I have a 1974 F100 4x4 with 360 ci automatic tranny and full time four wheel drive. I am getting 8 mpg. It is killing me. I want to know what anyone else has done to get the most out of this engine milage wise. I am running 32x11.50x15 tires stock rear end with a remaned Motorcraft 2bl carb. I also have a 1977 F150 that has manual locking hubs. I am planning on swapping out the front ends to give me manual locking hubs and disc brakes up front. What kind of milage can I really expect to gain from this swap. I have the complete truck it has a 351m and automatic in it. Not sure about the motor, owner said the guy he got it from says it was smoking but ran good. Would it benifit me to try and get this motor going for the milage, or is it about the same? I know this is alot to ask in one post, but I wanted to get all the info I could, so as not to spend money needlessly. As always, thanks for all your help.

 

Read post #15.

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Stick with the 360. The 351 M is a boat anchor. Changing the front housing won't work unless you also change the transfer case or install a part time kit in the 203. Stock rearend ratio could vary immensely.Likely 3.50s in a 1/2 ton. This should give you something to think about. No doubt there will be people telling me how wrong I am but thats life.

 

I would love to keep the 360 because it runs so well now. I would be changing the transfer case as well with the front end swap.

 

Make sure the front housings both have the same gear ratio or change front and rear. You may want to change them both if the 77 has a lower (numerically) gear ratio for a little better mileage if you drive a lot on the highway. The 360 should have enough bottom end torque to pull the 3.50 gears with the 32s.

 

I haven't double checked everything, but the axle codes on the door are the same on both trucks.

 

I was in your shoes not six months ago. My truck is exactly the same, but with the original factory tire size. It also has a bad tranny...but that's how it goes.

Anyways, I too got 8 mpg. No more, no less. Do I think that can be improved? Yes! At a cheap price? No!

You truck probably has low gears (just a guess though). Fitting some 235/75R15 tires may or may no help...it's the factory size and slightly lesser strain on the drivetrain. An exhaust upgrade would also be fairly effective (I can't prove it though, never got a chance). The swap to a 351 probaby wouldn't net you a great increase, if any at all. Maybe 10 mpg, just a guess. That 360 engine is a good one (slight oiling issue), with great potential if you've got the wallet to pay for it.

If gas mileage is what you want, my advice is to buy the cheapest, smallest little car you can find and put just enough money into it to keep it running alright. You probably love your truck as much as I love mine, but these trucks need a lot of TLC (and even more money) to be updated to get fair gas mileage and performance.

Just my two cents. Best of luck.

 

you should do a quick search on MPG, there are many posts. If I was you, I would keep the 360. As far as the axle, you don't need to change out the entire axle, just get locking hubs for your axle. But this is important, you MUST NOT drive with your NP-203 full time t-case with the hubs unlocked. you can get a part time kit for your NP-203, or better yet, keep your eyes out for a divorced (assuming your NP-203 is also divorced) NP-205 part time t-case.

 

No divorced t-cases in the half tons - but I agree with bigperm on the conversion. It will be less of a headache to convert the 203 to part-time, even if you still swap front diffs for the disc brakes. You'll also enjoy having the ability to have a low range without turning the front driveshaft - comes in handy often when you just need some extra torque, but don't necessarily need 4wd. Can't be of much help with the gas mileage - my only experience is with the 302.

 

For milage you need to get rid of that auto tranny. My 74 F100 4x4 with a 360 4spd 3.50 gears and 31" tires gets 13-14 mpg driven carefully.

 

The key word would be (CAREFULLY) Not automatic!!!!!!!!!!!!!!!

 

Um OK .

 

I guess the only thing worse is the 400. OK What?

 

Don't even start!!!

 

I think that you started with the boat anchor comment........ so let the misinformed opinion go . Later .