8 MPG?

[shiftpro]

Tell me how! I've changed over to EFI and still only get 7mpg if I'm lucky. I have a feeling I've got to tear it down and rebuild it.

And so many think that EFI = more power and better fuel economy... EFI is good for cold starts and... that's about it imo.

 

[Vbb199]

Th400. Not sure about gear ratio

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If you're sporting a carb 350, th400 with a 4x4 truck, and more than likely a 3.73 with the 35" tires, I don't see real big mpg numbers in your future anyways.

But this is small tire sbc guy problems.

Step into the world of big tires and big blocks, and you forget mpg, it's more gpm lmao


A fresh new ignition system surely helps,
But how fresh is the internals of your motor?
Loss of compression can contribute to some of it.

Those vacuum readings arent incredibly great.

If the gauge is bouncing, you could have yourself a vacuum leak.
If so,
GENTLY spray carb cleaner around your motor (mainly intake area) and if you have a vacuum leak.

If it's a steady low vacuum, you could have a loss of compression possibly?

Have you checked leak down on your cylinders before?


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[Vbb199]

And so many think that EFI = more power and better fuel economy... EFI is good for cold starts and... that's about it imo.

Exactly why I bought mine for my 502.....
Who tf wants to fight that when it's cold

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[CoggedBelt75]

I can squeeze 10 mpg on the highway. In town....not so well. Sb with a few bolt-on parts, 33 tall rear tires, 4.56 gears. Ran efi for several years and didn’t get any better mileage.

 

[Chevyguy]

One thing I noticed not mentioned. Have you corrected the speedo for the 36' tires? If not , you are putting more miles on than indicated, hence lower MPG.

With 35's and 4:10 gears/turbo 400 I'm 5 miles faster than what my speedometer reads in my 87 V-20. I average 12 miles per gallon.

Clayton

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[80BrownK10]

That’s about right

I’ve bought several trucks that were stock and lifted them
My experience has been

Figure 13-14 mpg bone stock with no lift and 225 28” tires

And you will lose 1/2 MPG for every inch of additional tire diameter

and 1/2 MPG for every inch of lift

So if you do a 6” lift you’re gonna lose 3 MPG and if you go from 28” tires to 35” tires , you’re gonna lose another 3 MPG

The engine makes a difference too
When we did the LS swap and had it tuned , with a 4” suspension and one inch hockey puck body lift and 35” tires with 3.73 axles
It went from 8.5 with the old worn out TBI 350 to 15 with a tuned LS

We also had a 02 4wd Jeep Liberty bone stock with tiny tires and it gets 14

Well then I do pretty good then. I normally get about 10mpg normally if I drive like a grandpa and go very slow and slowly accelerate I will get 12 and towing my 16ft dovetail loaded with my tractor and implements and ATV I will get 8mpg.

I have an 80 with a 350/350/205 combo. It's lifted about 3" and running 33s. 3.07 gears.

Edit: I'll add that I have a quadrajet on an edelbrock intake. And an Edelbrock chrome air cleaner the kid with a top and bottom plate but the actual air cleaner exposed 360 degrees between them (just didn't want people to think it was through the stock setup)

The little thing busted on the speedometer cable that screws into the transfer case (or was it transmission , I don't remember now) it's some sort of adapter for the speedo cable. I need to order a new one I just screwed cable back in but it's a good bit off without that adapter. I found some company online that makes them. I needed to give them various speed reading both gauge and actual speed they said to make it.

Anyone know of places for this part? I think this company would correct for my larger tires with a new one so that was appealing. I'd have to look to find what website it was I was looking at.

 

[lcfman]

If you have a mechanical fan you could go to a clutch fan or electric fan. This might help.

 

[Raybo135]

And so many think that EFI = more power and better fuel economy... EFI is good for cold starts and... that's about it imo.

It does improve Gas mileage. I got a 50% increase in MPG. I went from 4.12 to 6.85. It is other stuff wrong with the engine that is preventing better fuel economy. But hey, I don't call it 6.85 Miles per gallon, I call it 6.85 SMILES per gallon.

 

[Red Rex]

84 GMC 4wd short bed
350 quadrajet on weiand intake
3.08 gears
Th350 transmission
MSD pro billet dizzy w6a box
30 inch tires

10 mpg @55

 

[78C10BigTen]

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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Where do you have that hooked too?

 

[78C10BigTen]

Down a steep hill! [emoji23]

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With a running start lol

 

[80BrownK10]

Where do you have that hooked too?

He said to the brake booster line

 

[QBuff02]

And here I was happy with roughly 6 mpg in the ol 8-Deuce. Some of you guys are doubling or tripling me! I'll take my Big Block, Big bore 4 barrel carb sucking cool night air just about any night. But there are some guys that have tweaked and tuned and worked out every mpg possible and make these things do quite well. But it's gonna take you some parts and some patience to see any noticeable gain.

 

[Wumbo]

From what I’ve seen, 3/4 ton trucks don’t come with full floats, but rather a sf.

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[dvdswan]

Frankenchevy said: ↑
From what I’ve seen, 3/4 ton trucks don’t come with full floats, but rather a sf.

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IIRC, it depended on what GVWR/brake system was ordered for 3/4 Ts. Could have been either SF or FF