My dad's 88 F250 was getting about 7mpg at the end of its life. Had 250k miles on it though, and he beat the living crap out of it.

BIG engine.

 

I have a 96 F-250 with a 460 in it and the best I've been able to get is 12.5 MPG. Have you received any info on how to possibly get a little more ?
Thanks
Syd

 

Seems to depend mostly on your gearing/tire size and then on how heavy on the rt foot you are. I am running a devorced transfer case so when I am not in 4x my whole front half(drive line included) is NOT turning.

I have had some say no way can you get above 15mpg but I have heard from several that have gotten around 18mpg and one that got 21MPG(ran only 2V carb)

You have all that new smog stuff so I don't know how that may effect MPG.

Also a higher compression can help.

Greg

 

I had my well built 460 in a '79 Bronco with a c-6 3.50 gears and 33" tires and it weighed about 4800#. It would get 10-15mpg depending what my foot felt like.

Now the same engine and trans. is in my '91 F-250HD 4x4 with 4.10 gears and 9.50"x16.5" (about 31" tall) tire and it gets 6-9mpg, it weighs right at 7000#. I did get 10 with it once I drove 160 miles non-stop at 60 mph.

My friends stock 96 F-350 4x4 gets 12mpg with automatic od, 3.55 gears and 235/85R16 tires.

My dads '76 2wd extended cab camper special gets 8-10mpg with a C-6, 4.10 gear and 235/85R16 tires.

 

Brain,

I am running a 74 Crew Cab, 4x4 32.7" tall tires, 4.10 rear gears a NP 4 spd with devorced transfer case, with a 460 and Dv3e heads, the truck weighs #6500. I am running a standard motorcraft 4v carb..

I get around 12 to 14 MPG. I have checked it several times recently, mostly hi way miles.

I have c9ve heads I am going to install and going to change my trans out to a ZF 5spd or AOD among other things to get my mpg up.

Greg

 

Greg,
Your truck sounds similar to mine. Except I have a C-6 and a 750 Holley and C9VE heads. The best I have ever gotten is 10 mpg with a tailwind. Most of the time I get 8. Pulling a trailer I get 6-7 mpg. I wonder if the C-6 is costing me that much mpg?
I have tried driving my truck several different ways, light-footed, heavy footed, and it just doesn't seem to matter that much.

 

I have a 91 f-250, weighs in at 8900lbs, 4.10 gears and 285-75-16 tires and I get 10 MPH. The truck has 190,000 miles and still pulls strong and gets a rock steady 10 mpg, full or empty, in town or on the highway. I know it sounds strange, but I have checked several times thinking it couldn't be right not changing mpg dependant on driving and weight. Oh yeah, E4OD.
T. Roberts
UFD Local 1147

 

My '86 F350 CC dually w/460, 750 Edelbrock, C6, 4.10 gears gets 6.5 mpg no matter what. I tow an 8,000lb trailer and it gets 6.5 mpg. Empty I get 6.5 mpg. It went doen to about 5.5 when I ran it empty at 70 and 80 mph for a few days. Anything around 60 or so it gets 6.5.

 

>But isn't a really big factor here the gearing? My truck
>weighs 6500#s but once I get it moving-- not much hp/tq to
>keep moving but, I have a np 4spd and 4.1 rear end. Would a
>5spd final gear say .76 and a rear end at say, 3.55 really
>move one close to 20MPG?
>

My truck is a '87 crew 4x4 custom cab. No air/no power windows/ no power door lock/ not even a catalytic converter to add weight since it came from Canada.

I have a .40 over 460 (468) with hypereutectic pistons, roller rockers, and a 260 H cam, K&N air filter, headman headers, MSD ignition and ford racing wires. It has the stock (I think original) 650 cfm carb that has seen 125,000(by me)and probably at least 275,000 miles and possibly as high as 350,000 so it is a little worn on idle. I estimate compression to be right at or slightly above 9.0 as the pistons we got were rated at 8.8 and we shaved the heads slightly to insure a flat surface. Driving around empty, I can use 87 octane, but pulling a trailer requires 89 or 91 octane. I also use sythetic gear oil in the transmission and if it weren't for some oil pan leaks, I would be using it in the engine also.

I have the 3.55 gearing and zf-5 speed that you speak of and yes, it helps. 2000 rpms in top gear has me going a comfortable 68 mph. But I don't find the shadow of 20 mpg as of yet. Pulling light loads and/or driving stop and go back roads yields about 10-12 mpg. I was however out to Kansas on I-70 a few months ago and saw at least 14.5 mpg on the way home and may have touched 15 on one segment. This was averaging around 70 mph. When pulling a heavier trailer, (I have pulled up to 20,000 combined weight on one trip) it will still drop down to about 8. The taller gearing isn't real favoring of those kinds of weights as there is a larger step between each gear. Fortunately with the newer engine I can wind 3rd gear up to about 60 mph comfortably.

