lost an engine. How many have you lost? Maybe you've spent too much time checking your fuel mileage and not enough listening, looking and smelling.



- Pat

 

Yeah, I don't know what is actually in there because the tranny has been replaced, but I'm getting about 7 mpg with the 427/390. I just wondered what was considered normal. Thanks to all.

 

Hey, I ain't fat and I'm sure not rich but I'll bet you I know how my car is running without seeing how many gallons of gas I'm burning. Gas prices are depressing enough without constantly reminding myself of how much I'm using. I only have an 8 gallon tank so I get reminded enough as it is.

Bob

 

I don't mind being wrong. In the 70's i "lost" 2 cars because of poor mpg. Both 6cyl that got 11! '65 comet and a '65 corvair turbo. Sold them and bought my 61 with the money.
i have a 2 gal tank in my 61, so i've taken a new interest in mpg, since it is so easy to check(i've marked it every 0.2 gal). Fun! I learned the 1st 2 minutes really suck gas, and that fully warm idle used 2.1 gph! So, no, i'm not smart enough to know this without doing a test.
A dozen things can give poor mpg. This 1 took 13 years to track down; YES IT WAS WORTH IT http://community.webtv.net/MATTGRU/carb

 

This is going to be more of a "tip" to the "planned" builds as opposed to the "running" units!

We've been building these powerplants for some time now and have never worried about "economy" in the past. Well times have changed some and many of my own guys are looking to save a few bucks now.

I have no issues with this fact and we plan on some future testing, but it will most likely be next year due to the present workload!

First, whether it's a SB or a BB planned, get the longest "arm" (stroke) as you can possibly fit in the program and keep the bores as small as possible without sacrificing too much power.

Most acceptible build's today are the 3.750" stroke 4.000" bore SB's (383") and the 4.250" stroke 4.250"/4.310" BB's (482"/496").

The 383" is still the best choice here (SB's), but now we are going up to the 4.375" stroke on the 454" platform. The cranks go in with a minimum of grinding. The longer stroke increases the "Torque" numbers greatly, and allows the use of much lower rear-gear numbers.

It may not seem much, but we feel we can help the overall "consumption" to the tune of some 20%/30% or so. This is from the build itself, NOT the peripherals, like the trans, weight, etc! O.D.'s are definitely "in" now. "Injection" would be next on the list.

This is NOT for the "race-oriented" guy's, more for the "cruiser's" and the usually greater "seat-of-the-pants" feeling guy's!

With respect to the BB's (454's), you will still have a "serious" 504"/510" economy build. We also have planned a number of 4.500" bores with the 4.375" strokes, yielding some 556"/572" short-decks!

Thanks, Gary in N.Y.

P.S. This "thinking" is pretty much along the lines of G.M.'s own, with respect to the introduction of the 305" years ago! G.M maintained the 3.480" stroke and introduced the 3.736" bores. These 305's were offered in many performance app's, including the Camaro's and Monte's.