My dad runs a 390 w a 428 crank and a c6 in his F250 super cab 4x and claims 15 miles to the gallon with 35" tires and 4.10:1 gears. I don't know what my 390 gets, speedo is unhooked. I would be willing to bet that with the right combination of parts and a "mileage" tune that 20 could definitely be feasible. I don't think it is out of the question at all.
If you can get 15 mpg out of a 390 in that combination, you should be nominated for the Nobel Prize for Fuel Economy.
If you can get 20 out of a 390 in a truck--overall, not downhill one cool afternoon with a tail wind--you should GET the prize.
What, pray tell, is a "mileage tune"? How does it differ from a standard make-the-engine-run-as-good-as-it-can tune?
If it were possible to "tune up" an engine to go from 15 to 20 mpg overall, then do you think the manufactureres would pick up on it, and new trucks would be getting 30 out of 4.6 motors?
If the T85 is the same tranny that was available in the 289's of the 65-67 era, then I have reservations about its strength. I knew of a 65 fairlane with one and he kept rippin it out (broke). But then he was trying to "Hot-Rod" the thing all the time.
I dont know if the Gear Vendors add on OD is the same as the old Doug Nash/Richmond Gear OD, but if it is, then it isnt worth the trouble. First off, it is only a 20% OD (.80) which is not cost efficient even back then. Secondly, the idea of 6 gears with a C6, while it may sound good and look impressive, I can promise you that you will not be able to shift it that many times even remotely easy. Thats in at the top of the gear, and out while shifting up to another gear, then in at the top of that one----and so on. While it was "electrical" shifting, it was--Lift throttle, hit button, wait, CLUNK! On top of everything else, the DA#* thing whined and howled. I had one in a 76 E250 Club Wagon, 460/C6. It was a Richmond Gear product. Maybe Gear Vendors is different, but I doubt much different. I could have bought hermetically sealed muffler bearings for that money
'65--Mustangs used the Ford top loading "303" all synchro 3 speed. It had several variations and was used behind 390s as well. Mine wore out, but never broke.
Not sure of the history of the GV unit, but I've not seen the Richmond connection. I did see reference to "Laycock" type OD as used in Volvo's and other European stuff.
The Doug Nash/Richmond was a bolt on Overdrive unit. It included an adapter for the tailshaft of the C6 (actually replaced the tailshaft). I became interested in OD's because the 460 van w/3.31 gears felt like it could pull extra gearing (economy!) with a light/no load cruise. Supposedly you would break the C6 before breaking it.
A small control unit bolted to the blinker shaft, and it was electronically shifted. It was only a 20% OD. Actually it was available as an underdrive also. I thought 20% was not enough, 30% would have been better. Strong, but not very easy to use (shifting).
I know about the 3.03's, had one in a 65 comet caliente. They were not OD's. Along that time, there was also available a 3 speed w/OD. Dont think it was 3.03 based. Maybe it was the T85?
My dad runs a 390 w a 428 crank and a c6 in his F250 super cab 4x and claims 15 miles to the gallon with 35" tires and 4.10:1 gears. I don't know what my 390 gets, speedo is unhooked. I would be willing to bet that with the right combination of parts and a "mileage" tune that 20 could definitely be feasible. I don't think it is out of the question at all.
Scott, When you are around these trucks and engines you pick up a few things. When you add the weight of a F250 SC 4X4 brick bat, turning 4.10 rears, mileage is usually in the 6-8 mpg range. Getting it to 9-10 would be some feat. I have gotten 13.5 with my FE running a 390 cfm carb. turning 3.00 gears that is much lighter than your dad's truck. The speedo gear is probably off pretty bad.
I remember some cars with 390s getting 18-19 back in the day. They were much lighter and more areo.
Don't want to be dissing someone but the numbers don't add up.
John
__________________
In the cool still quiet hours of night, you can hear chevies rusting away.
If you can get 15 mpg out of a 390 in that combination, you should be nominated for the Nobel Prize for Fuel Economy.
If you can get 20 out of a 390 in a truck--overall, not downhill one cool afternoon with a tail wind--you should GET the prize.
What, pray tell, is a "mileage tune"? How does it differ from a standard make-the-engine-run-as-good-as-it-can tune?
