454 HO gas mileage

[1987_chevy]

I have a 454 HO I am planning on running in my truck. I'm going to be running 3.73s and 33s. Has anyone used this motor in a similar setup? I am wondering about gas mileage.

 

[Jims86]

I have a 454 HO I am planning on running in my truck. I'm going to be running 3.73s and 33s. Has anyone used this motor in a similar setup? I am wondering about gas mileage.

Maybe 13 or so if you keep your foot out of it...maybe better with a custom tune.

 

[1987_chevy]

Maybe 13 or so if you keep your foot out of it...maybe better with a custom tune.

That's what i was thinking, was just wondering if anyone else had this same setup. Gonna be running a Holley 850.

 

[firefighter-emt03]

Im running a 454 with a stock q-jet 3.42s and 33's th400 i get 8mpg im hoping to gear it 4.11 and see if it helps. I was getting 10 with 31 10.50 15. But im also driving a suburban which is heavier than your pickup.

 

[roadtriper]

Im running a 454 with a stock q-jet 3.42s and 33's th400 i get 8mpg im hoping to gear it 4.11 and see if it helps. I was getting 10 with 31 10.50 15. But im also driving a suburban which is heavier than your pickup.

What's you're theory that switching from 3:42 gears to 4:11's is gonna improve fuel millage? I'm thinking just the opposite? RT

 

[firefighter-emt03]

Im runnin 33" tires now so a prime gear swap would be a 3.73 would geat me close to the same as stock tires and 3.42s reason for 4.11 is im gonna run 35s next and prime gear for 35s is like 4.05...thus the 4.11 imo

 

[bucket]

My 2wd 454 Burb can get 13 on the highway and keep up with traffic at the same time. It has 32" basically and 3.73.

I've only been able to calculate mpg on the crew cab dually once, it got 10 mpg. It has 4.56's and tires in the 35"-36" range. Both trucks are th400.

 

[Jims86]

What's you're theory that switching from 3:42 gears to 4:11's is gonna improve fuel millage? I'm thinking just the opposite? RT

The engine is working a lot harder to get the truck moving and keep it there with 3.42's and 33's.
The higher gears will have him shifting sooner, and put the engine closer to its sweet spot. Lower gear less work, but too low, and highway mpg will suffer.
Kinda like finding that perfect gear on a 10 speed bike when peddling into the wind, or going up hill.

 

[roadtriper]

Im runnin 33" tires now so a prime gear swap would be a 3.73 would geat me close to the same as stock tires and 3.42s reason for 4.11 is im gonna run 35s next and prime gear for 35s is like 4.05...thus the 4.11 imo

I see your math and agree with it to try and stay close to the final drive ratio as you started with. BUT

if everything else stayed the same and you switched your truck from 31's to 33's your highway millage should have increased a little, not gone down 2 mpg. 33's have a greater circumference thus for each rotation the truck moves further down the road.
when you put on the 33's did you change the speedo gears? if not your odometer will be counting fewer miles than you are actually traveling thus messing with your MPG calculations you're also traveling at a higher rate of speed than reflected in the speedo. Just my .02

 

[roadtriper]

The engine is working a lot harder to get the truck moving and keep it there with 3.42's and 33's.
The higher gears will have him shifting sooner, and put the engine closer to its sweet spot. Lower gear less work, but too low, and highway mpg will suffer.
Kinda like finding that perfect gear on a 10 speed bike when peddling into the wind, or going up hill.

Point taken! but I believe a well tuned 454 with a TH400 behind it and 3:42 gears shouldnt really notice the difference between 31's and 33's at highway speeds?
just out of curiosity fireman what rpm are you running at doing Highway speed with the 33's ? Maybe I'm all wet here, I've not run 33's on any of my trucks.
RT

 

[juicedimpss]

my crew cab 454 was somewhere in the 7-8mpg.
Its getting a LS transplant. I can't say I am sad to lose the RAT.