Poor mpg

[Les Maples]

A work in progress. 5.43 mpg with 3.08 350/700R4. Want better for milage, Any suggestions

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[Les Maples]

Hello, I just got this about 3 months ago and put a 350 in has a 700R4 with 3.08 gears. It was a total mess and now it's a daily driver. Love this truck.

 

[gotyourgoat]

Welcome!

Can you elaborate on things like your driving style, terrain, or engine mods. Hauling anything around?

 

[78C10BigTen]

Thats rediculous! A 350 with 700R shouldnt be that bad! My 350 with th350 and 3.08 was making probly 10 mpg, swapped to 3.42 and still didnt see much change. If i had a 700R i bet id have even better mileage. Id be looking at other components...

 

[Les Maples]

I agree it's totally horrible. My driving habits are on flat land, no load. Stock 350, no aftermarket modifications I'm trying to stay as stock as possible . I drove it today a total of 23 miles an went threw a quarter tank. I'm bummed out about this.

 

[78C10BigTen]

I agree it's totally horrible. My driving habits are on flat land, no load. Stock 350, no aftermarket modifications I'm trying to stay as possible as I can. I drove it today a total of 23 miles an went threw a quarter tank. I'm bummed out about this.

That seems astronomicly wrong! Youve got some sort of issue im guessing

 

[Rusty Nail]

Yeah!

Like;
rear brake drag
differential fluid level
ignition timing
fuel filter
air filter
tune up parts
tire pressure
transmission fluid level
oil level / cleanliness
dirty motor oil will/can suck the life from your MPG.
concrete bumpers

at least you can look forward to doubling your mileage!

 

[Les Maples]

Since I've started building it the list is this. New plugs, wires, distributor, and cap, fuel pump, and filter, new air breather, oil and filter. Timing is 10 degrees before tds. Plugs are gaped at 35. I'm thinking my carb is junk but it fires right up. Doesn't flood out. I'm discombobulated.

 

[gotyourgoat]

What carb? Stock quadrajet?
What was the 350 from originally?

If you let off the gas and the steering wheel how does it coast? Notice any brake drag or pulling to either side?

 

[Rusty Nail]

before / after , what difference does it make anyways!??

serious though.
If your ignition REALLY IS set at 10° before top dead center , that's your problem.

Reset timing to 10° AFTER top dead center, take two aspirin and call me in the morning..

Don't bother posting the fix without pix.

Hope this helps!

 

[1985c20]

Just to be sure you’re calculating mpg by filling the tank driving x amount of miles then refilling the tank and issuing actual gallon consumed right? Some people just go by the gauge dropping a 1/4 tank without actually checking it out and it could be a bad gauge or something. Not trying to insult intelligence levels or anything just making sure

 

[Les Maples]

I have a stock q-jet when I coast the truck runs straight without hands. It does show a little more than my 2000 GMC K2500. But I was thinking that was due to the tires Cooper Discover SST which are at 35 psi. I had the local Chevy shop put new front hubs, bearings, calipers and hubs and new Mile Marker locks.

 

[Octane]

Hello, I just got this about 3 months ago and put a 350 in has a 700R4 with 3.08 gears. It was a total mess and now it's a daily driver. Love this truck.

Maybe your gauge is incorrect.How was mileage calculated?

 

[Les Maples]

Yeah I filled the tank drove to work and back. Then went to the gas station. A filled the tank and it took almost 5 gallons. I drove 23 miles I have 2 16 gallon tanks .

 

[Les Maples]

I think I'm going to put a new q-jet and go back to the stock rally wheels and 235/75/15 tires and see what happens. The 350 was originally in a delivery van. I only used the valve covers everything thing else came from the truck or I put new parts like the flex plate. The truck had a 383 in it before I put the 350 in. I would have loved to kept that in but unfortunately #5 piston came apart. And both heads were cracked. The pic is of the 350 going in

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