Fuel Compsumption 396 4L80E

[ahoke]

Anyone have a 396 paired with a 4L80E? Curious what roughly the mpg is realistically. Have a '70 3/4 GMC that I'm swapping a '66 396 block with a mild cam in and looking to pair with a 4L80E. Essentially want to make a bulletproof setup to where I can drive on the highway and tow/haul when I need. Have the stock rear gearing.

[ahoke]

Been sitting since '96. 3/4 ton with a dump bed on it.

[WorldsCrappiestTruck]

Curious your plan for controlling the 4L80E. Standalone controller system? I’d guess mileage overall will be pretty poor. A bulletproof setup would be a 6.0 and 4L80E….but mileage again won’t be great at all…

[Sicklajoie]

Im assuming you've got 3.54 gears?

[weq92f]

.

I suspect, given that you're going to be pushing a brick through thick air with a BBC and a bulletproof, power robbing tranny, the MPG will be somewhere between 10 and 15 when you're keeping your foot out of it. If you're driving it normal or towing, expect the number to be closer to 10.

-Kevin

[kwmech]

Big Block and fuel mileage should not be in the same sentence.

[HeavyHauler]

Originally Posted by WorldsCrappiestTruck

Curious your plan for controlling the 4L80E. Standalone controller system? I’d guess mileage overall will be pretty poor. A bulletproof setup would be a 6.0 and 4L80E….but mileage again won’t be great at all…

Probably not very good torque though for towing with that 6.0.

[HeavyHauler]

Originally Posted by weq92f

.

I suspect, given that you're going to be pushing a brick through thick air with a BBC and a bulletproof, power robbing tranny, the MPG will be somewhere between 10 and 15 when you're keeping your foot out of it. If you're driving it normal or towing, expect the number to be closer to 10.

-Kevin

I remember 15 or 16 with a very mild 454 and a turbo 400.

[72c20customcamper]

Originally Posted by HeavyHauler

I remember 15 or 16 with a very mild 454 and a turbo 400.

Find that hard to believe . I’ve never gotten better than 13 with my 350 with a th 350 . But it has a 4.11 rear

Friend has a stock 454 with a sniper and a 6l80 and he barely breaks 13 .

[Steeveedee]

402/400/3.54, the best I ever got was 13. That was with the shell that was level with the cab. My wife is 5'-6" and can stand up in the new shell. That bricked the mileage, it gets about 10 now.

[truckster]

Originally Posted by kwmech

Big Block and fuel mileage should not be in the same sentence.

"Don't expect any kind of fuel mileage with a big block."

See, you just have to phrase it correctly.

[ahoke]

Appreciate the helpful comments.
Standalone controller for the transmission. Not sure the actual gear ratio. Was getting about 18mpg with a 350/th350 in my '72 C20. Was hoping for the 10 to 15 range if I'm lucky. Trying to keep my setup as wire free as I can. Was looking at a 700r4 but haven't heard the best reviews compared to a 80e. Already have the 396 on the stand.

The whole "don't ask about fuel mileage" comments aren't productive in the slightest. Not naively thinking that a big block is going to be getting 20mpg, just trying to get a realistic idea of what the consumption will be.

[57taskforce]

My factory fuel injected 454/4l80e in my 98 k2500 gets 10-12 mpg unloaded with mixed driving. Pita trailer behind it and it will quickly drop to 6-8 if it’s any real load at all. It’s got 3:73’s and 35” tires, so the cruise rpms are lower than the 235/75/16 or what ever tires that it had from the factory. It could use injectors so I guess maybe it could be a little better but I’ve been driving it since 2004 and it’s always gotten 10-12 mpg on average. The 4l80e takes approximately 50 hp to run with the converter locked from what I’ve read on other boards, so yeah it definitely is a bit of a pig but it is very reliable and durable. If you are going to use it as a truck don’t use the 700R. The 80 is a bajillion times more durable in a hauling, towing, etc environment.

[truckster]

Realistically, 10 to 12 MPG would be in the range I would expect. The best I ever did with any of my big blocks was 16, but that was on a pure mileage run - fill up next to the freeway on ramp, drive 200 miles at 60 MPH, letting it slow going up hills, fill it as soon as I exited the freeway.

If you like to put your foot into it (and who doesn't with a big block) you might expect 8 to 10 MPG.

['68OrangeSunshine]

I had a '67 K/10 Suburban with a 454/TH350/NP205 and 3.73 gears
On a good day I got 6 City and 8 Highway MPG.