If it were possible to "tune up" an engine to go from 15 to 20 mpg overall, then do you think the manufactureres would pick up on it, and new trucks would be getting 30 out of 4.6 motors?
LOL...ain't it the truth!
Peeps can spend $1000.00, peeps can spend $10,000.00.
Either way, it makes no difference.
No matter what ppl do, they'll be lucky to see no more than a 2-3 MPG increase in their trucks highway gas mileage.
The city MPG won't change at all.
These trucks have the aerodynamics of a brick, gas was less than a buck a gallon back then and no one gave a damn about gas mileage.
You want better gas mileage without spending a dime?
Keep your highway speeds under 60 miles an hour.
------------------------------------------------
I ain't just whistling DIXIE!
1965 F100 390 with T-85N overdrive, 3.00-1 rear end. City: 8-12 / With O/D: Over 20 MPG on the highway is possible @ 45-50 MPH / At 60 MPH, the MPG drops to under 20 / At 65 MPH, it's drops to 17-18.
The highway MPG was not much different when the truck was a 352 with a 3.25-1 rear axle ratio.
__________________ Bill / Retired Ford Partsman ~ 1962/97
Part number research: Trucks 1948/02 / Cars 1949/91
I have a 390, 4 barrel, 4.10 gears and a 25lbs foot. I'll be happy with 9 MPGs. The 1963T-bird I had in high shcool got 12. I'd like to have that one back!!!
Less than a dollar a gallon, I remember when the first gulf war kicked off. My parents were pissed when gas went over a dollar. I was in 5th grade. I only get 15MPGs with my dodge.
__________________
Bill,
1968 F250 (soon to be brown and orange)
Camper Special, 390 4 Barrel, C6, 4.10 rearend MY TRUCK
2001 Dodge 2500
Quad Cab 5.9 FAMILY TRUCK
my wife drives a Honda, but she bought me the Ford.
I thought the same thing when he told me that, I gave him the benefit of the doubt. He is my dad and all. I asked him if he had converted the mileage for the speedo being off and he said he had. You have to take into account that he was Highway driving in northern Idaho and the speed limit up there is 55 in most areas. That engine is a torquey son-o-gun, beats most Diesels up steep grades. I would be willing to back him on his numbers. He is not one to puff up and lie like a dog.
When doing a "mileage-tune" you set things differently than for a performance tune. Remember that to get mileage you want to burn less gas, to get top performance you burn more gas. I burn a lot of gas. My right foot tends to be toooooo heavy from stop lights. I am told that it comes down to less timing and more vacuum along with a leaner fuel mixture.
I would think that the manufacturers could make a better attempt at making their vehicles more efficient. Little cars from the '70s got the same mileage that new little cars get. I don't see the point of owning a new vehicle. The technology has not improved the design of the automobile over the last 50 years to justify the outrageous prices they charge for their products. The new pickups don't get any better mileage than the old ones, they still have 4 tires, but they are much more complicated to work on.
Sorry, I got off subject.
I don't know much about the overdrives, I would like to have one, but I am not willing to pay the high entry price. I have a buddy that has one in his High Boy and loves it, but I don't remember what kind it is. He claims it makes a huge difference, how much I don't know. The OD is a cool widget though.
The Doug Nash/Richmond was a bolt on Overdrive unit. It included an adapter for the tailshaft of the C6 (actually replaced the tailshaft). I became interested in OD's because the 460 van w/3.31 gears felt like it could pull extra gearing (economy!) with a light/no load cruise. Supposedly you would break the C6 before breaking it.
A small control unit bolted to the blinker shaft, and it was electronically shifted. It was only a 20% OD. Actually it was available as an underdrive also. I thought 20% was not enough, 30% would have been better. Strong, but not very easy to use (shifting).
I know about the 3.03's, had one in a 65 comet caliente. They were not OD's. Along that time, there was also available a 3 speed w/OD. Dont think it was 3.03 based. Maybe it was the T85?
That sounds like the way the GV works. There are pics here, maybe you can spot it as the old one:
The Gear vendors unit looks slightly different. I didnt read the entire article, but they are different.
