hey, i have an 1990 F250 with the 351 in it. unfortunately my engine might need to be replaced. i've heard that the 351 is the worst motor for gas mileage. i was wondering, since i don't have the biggest budget for gas, if there was a engine that would be good to get rather than the 351 i currently have. i'd appreciate any help anyone could give me.
-mike

 

You could get a 460, then you would look back with fondness on the fuel mileage you used to get with the 5.8!! LOL!

 

haha probably but right now it cant get too worst. im already getting only an average of 10 mpg with my current one. atleast with the 460 id have more power.

 

Seriously, on a F250, I would stick with the 5.8 and give it a good tuneup for starters. Unless you drive around empty all the time and act like an egg is under your foot, what you will gain in going to a 5.0, you will trade back out by having to work it harder to move the truck.

 

alright. thanks man i was thinkin that but wasnt sure if there was something that would offer decent power with better mileage. always good to get a second opinion you know.

 

I'd drop a 300 6cyl in there! Good power, lots of low end torque, last forever, good mpg, a REAL truck engine!

 

idk, i haul around a boat often and my dirt bikes and lumber. my friend has the 300 in his f150 i think its pretty good. its def. a possibility

 

you also have to think of how much you use the truck if the swap would equal out at some point in the future. For the 300 swap you would need an engine,computer,motor mounts and towers among other things I am forgetting. that is a lot of gas money. Tune up the 351 you have,unless you are running bigger than stock tires you should be able to get better than 10mpg.

 

im running bigger and wider tires on it but i was getting less than 10 before i put them on

 

<table border="1" cols="5" width="100%"><tbody><tr><td><center>1990</center> </td> <td> <center>4.9 (300 ci)</center> </td> <td> <center>150 hp @ 3400 rpm</center> </td> <td> <center>260 ft/lb @ 2000 rpm </center> </td> <td> <center>MPFI </center> </td> </tr> <tr> <td> <center>1990</center> </td> <td> <center>5.0 (302 ci)</center> </td> <td> <center>185 hp @ 3800 rpm</center> </td> <td> <center>270 ft/lb @ 2400 rpm </center> </td> <td> <center>MPFI </center> </td> </tr> <tr> <td> <center>1990</center> </td> <td> <center>5.8W (351 ci)</center> </td> <td> <center>210 hp @ 3800 rpm</center> </td> <td> <center>315 ft/lb @ 2800 rpm</center> </td> <td> <center>MPFI </center> </td> </tr> <tr> <td> <center>1990</center> </td> <td> <center>7.5 (460 ci)</center> </td> <td> <center>230 hp @ 3600 rpm</center> </td> <td> <center>390 ft/lb @ 2200 rpm</center> </td> <td> <center>MPFI</center></td></tr></tbody></table>

 

The I6 300 is the right engine if you need better mileage and a good puller, just don't expect a racer on the highway.

 

I say keep the 351 and do a MAF swap, that should give you a few mpgs

 

You're going to spend a bunch of money to do any swap. And with all of your options you're not going to gain enough to make it worth it. You have a 3/4 ton pickup with oversized tires. It's not going to get good gas mileage. I do agree that, unless you're on giant rubber and not driving like a 16 year old John Force, then you should get better than 10. Do the 6 liter tune-up, check the drivetrain (especially the gear lubes), look at a dragging accessory, and maybe think about a seafoam treatment. How many miles are on this engine? Maybe it's getting tired and needs a refresh. You could also open up the intake and exhaust. All these are fairly cheap and easy compared to swapping engines. And besides, who swaps to a smaller engine? That's borderline un-American. If you must swap something then swap trucks for a 300 power 1/2 ton. You'd be better off

Oh and about thisREAL? really?
Yeah! What he said

 

the best milage i ever got with a ford truck had a 460 auto in it but it also had a hi way gears in it but still had plenty of towing power

 

its odometer isnt big enough to count over 100k so its either a little over 100k or a little over 200. car fax says its about 100k but who knows. and yeah but i wasnt going to swap out the engine to get better gas mileage. i was doin it because its slowly dying and mechanics wont work on it because the bolts are breaking and im working a couple jobs and dont have alot of time to mess around with breaking bolts. and im not trying to get my truck to get 30 mpg but i was just thinking if i had to buy a new engine if it would be better to change the engine. thank you for all you help guys.