You just missed out! There was one on Ebay for 10 bucks! I'm pretty sure it was EFI too. I think the auction ended on June 1st. I'd just search auto trader and find some old junk truck for a few hundred bucks that has a 300 in it, then just rebuild the 300.

 

I have a donor truck for thudpucker...its a 1991 f-150 CUSTOM w/ I-6 /E4OD...only 80,000 orig miles....excellent runner...has like new tires the interior is good as is the cab...the bed has some rust...has good tailgate .....inexpensive....contact chapman14219@yahoo.com

 

Did we ever get together over this donor truck?

 

Hey Guys, first post on I-6 forum. Have read all six pages and no on has mentioned GPS, unless I missed it. Have low end Garmin unit and used it on an 11 week 12,000 mile trip around North America starting last July 12. Truck is 1966 F-250. 4.10 rear, had 650-16 OE and I put on 750-R16 at redo of truck. OE was NP435 trans. GPS has speedometer and odometer. Point to be made here is GPS can give you accurate info. First road test of truck after redo was speedo accuracy. At 50mph GPS, truck speedo was about 43 MPH. Went to parts CD found correct driven gear for my rear ratio and new larger tire size. Ordered and installed new gear, and speedo and GPS read the same at 50 MPH. Two weeks before trip I installed a 1,2,3,OD trans from 1986 F-150 ( Trans really sucks as the distance between 2nd and 3rd gear is as wide as the Grand Canyon as someone said). My speedo cable and gear went right into the 86 trans. OK now another test for accuracy and the GPS found that the Speedometer in the truck was reading 60 mph while GPS read 50 MPH. No time to search for a correct drive/ driven gear combo as trip was starting in couple of days. We used the GPS to log the whole trip resetting the trip log at every fill up and tracking mileage/mpg. Again the point made is, use a GPS for checking for discrepancies between your in dash speedometer and how fast the truck is actually traveling. Some of you may have a GPS or have a friend with one. Hey man how about grabbing you GPS and lets go check out my trucks speedo. The very best MPG I did on trip was 16.5 and I was VERY, VERY DISAPPOINTED. I did have issues with the engine which is a totally majored 240 I-6 and that is another story.

 

IICAP, a 240 L6 seems kind of a small engine for your 66 F250.

However, your 11 week, 12,000 mile trip at 16.5 mpg wasn't too bad.

I '83, I took an Alaska 4 week, 10,000 mile venture, and averaged 19+ mpg,
but that was in an '81 F150 300 L6 T-18 trans, and a 2:75 rear end.

I also drove the speed limit. That may have helped me with my gas mileage.

 

I just came back from a 4hr. road trip in my '76 300 and averaged 21mpg. I was doing an average of about 65mph (it wont go much faster!!!!)

 

Two reminders. Don't do your fuel mileage test on low miles like 50 miles. Run most of the tank to attain alot of miles. There's too much variability on when the fuel nozzle shuts off or when you think it is full. Also, get the accurate reading on miles driven. If you have changed tire sizes or whatever your speedo AND ODOMETER is off. The little "mile number" signs on the side of the freeways will give you an accurate reading. Of course you'll have to fill up both times fairly near one of those signs.

 

And that's why I was mildly pleased with my 19. something mpg when I went on my 10k mile excursion to Ak.

Now that I changed the rear end ratio from 2:75 to 3:50 and went from
P215/75R15 to 30-9.5-15 tires, my gas mileage has dropped to about 16 mpg.

Oh well!

 

Running 31 inch mud tires and a 3 inch body lift on a 1994 f150 4x4 extended cab short bed with the 5 speed and the 3.55 rear end i get about 16.23-17.2mpg mainly country roads i usually drive about 360 miles before fuel up.

 

I hope I dont get too old before a Doner 300 six/auto shows up for my 77 F-150

 

Hey Thudpucker... just noticed that we don't live too far apart. You must be patient as I see your last post for this thread was 11/26/2008.

 

Yup! Anybody with a want and no Money is patient.

I bet we'll meet some time this summer.

