Gas MPG Questions

[1971ChevyTruck]

I have a bone stock 350, 2.02 heads and nothing else. I am running a 600 cfm Edelbrock carb, 700R4 trans---as you can see nothing fancy...what kind of gas milage do you think I will see with this combination--on the highway 65 mph??

[Gorn]

Between 8 and 20 MPH

[cdowns]

depending on what rear you have// if 373 or so i'd say about 16mpg if your engine is tuned up properly

[72swb_327stroker_?]

Originally Posted by Gorn

Between 8 and 20 MPH

sarcasm at its finest!!!!

hahahahahahaha

[griesel72]

yeah, these trucks don't get too bad, my healthy 350 with a 308 rearend 4X4 and a 4 speed gets between 13 and 15, and the last time i checked, that is not much better than the new gm's

[piecesparts]

You need to look at your tire size, rear end ratio, and RPMs for the speed you choose. Once you know these, then you can figure closer what your mileage should be. If your tires are TOO tall, then you will work your truck to death getting up to speed and overcoming hills. If your tires are too small, then the RPMs will be high. Changing tire size is the equivalent of vchanging rear end gears. If you are geared too low, then you will run high RPMs and the mileage will be bad. If you are geared to high, the engine will work harder in a city type of driving, but will be smoother on the highway.

Is your exhaust and air cleaner restrictive on flow? That will change gas mileage a lot. Getting rid of the stock belt driven fan is worth a single MPG gain.

[Gorn]

Originally Posted by piecesparts

You need to look at your tire size, rear end ratio, and RPMs for the speed you choose. Once you know these, then you can figure closer what your mileage should be. If your tires are TOO tall, then you will work your truck to death getting up to speed and overcoming hills. If your tires are too small, then the RPMs will be high. Changing tire size is the equivalent of vchanging rear end gears. If you are geared too low, then you will run high RPMs and the mileage will be bad. If you are geared to high, the engine will work harder in a city type of driving, but will be smoother on the highway.

Is your exhaust and air cleaner restrictive on flow? That will change gas mileage a lot. Getting rid of the stock belt driven fan is worth a single MPG gain.

In addition to that:
The Jets in the Carb and your Cam shaft can greatly effect milage.

[Zonaman]

Originally Posted by 1971ChevyTruck

I have a bone stock 350, 2.02 heads and nothing else. I am running a 600 cfm Edelbrock carb, 700R4 trans---as you can see nothing fancy...what kind of gas milage do you think I will see with this combination--on the highway 65 mph??

I'm set up very much the same as you. I keep pretty close tabs on my mileage. The best I've ever done was Tucson to Phoenix (at about 65 all the way), no a/c. Got 13.8. I usually get 11.6, around 10 with a/c. that's combination city & highway. That's with an Edelbrock 1406 carb. I think the consensus around here is that the Qjet is more efficient. Myself I'm thinking of going to a tbi setup at some point.

[Mint68]

Wow, I have a bone stock 70 Blazer with 82,xxx miles and 31" tires and 3.08 gears. I'm always amazed by the gas milage others are geting. I dont think I ever hit over 10, I seemed to always be in the 7-8 range. Hopefully the tires are throwing the odometer off and it is not counting correctly, because everytime I check it is painfully low.

[1971ChevyTruck]

I have a 3.73 rear end...

[72swb_327stroker_?]

is it a posi?

[MrGoodpliers]

I've seen a few of these threads and I'm always surprised at how small the milage numbers are for the overdrive swaps. I have a 72 1/2 ton suburban with 350, dart s/r heads, mild cam, edelbrock intake and carb, 350th, 3.08 gears. 15 mpg highway.

[1971ChevyTruck]

You an me both...there must be some heavy feet in here