8 MPG?

[MisterB]

I know we don't drive these trucks because they get good mileage. Just trying to make sure I have mine dialed in and I'm getting all I can.

1980 GMC K2500 3/4 ton, 35" mud tires, 6" lift, crate 350 motor recently refreshed with new plugs/wires/cap/rotor/K&N/all new synthetic fluids everywhere. Carb has been cleaned, and gas additives run through system. Cooling system flushed, new fluid, hoses, thermostat, and gasket. All new vacuum hoses.

This last tank of gas I didn't do any highway miles (rarely ever do anyway). It was all city, and I got 8 MPG.

Is that about what I should expect with how I have this rig set up?

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[Vbb199]

I know we don't drive these trucks because they get good mileage. Just trying to make sure I have mine dialed in and I'm getting all I can.

1980 GMC K2500 3/4 ton, 35" mud tires, 6" lift, crate 350 motor recently refreshed with new plugs/wires/cap/rotor/K&N/all new synthetic fluids everywhere. Carb has been cleaned, and gas additives run through system. Cooling system flushed, new fluid, hoses, thermostat, and gasket. All new vacuum hoses.

This last tank of gas I didn't do any highway miles (rarely ever do anyway). It was all city, and I got 8 MPG.

Is that about what I should expect with how I have this rig set up?

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Gear ratio?

And it's a th400 trans right?


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[Green79Scottsdale]

IMO, yes, that's what you should expect. I have a '79 K20 with stock 400/400/3.73/31" tire combo and get a consistent 10mpg. These are already aero challenged, and a lift and bigger tires doesn't help.

Love the velcro puppy!

 

[MikeB]

Dual exhaust thru low restriction mufflers? Heat riser valve working properly? If using a cat converter, is it fairly new?

Are mechanical and vacuum advance working properly? A total of approx 45 degrees at low-load cruising speeds will help economy. That's initial + mechanical + vacuum.

 

[Dmack]

Sounds about right. Mine is similar - factory crate 350, 4 speed, 4.11 gears, 4" lift, 35's. I get 10 with mostly in town driving.

 

[Frankenchevy]

Efi and computer controlled timing got me up to 14ish with mostly 50mph rural roads and almost no stops. I only have 33s though. 4l80 should get me a couple more.

8 seems a bit low, but in the ballpark. Maybe get a WBO2 sensor and dial in your carb that way. You could probably get 10-11 with a conservative driving style and a perfectly tuned carb.

 

[MisterB]

Gear ratio?

And it's a th400 trans right?


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Th400. Not sure about gear ratio

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[MisterB]

Dual exhaust thru low restriction mufflers? Heat riser valve working properly? If using a cat converter, is it fairly new?

Are mechanical and vacuum advance working properly? A total of approx 45 degrees at low-load cruising speeds will help economy. That's initial + mechanical + vacuum.

Headers through single Flowmaster.

Not sure about your other questions

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[shiftpro]

Th400. Not sure about gear ratio

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Do you have a tach? What's your rpm @ 60mph?

 

[shiftpro]

A warmed up 350 with 4 barrel in a 2wd can get 20 mpg... I've done it.

 

[shiftpro]

Never get this with a low compression engine.

 

[dvdswan]

Vacuum gage can help with better mpgs.

 

[Arkansas_V8]

I get about 11mpg. V20 Suburban, 37's, 4.10 gears, TH400. That's a TBI, but with no 02, so runs a tad rich.

 

[MisterB]

Do you have a tach? What's your rpm @ 60mph?

I don't have a tach

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[MisterB]

Vacuum gage can help with better mpgs.

Are you talking about a gauge like this? This is the best I could get it adjusted a few weeks ago when I did it

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