454 MPG Expectations?

[Hook]

Recently got a 78 Suburban and am going to be making a roadtrip fro SoCal to Wichita, Kansas. What can I realistically expect for mileage?
It's a 2500 with a TH400 and a stock 454.

[zieg85]

If the carb it right you could get as much as 10 assuming you have a 3.73 rear gear which normally came std. with the 454 TH400.  Good luck

[BigTree]

Hate to thread-jack a bit here but I have a question about fuel consumption and my 454 as well.

To an 82L tank, I barely get 150kms.

This truck is lifted with 38.5 swampers and some other good stuff, but most of these 150kms are certainly NOT open throttle and the such.  Lots of just 1-2000 rpm driving through town and mud holes.  Is this normal?

Thanks.

**EDIT** that is about 3.9 mpg.

[Captkaos]

4mpg I wouldn't say that is normal.  Was it regeared when you went to the larger tires?

[VileZambonie]

less than 4 mpg you have serious issues!

Original post* Best way to tell is to tune it up and clock it. No 2 trucks are gonna get the same mileage results. Way too many variables

[1badgmc]

My '88 cc dually came factory with a 454/TH400 and 4.10 rear gear. It was a solid 6 mpg from the day it was bought new. A few years ago my dad swapped in a 5-speed stick (after going through 3 transmissions in less than 75,000 miles). I haven't checked it myself yet, but I think he said it's up to around 8 or 9 mpg now. Woohoo!!

[ccz145a]

I have a fairly stock '75 LWB half ton 454. My signature says it all.

[Captkaos]

I have this 454 that that I built back in 1992, it is going to be converted to EFI (Hilborn style)
This is when I first got it running:

This is what it looks like today:


When it was running with, well, a HUGE cam, closed chambers and a 800 Holley with a stick shift and 3.42 gears and 28" tall tires it would get 12mpg when my foot wasn't in it.

[BigTree]

Captkaos - I am now jelous and going to go cry at the sight of that.


I do believe the truck now has 4.56 gears, or something very close to that.

It does have a cam and edelbrock intake + Carb. 

Any ideas guys?

Thanks a ton.

[VileZambonie]

My 454 is built and if I drive it easy I get somewhere around 12 also

[Leadfoot]

I had a crewcab dually,bone stock quadrajet 454,th400 and 4.10's.. it got 6 mpg..the good news is the mileage didn't drop much when pulling..

[Captkaos]

Captkaos - I am now jelous and going to go cry at the sight of that.

Sorry about that.  It is a work in progress...

82L with 150km is like 1.8km/L with = 4.42mpg, still a little low but those are some HUGE tires for the street.
What kind of cam?  What kind of carb?  how is the tune of the motor?  I would think you should get at least 6-8mpg out of it.

[SUX2BU99]

I realize a BBC is an inherently fuel-ineffiicent motor and single digit numbers were common in the 60s. But after 20-30+ years of technology and innovation, GM couldn't get any BETTER numbers, while pulling down LESS power numbers? An 88 454 is a pretty weak motor, powerwise.  Wonder if the window stickers actually showed single digits for EPA mileage.

[1badgmc]

These trucks were exempt from EPA fuel mileage requirements, so the window stickers were blank there. Trust me. I still have the sticker for my '88.