77 c10 305 mpg?

[Kapdin]

Hey guys, Im lookin for a side project and maybe a daily driver. Ive found a 77 c10 witha 305, is it any good for mpg or would swaping it for the 91 350 auto tranny i have still be better?

 

[bucket]

My 2.56 geared '84 gets anywhere from 15 to 20 mpg, it's stock with headers, duals and a Holley. Generally though it's about 16 mpg. If I take a longer trip and the speeds are kept to 55, that's when it picks up the mpg.

 

[Jims86]

23 possible with the 91 TBI motor, 700 r 4 and a tune with highway cruise mode activated.

 

[Kapdin]

23? no joke? **** i should swap that with my other truck lol. id asume it has a 700r4 its 91 silverado 1500

 

[bucket]

23 possible with the 91 TBI motor, 700 r 4 and a tune with highway cruise mode activated.

Do you know the rear end ratio and the speeds that was achieved?

 

[Jims86]

Do you know the rear end ratio and the speeds that was achieved?

Was a C10 shortbox, 3:42...I forget the tire size, but it ended up being around 26 or 27" in diameter on ralleys, and it was typical 70mph out here in Cali. Hwy 5. Measured on a 200 mile trip.
Fuel tank was a modified blue plastic drum, so fuel levels could be visually confirmed.

 

[HotRodPC]

You mean I-5 right??? Not to be a smartass of course. But in OK, mpg is different on a State Hwy that has curves and slow down thru every 1 horse town along the route and some even a stop sign at the one and only stop in the town. So on the Interstate, you do get much better mpg than a State Hwy.

 

[HotRodPC]

Fuel tank was a modified blue plastic drum, so fuel levels could be visually confirmed.

So that's what the hell I"ve been doing wong dammit !!! I use a metal tank under the damn truck. I have some black plastic drums. Will those work the same as the blue???







OK, now I'm being a smartass !!!

 

[Jims86]

So that's what the hell I"ve been doing wong dammit !!! I use a metal tank under the damn truck. I have some black plastic drums. Will those work the same as the blue???







OK, now I'm being a smartass !!!

LMAO!
Yep, I 5, then from the fuel stop in Redding, Up through the mountains in Shasta...only lost around 2 mpg through there...its pretty windey, and a hell of a climb.

 

[Kapdin]

huh, so 350tbi, 700r4, 3.42, 27", 2wd, and tuned? as in flash the computer? or dyno tune? also fyi my c10 i was refuring to sold. was a good deal i guess.

 

[89Suburban]

 

[bucket]

Was a C10 shortbox, 3:42...I forget the tire size, but it ended up being around 26 or 27" in diameter on ralleys, and it was typical 70mph out here in Cali. Hwy 5. Measured on a 200 mile trip.
Fuel tank was a modified blue plastic drum, so fuel levels could be visually confirmed.

Cool beans! One more question though, was that a while ago or more recently with today's crappy fuel?

 

[Jims86]

huh, so 350tbi, 700r4, 3.42, 27", 2wd, and tuned? as in flash the computer? or dyno tune? also fyi my c10 i was refuring to sold. was a good deal i guess.

Just a chip tune....tuning was done in real time, logs were taken while driving, where on a dyno, you dont get wind resistance, differing grades, Etc.
There is a tune done on a k10 burb that yeilds around 19 MPG....that tune was done up in Idaho. I am running a slightly modified version of it in my Burb, we had to adjust the fuel tales for my Comp Cam.
I have seen low 20's with qjets too.

 

[Mark L]

Wow I must have some real issues with my 6 banger. I'm getting around 12mpg

 

[Jims86]

Wow I must have some real issues with my 6 banger. I'm getting around 12mpg

You non EFI guys should take your carb jets down a step...factory carbs are really fat.