The Richmond unit had a small adapter (C6) that replaced the tailshaft. The output shaft went into the OD unit and fit into a female splined coupling. I am having to remove some clouds here, but I recall it had 4 fixed shafts on which the sun gears (?) turned. Shifting was done by slider gears and it had no clutches or plates.
The gear vendors unit appears to be much more advanced and may remove the slow "clunking" shifting. Still is the object of cost effectiveness. Maybe some extra merit if is can be moved between vehicles, provided adapters are readily available.
I think NumberDummy straightened me out on the 3.03 and t85 OD's one time on another thread. I asked a question about the 2.02/3.03 and even the daginham 4 speeds. I'm a little slow sometimes, so I better go back and look-see In fact, I even asked about the 3.03 being used in GM vehicles. Maybe the 3.03 was actually a BW tranny.
The 303 was a Ford trans, and it was also sold to GM and used in GM cars. Ralph Nadar hissef made a point out of that once, saying how GM was using Chev motors in Pontiacs and Ford transmissions. I think GM had an ad campaign at the time to "Keep your GM car all GM" or something...except if you need synchros, go to the Ford dealer....
I rarely respond, but wanted to add something I previously read on this forum. BeemerNut stated, “his 69 390 GT with C-6 if driven a constant 62 to 64 mph resulted in 18.9 to 19.1 mpg. This was back in 73 with trips up and down central Calif over a span of 8 years and 90,000 miles.” I don’t know what gear ratio he was running, but I would be very interested to find out. Further, I know trucks are like bricks and cars are more aerodynamic. Just wanted to add this information since we are discussing mpg and 390 FE engines.
The transmisison used in Fairlane 289's was the T86 Borg Warner with the R10
overdrive setup. I have one I found in the back of a 76 Maverick parts car I bought
about 4 years ago! It is the same transmission (basically) as the T90 used in scads of Jeeps for several years. Several internal parts as well as the top shifter cover are
interchangeable. So yes, it is a lighter duty unit than the T85 (which by the way
metamorphed into the BW T10 four speed) and would not have held up behind a
hard driven healthy 289. The T85 is big and heavy and bulletproof.
67 F250 2x4, 33" tires, 3:73 rear, 410 engine built to 400hp+ and the original FMX tranny. Was getting around 9mpg all the time, around town or highway. Changed to a C6 tranny and GV overdrive. Got some pics in my gallery, had to cut down the drive shaft to a one piece. What I like best is its only turning 2K at 65mph. Now get 14 mpg on the highway, still around 9 to 10 in town. I can't imagine ever getting near 20 in a F250, anybody that says they do I tend to not believe, stretching it a little I think. Maybe in a F100 you might get above 15 or 16, but 20, man that’s a stretch.
Ran acrost this tread and fount it realy interesting. I just bought a US Gears 20% overdrive used for 500.00. My 66 F100 had a stock 352 and a mnual 3 speed over drive when I bought it, When I moved to Idaho from Calif a couple of years ago on the trip I averaged 15 miles a gallon running at 1800 to 1900 RPM that was with 27 inch tires and 3.50 rear gears. I have sence added a bit of power to the motor, changed rear gears to 3.07's and swaped to a C6. My mileage on the highway at 65 is around 12 at 2370 RPM with 29 inch tires.The overdrive sould get me back to 1800-1900 rpm at 65. At least some of my milage will return and the motor just seems to like to cruse at that speed. Not sure What I need to do to mount it, looks like the front drive shaft will need to be shortened once more. But im realy looking foward to the lower cruse rpm's. At $4.00 a gallon which it looks like gas will be climbing to, the overdrive will only have cost me 125 gallons and ill make that up in a short while. If you shop you can find deals on used overdrives.
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I thought the same thing when he told me that, I gave him the benefit of the doubt. He is my dad and all. I asked him if he had converted the mileage for the speedo being off and he said he had. You have to take into account that he was Highway driving in northern Idaho and the speed limit up there is 55 in most areas. That engine is a torquey son-o-gun, beats most Diesels up steep grades. I would be willing to back him on his numbers. He is not one to puff up and lie like a dog. 
but I recall it had 4 fixed shafts on which the sun gears (?) turned. Shifting was done by slider gears and it had no clutches or plates.
In fact, I even asked about the 3.03 being used in GM vehicles. Maybe the 3.03 was actually a BW tranny.
