I've got a 75 F-250 with the monster gas hog 460 engine & a C-6 transmission. Although I am aware that my options are somewhat limited to the 351/400 long block engines when it comes to finding a replacement for my 460. I was wondering if anyone can provide me with a list some of the individual engines, the best years to choose and maybe even some of the best vehicles to find as engine transplant doners.

Of the 351C, 351M or the 351W. Which engine would be considered to be the best replacement canidate?

If a 351 Cleveland engine is a compatible replacement engine? What are the best year & model vehicles to find as doners?

Are any other engine sizes I can consider using?

Any other useful information and/or advice anyone would like to provide. Would also be gratefully accepted and certainly will be sincerely appreciated!

Thanks,

75 SuperCab

 

i would stay away from the 351c in a truck. Its power is made in the high rpm's and is prone to hot spots. If i had to guess id say the gas milage would be about the same as the 460 anyway.

The 351m is the same engine as the 400 except the stroke and they both get about the same gas milage as the other. So if you went this route id go with the 400.

The 351w will probably be the hardest swap and if you wanted relitavly good milage you would probably want to go EFI and that would be alot of work and money.

If i had to do a swap i'd go with the 300-6 because alot of people are claiming 16-19 mpg and more than enough power. If you did this swap you probably could do an AOD from a late model truck also id have to believe.

 

I have a 300-6 and love it because of the torque and good gas mileage. I have one without emissions and to find one without emission you'd have to look at trucks/school busses earlier than 1978, the sticker on the valve pan will say "No Catylis".

I'm not sure if it's legal to put in a non-cat engine in a vehicle as a swap but it's worth looking into.

Oh, dad had a truck with a 400 he got about 11mpg, but man that thing had power. Just a thought good luck.

 

With the size of your truck, I don't think they'll be any big improvement going with a smaller engine. What gears/tires you currently running?

 

I prefer the 460s, though I throw the stock carb in the trash and install a Holley 600 or 650 vacuum secondary replacement.
Heavy trucks get lousy mileage, so the real solution is to drive something else except when the truck is required.

The 300-6 is an excellent engine. If I were ditching the 460 that's what I'd install.

 

I went from a 352/3speed mnual to a 460/C-6 combination, and I get 15 MPG at 70 MPH.
Before you spend the really big bucks on a swap, I would give some real consideration to tuning the engine right - and I do not mean spark plugs.

Read more about this in the 385 forum, but the '72 and later 460s were de-tuned for smog reasons. Up until fuel injected 460s made their appearance, the cam was retarded 4 degrees, robbing the engine of the power and mileage it deserves to give.

I would recommend you put in a so-called RV cam, with an Edelbrock Performer (not the RPM) intake, new 650 CFM carb (750 if you tow or haul heavy loads), and top it off with a straight-up timing gear set from a '70 or earlier 460.

The one thing you will find it expensive to do is to change the rear end gears - I have an F-100, with a Ford 9" rear, and easily swapped out the rear end to a 2.75.

You can get the cam and lifters for about $75, the gears for about $50, the intake for about $250, the carb for about $300 and the gaskets for about $100 (there is a special valley pan gasket for the 460 - sorta kinda like the old Pontiac engines had in the '60s.)

That would cost a whole lot less than a new setup.

If you decide to swap out a complete drivetrain, consider buying a whole junk truck with the drivetrain you want. Any F-100 - 250 from '73 - '79 will have all bolt-up parts. Trucks '69 - '72 will have a bolt up drivetrain as well. It will be so much easier, because there will be so many things that will be different between the 460 and any other drivetrain. This includes the motor perches (that bolt to the frame), accelerator linkage, all sorts of nitnoid frustrations that will drive you mad.

I hope this helps.

 

I had an 84 F250 460 auto 4WD and frankly it got about the same milage as my current 97 F250 351 5sp 4WD. If you are determined to downsize for greater milage go to the 300 six, I don't think any of the V8s will offer a great improvement.

 

I third(or fourth) the 300 L6. you will see an increase in mileage(more than any V8, but still prolly won't be great). Biggest downfall is you'll have to change out the tranny though. My buddy has a 300 L6 in his 84 F250 w/ auto 2wd never gets less than 18 MPGs on the highway.

 

Also prolly easy to come across a 300 L6.

 

visit the 335 engine forum...it's the most active engine forum.. You can get parts for a 400 that will give you far better than stock 460 performance and better mileage. 2v quench heads from australia and pistons from sponsor TMI that are designed for them give incredible quench and performance.

The 400, which was plagued by decompression at the onset has become a rel jewell of a motor recently though most ford nuts are ignorant of the advances and advantages in it's design. SOme are getting about 15mpg on 350+hp engines that pump out 450ftlbs of torque...probably quite a bit more than your 460.
I'm building 2 400's that I'm betting will beat the wheezer I built for mileage and the 400's will be far more productive.

 

Also theres apparently 8 400 block entries in the enginemaster comp after the first 400 placed in the finals by a family team last year.

 

Maybe instead of spending a bunch of time, and money trying to obtain a very minimal change in MPG, that would take way to long to realize a difference to justify the expense, why not buy another little throw away car that gets the mileage you are looking for. If this is daily transportation, you will see your money back in no time, and you wont have to take your truck apart.
How much are you going to spend on a new engine combo, and how much gas are you going to save VS. the amount of time it is going to take to offset the cost. Could take years. Another little ride would be immediate.

 

If you are really into downsizing I woudl go with the 300 I6 If not then I would listen to what banjo has to say and add an gearvendors overdrive to boot. our trucks have lots of throtle and accelarate a long way droping the rpm will help on saving gas. these trucks were designed to crusie the highway at 55 the not 75 you can probally see more mpg by droping the speed. which I dont want to do so I am looking at an overdrive. let the enging spin 22% slower and go faster.

 

I'm not sure if your truck is 2wd or 4wd, but to downsize to the 300, would be quite an expense, and you won't see the mileage gains you are looking for. I love my 300 and wouldn't swap it for anything, they are great motors and last a long time, but these are heavy trucks (especially yours being a supercab), and the 300 would have to work pretty hard to push it down the road. I've heard claims of 18 - 20 mpg with a carb'd 300, but realistically, I get 11 - 12 with a 4spd. I understand mine isn't stock, but if you go to the 240 - 300 six forum, and search for fuel mileage topics, you will get a better picture. I think that properly tuning your engine, a camshaft and timing gear change, you can improve your mileage. What type of exhaust system do you run?

 

theres a reason why ford put the 300-6 in 3/4 and 1- ton trucks and not the 302 V8. The 300-6 with very little money can be made to make very decent power and make upwards of 17mpg. My 300 has the Crane Truckpower cam, shaved head at 0.060" mild port and polish (did myself) and EFI exhaust manifolds. I dynoed at 175hp and 335 lb-ft of torqu at 1950 rpm, i also get 17 mpg around town on 35" tyres and 3.55 gearing. If you are serious about a six check out www.fordsix.com you want to see true hotrodders and ****loads of info check those guys out.