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Best 300 inline mods/mpg improvements. 
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Joined: Thu Oct 27, 2011 3:05 pm
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Post Best 300 inline mods/mpg improvements.
I have a 96 f250 with a straight 6, im looking for better fuel economy and some good updrades to make more low end torque. The motor is completely stock and it gets 17-19mpg at 55mph. Im planning on towing a tandem axle flat deck trailer 1200km. Where i live we have steep grades and long twisty hills. Any mods that you guys can share will be appreciated.


Fri Nov 11, 2011 2:46 pm
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Location: Spokane, WA
Post Re: Best 300 inline mods/mpg improvements.
Best thing to do is stock up on a supply of your favorite drinks and snacks and start reading this Forum and then go here http://www.ford-trucks.com/forums/forum52/ and do the same there. Take notes, make a plan and work the plan.

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'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.


Fri Nov 11, 2011 5:35 pm
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Post Re: Best 300 inline mods/mpg improvements.
Ive been reading the forums alot. Im looking into a new msd ignition,dist cap/rotor, k&n airfilter, and a new exhaust. I know i need to be carefull when selecting an exhasut for the straight 6. Any suggestions on exhausts that dont sound ricey/done, im not looking for a loud exhaust i just want to increase exhaust flow.


Fri Nov 11, 2011 7:05 pm
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Location: Twilight zone, WA
Post Re: Best 300 inline mods/mpg improvements.
check out the many exhaust posts. I went with a 2 1/2 inch system, flowmaster 50 series, and seemed to improve mid-range power. There also a lot of posts about fuel economy here: aerodynamics, low rolling resistance tires, synthetic oil, driving habits, rear axle ratio all play a role.

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1995 F-150, 300-6, 4x4, ex-cab, sb, 3.08 5-speed, 2 1/2 in. exhaust w/flowmaster 50, MSD + ignition upgrades, canopy, 171,000 + miles Gone but not forgotten: 1965 F-100 240 3spd lwb "the green hornet"; 1991 f-150 300 5sp 2wd sb, 1960 F-250 4x4, 223 six, 4sp with wrap-around rear window, two-tone paint.
Tow vehicle: 2012 F-250 4x4 6.7 diesel XLT s/c lwb 20+mpg


Fri Nov 11, 2011 10:07 pm
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Location: North Reading Mass
Post Re: Best 300 inline mods/mpg improvements.
Tom954x4 and Harte3 are on the right track.
The 300 has a distinctive sound and it changes depending on which system you use much more than a V8. A 2.5 inch exhaust is plenty big enough for a stock or mildly modded engine and it will fit in the stock location all the way back. On a couple of my older Fords I had the exhaust come out in front of the rear wheel which I personally liked, but check your local laws.
No real mods on Nelly Belle, I went with low resistance Taylor spirial core wires, a good cap and rotor with brass contacts, Motorcraft plugs gapped at .050 vs .044 stock, and a 2 deg timing advance to 12 deg BTDC. I change oil every 5k with a Motorcraft filter and it burns about a quart during that time. I do all the other filters once a year along with PCV valve. During the summer this works fine but the winter blend fuel tends to give me a bit more spark knock. I did try .055 and 14 deg advance but it was too much noise for the old girl (over 200k miles) and me (over 60) My stock coil tests out fine so I decided to keep it but I have used Accel and MSD blaster coils in the past with no problems but they seem to have a higher fail rate than the Motorcraft. Since this truck is my daily driver and I'm on call a lot I wanted the truck to be as dependable as possible.
Your gas mileage is actually pretty good. I average about 16 to 17 during my 40 mile commute and have gotten up to 20 if I drive 60 mph. At 70 Mph Nelly Belle will drink a gallon every 18 miles. I can't really tell if my mods made any improvement over stock since it was long over due for those components to be replaced. When I hauled my 4500 lb rv I was pleasently surprised at how well it did. It hauled much better than my older 305s and 302s especially climbing hills and holding speed. I did use 93 octane and I actually got about 13 MPG which is 2 mpg better than any of my V8s could get hauling.
The Mazda tranny is not the best for hauling with its silly high reverse ratio but it did well. If I keep the truck, I will put a ZF from a F250 in.
Regards
rikard

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"If women don't find you handsome they should find you handy" Red Green
Now-95 Black F150 XLT SC 300 5 Speed " Nelly Belle"
Past I6s
250 Chrysler Spitfire, 194, 250 Chevy, 223 Ford, 242,258 AMC, 225 Slant 6, 330 REO GC


Sat Nov 12, 2011 11:02 am
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Post Re: Best 300 inline mods/mpg improvements.
The biggest single highway mileage improvement is probably a tonneau cover. Mine gave about 1.5 MPG increase; no real benefit around town though.

The Flowmaster series 70 muffler is much quieter than the 50. 2.5" is the right size.

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1996 F-150 (tow missile)
1993 Mustang 5.0 (hot rod and auto-x monster)
1982 Tiga Formula Ford (SCCA racecar)
2013 Hyundai Elantra Coupe (daily driver)


Sat Nov 12, 2011 11:52 am
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Joined: Thu Oct 27, 2011 3:05 pm
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Post Re: Best 300 inline mods/mpg improvements.
Im thinking of getting the flowmaster 70 2.5''. Does anybody know where i can buy all the required parts to replace my stock exhaust. Any other suggestions are appreciated.


Sat Nov 12, 2011 1:52 pm
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Post Re: Best 300 inline mods/mpg improvements.
rikard, that's the kind of mileage I'm hope to someday get on my old 85 F150. I did recently swap back to a 235/75R-15 from the 31X10.50 A/T's it had. Hoping that will help a little but with 3.55 gears not sure if it will, but haven't had the chance to check it yet. Was averaging around 13-14 unloaded running 60-65 on the highway. Going to redo my plugs today at 50, and maybe try side gaping them and reset the timing. My timing light is broke so I usually set it using a vacuum gauge.


Sat Nov 12, 2011 3:05 pm
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Post Re: Best 300 inline mods/mpg improvements.
few things come to mind

1) Vacuum gage inside the cab, the higher manifold vacuum (usually) the better economy, even if you have to be in a lower gear due to hills.
2) electric fan, lessening any load to the electrical will improve fuel economy, and if on a temp switch, it will turn off when you hit freeway speeds, helping even more. I know ppl will say the clutch fan is good enough, but the electric fan will prove it's worth.

just a refrence, I have a 200ci, in my mustang, and it's getting 16-19 in the city, and MAYBE 20-21 on the freeway.

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75 bronco-BUCK- 2.5 SL- 2 BL- 5.0-C4- d44 w/disk & tru track- bb9”rear w/detroit- family cage- wagon top- 33”tires

Bronco goal = frame off clean up- new wiring- gas/brake lines- steel fender flares- interior w/ 'modern' comfort- when eng dies nice stock ford EFI i6 300ci with AC+PS.


Sat Nov 12, 2011 4:23 pm
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