400, 390 or 360
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Senior User
Joined: Dec 2004
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From: Black Hawk,SD
400, 390 or 360
I own a 1979 F-250 4x4 Ranger. As far as I know, everything is stock on it except items that may have been repaired on it before I bought it. It has a 400 in it with a C6 automatic in it. The gas milege sucks. I am sure it needs some tuning up. When I rebuild this truck, would a 390 or 360 be better in it for gas milege or not. Which of these three engines is the best? Are there any modifications that would need to be made if changeing engine sizes?
Michael
Michael
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Joined: Jul 2003
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From: west central florida
the 360, 390 motors wont fit your c-6, the exhaust is different, motor mounts, accessory brackets, etc....completely different motors, your easy choices are to rebuild your 400( if it is a true 400 and not a 351m, the true 400 being the better motor) and use a rv/towing/mileage type cam for really good mileage and torque, or a mild 460 with the same type cam will probably get you better mileage with a properly jetted 4-v carb, headers and a light peddle foot unless you need the awesome power 
Postmaster
Joined: Apr 2000
Posts: 2,838
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From: SD
Mileage will be about the same for all. To change to a 360/390, you will need new motor perches, new tranny, and accessory brackets among other things.
It would be cheaper/easier to keep the 400 and give it a good tune-up and maybe consider a cam and timing set change. These engines were made with the cam timing retarded for emissions, so even a new timing set (at 0 deg advance) will really wake them up. Check the 400 engine forum for more info.
Marty
It would be cheaper/easier to keep the 400 and give it a good tune-up and maybe consider a cam and timing set change. These engines were made with the cam timing retarded for emissions, so even a new timing set (at 0 deg advance) will really wake them up. Check the 400 engine forum for more info.
Marty
Elder User
Joined: Jul 2003
Posts: 504
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From: west central florida
.......then if you are looking to save money on gas, i would save transplant money too and keep the 400, go with the cam, a 4v carb will improve mileage as will headers and free flowing exhaust
Junior User
Joined: Dec 2004
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If you think the 400 gives poor mileage, wait until you try a 360 or 390. I pulled my 360 and installed 460. I get better mileage with the 460. All of the above answers are correct regarding the swap; different mounts, transmission, etc.
Stay with the 400. It's a much better engine.
Stay with the 400. It's a much better engine.
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Laughing Gas
Joined: Jan 2003
Posts: 1,019
Likes: 2
From: Georgetown, Ky
ive got a 390 in my 75 that has a few upgrades, headers, bored, ported, larger valves in the heads.. etc etc im gettin 15 to 16 on the hwy. Provided I can keep my foot out of the back two barrels.
Id keep the 400 or if your really wantin a motor swap.. go for a 460 like has been sugested before.
Id keep the 400 or if your really wantin a motor swap.. go for a 460 like has been sugested before.
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I Have A 360 In A 74 F250 With 3.73 Gears And For 25 Years Have Considered It Fords Gift To The Gas Company. 8-9 Around Town, 10 Highway. In A 79 Bronco W/3.50 Gears I Recently Swapped A 400 For A 428
And The Milage Is Better With The 428 But Not Enough For All The Trouble Unless, Like Me, You Just Want To Do It.
And The Milage Is Better With The 428 But Not Enough For All The Trouble Unless, Like Me, You Just Want To Do It.
Cargo Master
Joined: Aug 2000
Posts: 2,931
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From: SW Michigan
400....or maybe FE ?
Taneum, as much as I am a diehard fan of the FE series, I don't think swapping to a 390 is going to be helpful. 390s are wonderful, but for the money, parts, and time you would spend on the swap could just as easily be spent on improving the 400. The 400 has a problem lots of ford truck V8s have, not enough compression. I think if you were to mill the heads .060 on the decks and intake side of the head ( don't EVER mill the intake itself ), the results would be helpfull. If you jump over to the cleveland forum, Bill B. and his guys should be able to help you. DF, @ his Dad's house P.S. Storm, the 390s are better by a bunch. Nice thing is, you can make a 390 out of your 360 without to much trouble.
