K10 build for best fuel economy

[chico68]

I am getting ready to start a K10 build and wanted to get some opinions on engine trans gear ratios for fuel economy, we all know gas will again get back to $3.00 + a gallon eventually. Currently I have a fresh 350 w/ 2 barrel carb 700r4 w/ 208 case and 3.08 gear ratio. Been tossing around stock fuel inj. set up idea, also the LS motor conversion w/ 700r4 208 case. Like to hear what you guys think, thanks.

[Chevy3+3]

Originally Posted by chico68

I am getting ready to start a K10 build and wanted to get some opinions on engine trans gear ratios for fuel economy, we all know gas will again get back to $3.00 + a gallon eventually. Currently I have a fresh 350 w/ 2 barrel carb 700r4 w/ 208 case and 3.08 gear ratio. Been tossing around stock fuel inj. set up idea, also the LS motor conversion w/ 700r4 208 case. Like to hear what you guys think, thanks.

I would think you couldn't get a lot better mileage than with the set up you have. You could possibly do better with a newer fuel injected engine & tranny combo but it would take a long time to make up the money you spent on the swap. My dad bought a '75 GMC 1/2t 4x4 brand new. The truck came equipped with a 350/th350/np203 combo with 3.07 gear ratio and he could get 15-16 mpg on a regular basis (highway). He had a 91' chevy 1/2t 2wd ext. cab with a 350/700r4 combo that was capable of 20 mpg. Its hard to believe that 30+ years of technology hasn't created the ability to achieve higher MPG's. It probably has but they don't want to us to know..

[Matt Man]

I have been driving my k10 for the last couple of weeks and have been knocking down 13-14 mpg.

New 350, 4bbl quadrajet.
Turbo 350 trans with lockup converter
3.08 gears open diffs
33 x 12.50 tires
60-65mph.

[Chevy3+3]

One thing I will add is keeping close to or the original tire size on the truck will help a lot. Another is to keep your speeds around 60 mph on highway like mentioned above will help as well.

[Pontiac1976]

well the first thing get a 4bbl carb if you staying with a carb set up. the 2bbl carbs that came on the theses years sucked gas. the 4bbl carb if run only on the front are a lot smaller then the 2bbl if you disengage kick down side of the 4bbl carb you get a 2bbl that save fuel lol you will not have big passing gear this way. There a center line like a T fuel saving to left side, to the right HP power. Try to aim for the center first, see how far left or right.
fuel injection would be the best.
If you got more room in your city get a 5 or 6 speed. if highway most of the time 5 or 6 speed manual
If you can drive most of the time 45-47 mph you will get the best fuel miles. the worst RPM is over 3000 RPM.
The less the weight have to drive the better.

[andrewmp6]

What gas mileage are you getting now?

[chico68]

back in the early to mid 90's with a fresh 350 4 barrel .030 sm465 4 speed and 208 case 3.08 gears it was 10 to 13 mpg. need to do better.

[andrewmp6]

Unless you go diesel your not gonna see a huge better then that.

[cadillac_al]

My dad has a 2012 or so C10 and whenever I use it I am surprised that it only gets 17-19mpg. I don't see a square body approaching that. Our speed limit is 75 on the highway and if you go slower than that you are seriously holding up traffic. I figure 11 mpg from my old K10 isn't that bad (at 65-70 and holding up traffic).)

[Edahall]

I get about 25 mpg with the Suburban in my signature. It's a 3/4 ton so you would do even better with this setup in your 1/2 ton. I drive this vehicle daily and did so when fuel was very expensive so I have more than recovered the cost of the conversion.

[tucsonjwt]

I would stay away from diesel. Diesel fuel now costs 40% more than regular gas where I live - no way to recover diesel additional cost and maintenance/repair.

New model pickups with fuel injected V8 engines get 15 city/19 highway until the latest model trucks with cylinder deactivation and/or turbos on V6 engines. I had a 2000 Silverado work truck with 4.3 V6, automatic trans, and 3.73 rear axle which got 19-20 city, 23-24 highway but that was traveling empty and driving like grandma on her way to church.

I think a low horsepower 350 and your current 700R4 and should get close to 14 mpg city/18 mpg highway when running correctly. If you have a heavy foot you will never get good mpg no matter what you are driving.

[Bigstevex4]

Originally Posted by Edahall

I get about 25 mpg with the Suburban in my signature. It's a 3/4 ton so you would do even better with this setup in your 1/2 ton. I drive this vehicle daily and did so when fuel was very expensive so I have more than recovered the cost of the conversion.

I was going to throw the BS sticker out until I read what you have in it. nice set up!
I get amused with some claims made on mileage. or I have to accept everything I've owned just got way worse mileage than there's!
it can be so easily skewed. the difference on topping your tank off and not can make a couple mpg difference. what direction the wind blowing elevation loss or gain, I can drive the Fifty miles to Rapid city and get 17mpg and on the return trip get 11mpg.

Say you had a 100 mile commute your getting 10 at $2.50 gal= $25.00
LS swap now your getting 15 at 2.50 for a 100 mi=16.66 saved$ 8.34
8.34x 24 days' month $200 a month $2400.00 yr it will pay for itself in 2 yrs
Except I commute 50 mi a yr. well 4 yrs.
Except in reality the gain wont be 50% more like 25% so 8 yrs.
Do the math see if it pays . Or if your just looking for an excuse to swap motors go for it!