When pulling trailers, I often wish I had the 4.10 or else a 6 speed or even a dual range transmission.

20 mpg in a truck??? I'd say you'd have to be turning no more than 1500 rpm's and have a 2 barrel carb and gearing to propel you about 60 mph. Pump the tires up to about 90 and do all the other tricks (magnets, and tornado's) and hope for a tailwind.

Years ago, there was a mpg contest for various modes of transportation held in California. This was in the late '70's. Craig Vetter who used to design motorcycle fairings was involved in it, and he spoke at a motorcycle gathering 2 years ago in Ohio. He, as other's here have mentioned, came to discover that the #1 factor in improving fuel effieciency is reducing air drag. So pushing a shoebox through the wind will probably never be able to the most efficient way to go.

Tony

 

So pushing a shoebox through the wind
>will probably never be able to the most efficient way to go.
>
>Tony

I 2nd that!

Hey Tony, off the subject, but I noticed you have hypereutectic pistons. Did you gap the top ring by the manufacturers specs, or some other gap? Just wondering, since the engine seems to be working out pretty good.

 

>So pushing a shoebox through the wind
>>will probably never be able to the most efficient way to go.
>>
>>Tony
>
>I 2nd that!
>
>Hey Tony, off the subject, but I noticed you have
>hypereutectic pistons. Did you gap the top ring by the
>manufacturers specs, or some other gap? Just wondering,
>since the engine seems to be working out pretty good.

I remember reading some tech articles about early hypereutectic piston failure being attributed to rings not gapped properly. In fact, my engine builder almost persuaded me against hyper pistons because he hadn't kept up to date on the new proceedures and had a bad impression of hyper pistons based on early failures and seperation. After he did some new and further reading, he really changed his tune and talked be "back into" hyper pistons. We went with Keith black Silvolites, just because that was a name I was familiar with and because of the in depth tech articles I found on their site.

To answer you question, we went with the manufactures recommended ring gap. The keith black website mentioned early failure of the piston tops coming off, but then went into an explaination that they were improperly gapped, so we figured they knew about the problem and knew about what they were talking about. I also use a 180 thermo to try to keep heat under contro a little. We also kept a pretty keen eye on the quench area.

All in all, I'm pretty pleased with the engine. But in retrospect I would maybe try a basic RV cam and/or go with the 68-71 timing set. (I think that's the one that isn't retarded). It's probably time for a new carb in the near as it has some rich tendencies on cold idle.

Tony

 

Here's a couple tech articles from the Keith Black website. They both talk about piston ring end gap, but the first article deals exclusively with the subject.
http://www.kb-silvolite.com/speclear.htm#CHART
http://www.kb-silvolite.com/page05.htm
Tony

 

>Here's a couple tech articles from the Keith Black website.
>They both talk about piston ring end gap, but the first
>article deals exclusively with the subject.
>http://www.kb-silvolite.com/speclear.htm#CHART
>http://www.kb-silvolite.com/page05.htm
>Tony

Yeah, Those articles are the reason I asked. I assume then you followed those recommendations. Without exception, every machine shop here in town that I called would NOT follow those. I think I called about 8 or so. And they all claim to be experts and they use KB's all the time.

 

I guess I really don't know for sure what specs he used, but I assumed he used these specs. He may have read something different. Do the shops in your area think these are too big or would they go bigger. I've not seemed to have any problems thus far aside from the formentioned need to run 89 octane.

Tony

 

>I guess I really don't know for sure what specs he used, but
>I assumed he used these specs. He may have read something
>different. Do the shops in your area think these are too
>big or would they go bigger. I've not seemed to have any
>problems thus far aside from the formentioned need to run 89
>octane.
>
>Tony

Glad you asked, I'm getting so frustrated with this whole deal. All these guys in town would go smaller!!! The guy that bored my block, said he would go .022 top ring MAX! KB recommends .029 MIN! Everybody else in town recommends .016 - .018 and one guy said he would send rings back if they measured close to .029 out of the box and runs KB's almost exclusively. Most guys here think I should follow KB, but I would really like to know why/how these guy get away with small gaps?

you can read my post here https://www.ford-trucks.com/dcforum/DCForumID11/1628.html

Since then, I make it a habit to ask whoever has them.
Any advice is appreciated.