They ain't VolksWagens.

[Accelo]

Originally Posted by truckster

Realistically, 10 to 12 MPG would be in the range I would expect. The best I ever did with any of my big blocks was 16, but that was on a pure mileage run - fill up next to the freeway on ramp, drive 200 miles at 60 MPH, letting it slow going up hills, fill it as soon as I exited the freeway.

If you like to put your foot into it (and who doesn't with a big block) you might expect 8 to 10 MPG.

Mine got 13 on the highway with 4:11 gears.

[KQQL IT]

My 99 with a 454 4l80 4.11 on a 32in tire does 13 with my wife driving 9-11 if I drive.

[MARKDTN]

A Factory SS454 was EPA rated at like 10 mpg. You will have less displacement but heavier and worse aerodynamics and not fuel injected. I would look into a factory 454 TBI setup that would also control the transmission but you want less wires. I would think high single digits to low double digits for mileage with the setup you are suggesting.

[Joyridin]

Originally Posted by HeavyHauler

Probably not very good torque though for towing with that 6.0.

Looking at the torque specs and horsepower, a 2014 6.0l in stock form is pretty comparable to the 396 in a truck. If you go with a 402 in the later years, the 6.0l puts out more HP and torque.

If you opt for a 6.2l in stock form, it surpasses the 396 in stock form by quite a bit.

Obviously if you start changing cams, headers, and a variety of other things, it could go either way.

[kwmech]

"The whole "don't ask about fuel mileage" comments aren't productive in the slightest. Not naively thinking that a big block is going to be getting 20mpg, just trying to get a realistic idea of what the consumption will be."


OK here, expect at the best maybe 12-13 on a good day where you have a tailwind all the time or if you are driving downhill all day you can expect maybe 15 if you don't shut the truck off and coast. Big cubes, require lots of fuel. In the end you'll probably average between 8 and 13. Big blocks are fun and hard to keep your foot out of. My flatbed, 454 mildly built (nothing fancy) with a T400, gear vendor and 4.11 gears and a detroit locker can light up the duals from a standing stop.

[57taskforce]

Originally Posted by Joyridin

Looking at the torque specs and horsepower, a 2014 6.0l in stock form is pretty comparable to the 396 in a truck. If you go with a 402 in the later years, the 6.0l puts out more HP and torque.

If you opt for a 6.2l in stock form, it surpasses the 396 in stock form by quite a bit.

Obviously if you start changing cams, headers, and a variety of other things, it could go either way.

The Gen 5 6.6 gas motor is even better. I had one for a few years in a 22 2500HD. It would run circles around my 1998 in every single way imaginable. Including fuel mileage. Mine had a 6l90 behind it and it was a pleasure to drive.

[AussieinNC]

Originally Posted by ahoke

Appreciate the helpful comments.
Standalone controller for the transmission. Not sure the actual gear ratio. Was getting about 18mpg with a 350/th350 in my '72 C20. Was hoping for the 10 to 15 range if I'm lucky. Trying to keep my setup as wire free as I can. Was looking at a 700r4 but haven't heard the best reviews compared to a 80e. Already have the 396 on the stand.

The whole "don't ask about fuel mileage" comments aren't productive in the slightest. Not naively thinking that a big block is going to be getting 20mpg, just trying to get a realistic idea of what the consumption will be.

IMHO....

Depending on your use patterns and driving style, 13 mpg is achievable with the 80e, assuming the vehicle is in an unloaded situation. Absolutely stay away from 700r4, as the torque capabilities of the 700r4 in a reasonable build state are nowhere near a reasonable build 80e. Keep your rear gear around 4.11....

Stick to small port heads, they flow at street use levels over the large port heads.

Have fun...

[Greg58]

My 70 GMC with 402/4 speed and 3.54 rear end gets under 10mpg. I have thought of switching to a 4L80, I am curious to what you end up with.
Greg

[breeh]

I've been running a Bowtie Overdrives level 3 700R4 behind a 427 for 20 years. Zero problems. I get 10-12 mpg.

[HeavyHauler]

Originally Posted by Joyridin

Looking at the torque specs and horsepower, a 2014 6.0l in stock form is pretty comparable to the 396 in a truck. If you go with a 402 in the later years, the 6.0l puts out more HP and torque.

If you opt for a 6.2l in stock form, it surpasses the 396 in stock form by quite a bit.

Obviously if you start changing cams, headers, and a variety of other things, it could go either way.

Yeah but you are higher in the rpm range with any LS stuff.