 

"There's too much variability on when the fuel nozzle shuts off or when you think it is full"
- 'Full' is when it won't take no more gas and it's layin' in the filler opening. Only real way to be sure - and the truck needs to be sitting level both fill-ups as well to be certain.
Mine is STILL sucking it down, no idea on actual MPG's - but it's not good. 300 with .030 over and a newer head/balance job than the 90,000 on the rebuild. Stock 3-speed manual, 2.75 rear gears (from the tag - yup - still attached) and 235-75-15's. (stock was 195-75-15's and that damn calculator someone posted earlier is hogwash - I KNOW I'm doing 55 when the speedo shows between 47 and 48..) Rebuilt the carb, (several times) and keep the tires to 35 psi. Has a cab-height cap. New air filter in stock frisbee, no cat, no resonator, no air pump, Only power steering, no AC or the like, free heat riser, hand choke just installed and re-hooked up the hot air tube for cold startups. (and it works, too.. watched it open.. )
Just re-tuned yesterday with my vacuum gauge and it must now have like an extra 6-8+ degrees beyond stock timing, heard no knocks driving yesterday and I tried to make her lug a bit after stops - am hoping the choke and timing will be of some help.

- 'Cause it SUCKS fuel in a way my old E150 with a similar setup (no idea of rear ratio, and had the 4-speed OD manual) never did. That got me a regular 17/19 hwy @ 60 MPH or so. The closest specs I can find is for 1984, and that says I should be getting 19 MPG's hwy with the stock tires. These have me rolling 55 MPH actual @ around 1650/1675 RPM's...
Want to add a 4-speed OD manual - but everyone around here thinks the things are made of silver or something. Not sure if the drop in RPM's it would give would make her lug, or add a couple MPG's. Anyone else? How about a different air cleaner setup? Drill me some holes in the outer top or something? grrr...

 

DH your lost in a phase shift of meaningless numbers.
Why'd you have to go .030 over? Was the taper that much? Must have been a "cold Weather" engine. In Fairbanks AK, they idle so much in the cold that a .030 Taper is normal for a two year old truck.

The 3 to 4 speed difference is in the 3rd gear. Not the 4th Gear. You could assume 4th gear is 1:1 and the OD is .86:1 or not much of an improvement unless your on a long trip.
Actually an Auto would give you better mileage for City driving or long Road trips.

The "wrong' Rear end is fixable as well as the Speedometer drive gears.

Down here they are hauling all the old trucks to the Metal Scrap yards. I see some going by everyday. It hurts to know that my old Red Ford will be going down there some day if I don't get going on it soon.

 

I have an '84 Ford F-150 4X4, with a 300 I6 that has 427,000 miles without anything rebuilt, other than the carburetor; I am actually running an old-school carburetor. I also tossed the TFI system for a Dura Spark II distributor, that is now triggered by a GM HEI module. I am also running FI manifolds with dual exhaust. It has 3.08 gearing and my tires are Kumho 31X10.5 ATs. My transmission is a NP435 with the granny low. And, I have the speedo gear changed to reflect the correct speed and mileage.

On a good day, I can get 24mpg on the highway, with a flatbed. I am in Nevada at 7100' above sea level, so I can imagine a slight increase in MPGs at lower elevations. This is a huge, high valley here, so I can put 150 miles on without much increase in elevation.

In the near future, I am going to tear it down and do a rebuild. I plan on boring it 30 over and I also have a solid cam profile I am going to have custom ground -- I came up with it using desktop dyno. It is actually a pretty low duration, with a good split between the intake and exhaust: 188 intake and 202 exhaust, both measured at 50-thousandths. I also plan on getting a full-length header for it, too. See, the more you can improve the bottom-end TQ of an engine, the better the fuel economy that you will get. If you can gear it -- including tires in the equation -- to keep the engine RPMs within this lowered TQ band, then you have won part of the MPG battle. This is why diesels tend to get much better economy than their gas counterparts.

I am expecting an increase in MPGs with the 300 I designed, but it was done more for an increase in pulling power, for pulling a trailer and off-roading.