Poor mpg

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clendon1

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I get 6-7 mpg but thats because the way the truck is built : 468 ci, th400, 456 gears , 31x16x15 tires just driving normally.
 
Shorty81

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I get 10 mpg, 496, sm465, 3:73, 31x10.5x16. Driving like old man.
 
80BrownK10

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Les Maples said:
Ok did a compression test and all 8 are in the 164- 167 range so what I'm understanding this is good. I reset my timing to 8 degrees past tdc I'm having good power no idle issues and it's running smooth. I'm keeping my fingers crossed that my mpg increases. We will see in the next few days

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That's all good numbers. Very healthy compression and perfect balance.
 
80BrownK10

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SquareRoot said:
When I was in high school my buddy and I would sneak around the country farms looking for squarebodies after dark. Then we would take our piece of garden hose and siphon out 5-10 gallons of fuel. The money we saved on fuel paid for the beer for the night. Not saying it was right but just saying.
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Why just squares? Haha
 
80BrownK10

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clendon1 said:
I get 6-7 mpg but thats because the way the truck is built : 468 ci, th400, 456 gears , 31x16x15 tires just driving normally.
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Probably normal for a huge big block and stump pulling gears.
 
Les Maples

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Ok day 2 and I stopped to fill up I'm glad to say after 46 miles I only filled up with 3.86 gallons. That's almost 12. MPG. That's a big difference. I want to thank all of you that have me a helping word
 
Les Maples

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Now I won't have to worry about those midnight runs with an Oklahoma credit card (garden hose) looking for gas with anything that runs haha.
 
Maxgforce

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First thing I noticed, long box's have 20 gallon tanks, short box's have 16 gallon tanks, but i have seen people use 16 gallon tanks on a long box, gives room between tank and front spring hanger for exhaust exit. Timing should be 10 BEFORE top dead center, check your mechanical advance and make sure it's working. Autolite 26 plugs gapped at 40. If no vacuum leaks and all other parts are in working order.....then I'd look at your carb closely.
 
Les Maples

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I wish I had a 40 gallon capacity I have saddle tanks at 16 gal each. I am running with AC Delco plugs at .035 Gap
 
RecklessWOT

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Edit- So I finally read through the rest of the thread, glad you straightened out your timing issue! This part still applies though:

You might actually want to try switching to shorter gears like 3.73s or 4.10s. I know having super tall gears is usually synonymous with good mileage, but unless it's all highway you're probably doing the opposite. With how tall the 700r4 is geared naturally you probably have to put your foot in it all the time just to move around, and I'm sure you rarely get out of 2nd gear. If you're going 90 on the highway for long periods of time at like 1800rpm I'm sure gas mileage is awesome, but does it EVER even shift into OD with those 3.08s under normal circumstances?
 
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Les Maples

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Yeah I'm thinking about going to 3.42 or 3.73 but for the most part I drive 2 miles in town and and 11 miles highway at 55 mph so it's up in the air at the moment. And about those Ford plugs.... Nah I'm good. I'm GM all the way. Or nothing.
 
Maxgforce

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rpcraft said:
Yeah I'd never put ford plugs in my GM... Friggin Blasphemy.
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If you go to your local auto store, you'll find out that mid 80's ford and chevy both call for autolite 25's. 26 is just a little hotter spark and detours fouling better.
 
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