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Alright i just rebuilt my engine 351m stayed with same intake and carb two barrel. I put full headers and 2.5 pipe with two 40 series flowmasters. I still get 10mpg. Is it the tire size i have 33x12.5 15s. What is the deal I thougt my engine was tired after 190000 miles so i rebuilt it and thought it would atleast get 12mpg. Whats going on?
 

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The Anti Yam!
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bigsal51 said:
stayed with same intake and carb two barrel. What is the deal I thougt my engine was tired after 190000 miles so i rebuilt it and thought it would atleast get 12mpg. Whats going on?
You have a carb :shrug

What kind of driving do you do?
What gears?
 

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Roller rockers are gay
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what gears do you have? if they're too high they are going to make the engine work harder than it has too and that'll murder your fuel mileage.

GACK: wouldn't a 2bbl get better mpg than, lets say, a 4bbl that is designed for his engine? as it flows less air, and there-fore, less fuel? i'm not carb smart.
 

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1. Your truck weighs about 3 tons.
2. You have a 351 cubic inch engine in said 3 ton truck.
3. You have 33 inch tires.
 

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depends. the 4 barrel has smaller injectors. so if you dotn stomp on the gas with a 4barrel it will use less gas. on the other hand if you have a heavy foot liek uhmm me :duh ill use more than a 2 barrel but i wont have a lazy @ss truck off the line. you running 33" tires prob on stock 3.55 gears. thats prob hitting you harder. i know my truck was stock with 29" (235) so im getting smacked at the pump. upgrade to 4.11 gears which im plannign to do and you shoudl get better mileage.
 

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A 4bbl would get better milage if you keep your foot out of it. You can run smaller primaries and set the secondaries up to come in late.
 

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hey, mines a 93 with 3.55 and the 351w 31X10.50 k&n i always keep rpm around 1700 never higher than 2000 in an effort to conserve and i WISH i could get 10, i get about 9 if im lucky

idk what is wrong
 

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bigsal51 said:
Yea i am running 3.55s. with a two barrel carb. And I run long highway miles.
your a gear candidate. 4.11's for you. unless you want power 4.56. ladeda. im after mileage to. so 4.11. im changing my 9" 3rd member first which i plan to get from ebay since i want a detroit in the also since i have a open diff.
 

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How many miles are on this new engine.....????? It could be that it just aint broken in yet?????
 

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ok you are driving a big heavy truck. with the airodynamics of a brick. if you want better mileage drive 55.

just try it. at 55 i get 18mpg (EFI 30 inch tires) at 75mph i get 15 to 14 mpg. drive slower.

the gears might help but if all you are doing is highway then they probly wont make too much of a difference i wouldn't think.

i know you love the way your truck sounds. now you need to drive it so its as quiet as posible. less right foot. coast more. turn off the A/C.

just my .02$
 

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Zombie Hunter
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If you're running long highway miles i would move up to 4.11's.

Your having to put more skinny pedal into it in order to get those 35's rollin. The 4.11's will help you back off the skinny pedal, but your going to notice a higher RPM in your overdrive gear.

I think 4.56's might be too much if your doing a lot of highway. But gearing is definitely your issue.
 

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Practicing Infidel
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bigsal51 said:
Alright i just rebuilt my engine 351m stayed with same intake and carb two barrel. I put full headers and 2.5 pipe with two 40 series flowmasters. I still get 10mpg. Is it the tire size i have 33x12.5 15s. What is the deal I thougt my engine was tired after 190000 miles so i rebuilt it and thought it would atleast get 12mpg. Whats going on?
The 351Ms were never known as mileagemasters

but there are some, cheap, easy tricks to try before lashing out the big dollars for gears.

First off does your new motor have pep off the line and get up and go acceleration wise ? Also, did the engine come with the advanced (pre-emission's ) timing chain set ? Engines prior to emissions era 351Ms were 4 more degrees advanced by virtue of an advanced cam gear in the timing chain set.

It's a simple as pie to swap an earlier timing chain set on and really wake that puppy up both mileage and performance-wise.

Also, if you're willing to spend under $30 you can buy a Crane adjustable vacuum advance for your distributor and use the following procedure to super tune the thing.

I've done this procedure to almost all brands of V-8s and the gains are outstanding;



Sixlitre
 

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I have an EFI 351W, 3:55 gears, and 33 inch tires. on highway i get about 15-16 mpg, in town i get about 12-13 mpg. the only thing that i would suggest would be to get some 4:11 gears. thats in my bronco's future. although even with my 3:55 gears i have good acceleration, and pep.
 

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dirtydave said:
I have an EFI 351W, 3:55 gears, and 33 inch tires. on highway i get about 15-16 mpg, in town i get about 12-13 mpg. the only thing that i would suggest would be to get some 4:11 gears. thats in my bronco's future. although even with my 3:55 gears i have good acceleration, and pep.

exactly what he said, my efi 91 gets 12-15ish, driving it hard or not. a stock bronco weighs closer to two tons (mine ways 4500 bone stock except for 32's). 10 mpg's average,though with a carb may be as good as you get. Consider the gear swap as mentioned, swap to a 4 bbl carb, and be SURE to keep your foot out of the secondaries.

imo never rebuild a motor just because you "think" it was tired. If it's not smoking, or has tremendous power loss, leave it alone. You'd be damned surprised how long a ford smallblock will run.
 

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i have 94 with 35 inch tire and i get off the line good but i want to put in like 4.11 gears i have stock right now how much would that put me back
 

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last qoute i got was for 4.56 gears frt/rr and install kits...plus carrier for frt ttb at $565 shipped...just waiting for taxes to come in.
 
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