78 K5 Gas Mileage

[cstew47]

My 4 x 4 K5 with 35" tires and a 383 stroker is only getting about 6mpg. How does that stack up with any similar squares?

 

[RecklessWOT]

That's about exactly what I would expect to get with that setup. Maybe a couple miles more if driving very carefully or doing a lot of flat highway cruising, but something tells me the kind of guy who puts a 383 in a lifted Blazer just might have a slightly heavy foot. I know I would be romping the hell out of that truck if I had it lol. And from what I've gathered from the few Colombians I've known over the years, the roads there are not really geared towards high speed driving, right? Especially with city driving, or on mountainous terrain gas mileage suffers greatly.

Even in stock form these trucks got terrible mileage, once you modify them the number only goes down more

 

[cstew47]

That's about exactly what I would expect to get with that setup. Maybe a couple miles more if driving very carefully or doing a lot of flat highway cruising, but something tells me the kind of guy who puts a 383 in a lifted Blazer just might have a slightly heavy foot. I know I would be romping the hell out of that truck if I had it lol. And from what I've gathered from the few Colombians I've known over the years, the roads there are not really geared towards high speed driving, right? Especially with city driving, or on mountainous terrain gas mileage suffers greatly.

Even in stock form these trucks got terrible mileage, once you modify them the number only goes down more

You called it. I forgot to mention that I have a 4.56 gearing with a 4L60. The bump stick is a 218/224 with a .465 lift @.50. I built it for low end torque. And you really called it about the roads here. There aren't many flat ones.

 

[cstew47]

That's about exactly what I would expect to get with that setup. Maybe a couple miles more if driving very carefully or doing a lot of flat highway cruising, but something tells me the kind of guy who puts a 383 in a lifted Blazer just might have a slightly heavy foot. I know I would be romping the hell out of that truck if I had it lol. And from what I've gathered from the few Colombians I've known over the years, the roads there are not really geared towards high speed driving, right? Especially with city driving, or on mountainous terrain gas mileage suffers greatly.

Even in stock form these trucks got terrible mileage, once you modify them the number only goes down more

I just noticed on your profile that you have a V10 burb? What engine is that? A viper?

 

[Bextreme04]

I just noticed on your profile that you have a V10 burb? What engine is that? A viper?

With a 4L60 I would expect your mileage to be better. You likely are running pretty rich. What do your plugs look like?

In 87 or later, all square body chevys went from C/K to V/R to distinguish the body style from the GMT400 series chevy trucks that retained the C/K label.

 

[Bextreme04]

For a comparison, my 1980 K25 weighed in at 6,000lbs and is a 350/TH400/NP205. I had at least one mostly dead cylinder, 305 heads on a 350 block, a Comp 270H cam, and I was getting 8mpg around town.

At 6mpg, you are likely pig rich.

 

[ali_c20]

6 mpg is what you get with this setup I guess. Maybe 7 when you tune everything to work perfect.
I get 11 -12 mpg on the flat areas 50/50 city highway. When I visit my friends in the mountains it goes down to 8 or 9.
I run a 5.7 crate, a th350, np205 and 3.73 gears with 32s.

 

[Bextreme04]

6 mpg is what you get with this setup I guess. Maybe 7 when you tune everything to work perfect.
I get 11 -12 mpg on the flat areas 50/50 city highway. When I visit my friends in the mountains it goes down to 8 or 9.
I run a 5.7 crate, a th350, np205 and 3.73 gears with 32s.

I just can't imagine that's right. Like I said above, mine ran like crap and its bigger and heavier than a blazer. I'm also on 35's with 4.10's. I've never seen 6mpg on it.

 

[ali_c20]

I just can't imagine that's right. Like I said above, mine ran like crap and its bigger and heavier than a blazer. I'm also on 35's with 4.10's. I've never seen 6mpg on it.

Maybe the right foot is the problem ?

 

[cstew47]

I just can't imagine that's right. Like I said above, mine ran like crap and its bigger and heavier than a blazer. I'm also on 35's with 4.10's. I've never seen 6mpg on it.

Do you mean you have never been as bad as 6 mpg or as good as?

 

[cstew47]

Well, it looks like I am not an outlier. I'm going to lean the carb down a little more. I am at 5,000 feet altitude.

 

[cstew47]

With a 4L60 I would expect your mileage to be better. You likely are running pretty rich. What do your plugs look like?

In 87 or later, all square body chevys went from C/K to V/R to distinguish the body style from the GMT400 series chevy trucks that retained the C/K label.

I guess I didn't read far enough. I see that you have a 350. I learn something every day.

 

[cstew47]

6 mpg is what you get with this setup I guess. Maybe 7 when you tune everything to work perfect.
I get 11 -12 mpg on the flat areas 50/50 city highway. When I visit my friends in the mountains it goes down to 8 or 9.
I run a 5.7 crate, a th350, np205 and 3.73 gears with 32s.

You live in Austria? Gas is pretty pricey there. Filling the tank must be an event. Here in Colombia premium is about $4,00. I have to get a second mortgage every time I fill it.

 

[cstew47]

With a 4L60 I would expect your mileage to be better. You likely are running pretty rich. What do your plugs look like?

In 87 or later, all square body chevys went from C/K to V/R to distinguish the body style from the GMT400 series chevy trucks that retained the C/K label.

The problem here is that I hardly ever get into the O/D range. The roads are windy and mostly 2 lanes

 

[Bextreme04]

Do you mean you have never been as bad as 6 mpg or as good as?

Never seen it that bad