Folks, this is my first post to this forum so I appreciate any help I can get... I have a 1986 F-250 with the 351 engine, 4-wheel drive, automatic transmission. The engine is about to give up the ghost and I wanted to see about replacing it with something with a bit more power, like maybe a 460. I use the truck almost exclusively for hauling, towing a boat and hauling a camper so the more power the better. What would be involved with swapping out the 351 for a 460? Is it insurmountable?

Also, I need to replace the bed. Rust is rampant and the bed itself has split. I can't find a decent replacement anywhere, though. All junkyards have beds in worse shape than mine. Any suggestions or any place where you can get aftermarket beds?

Thanks.

 

with the 460, i dont know if you can install the fuel injection on that thing. and you might not be able to bolt it to the transmission. im not sure what transmission is in that, cuz i have a C6 with a 460. plus you might have to get new driveshafts, because of the lengths.

 

If it is a 351M you dont have to trade the trany.but you will have to use the mounts that are on the 460.For the beds if its just the floor or any part your local auto parts suply store will have them and if not you could but a nice wooden floor in it made of oak or something nice anyway hope it helps un till some of the smater guys on her have a chance to answer you

 

You will need to change the mounts on the frame for the 460, I have these on a frame right now. You will need to change the radiator, I also have, maybe core support. You will have to change transmissions as the 351 tranny is different than the 460. Those are the main things, there's always other small stuff involved in these kind of swaps. Where are you located? I also have a pretty decent bed for sale.

 

Thanks for everyone. The bed is pretty much shot through and through. It has the usual rust above the rear fenders, but it is pretty bad. Eaten all the way through on both sides. What's worse is that the bed actually is "torn" lengthwise on the left hand side starting at the back end and extending a couple feet toward the cab. If you grab the left rear of the bed where the tailgate latches you can pull it sideways a good 6" or so. I could probably get it welded but with all the rust damage I figured I'd just get a replacement bed if a decent one could be found for a reasonable price.

It is not fuel injected. It is carbureted (Holly 4-bbl). I can still work on it, thnk goodness. As for the transmission, it is a C6 (I checked the codes) but whether it is the same C6 that would bolt up to a 460, I don't have a clue.

85IDIDiesel, I'm in Colorado. What type of shape is the bed in that you've got? Right now the bed is probably the most pressing issue. The engine has some life left in it but I wanted to start getting info for the swap when it does die.

Thanks again everyone.

 

The bolt pattern on the 351M is the same as 460, so you wont have to find a new bellhousing for the swap. As pointed out, you will need new motor mounts, as well as supports, if memory serves.
Depending on how complete a 460 you find, you may also need all the brackets for the front of the engine, since none of them will change between blocks. You will definately want improved cooling, you will need a heavy duty radiator as well. The exhaust will need to be replumbed for a short distance from the exhaust manifolds (headers may or may not empty to the same location, if you have them). The transmission crossmember may or may not need to be adjusted (although the correct motor supports should place it in the correct position), and if so, you will have to trade driveshafts.
That should pretty much take care of the swap, although you may want to think about heavier springs in the front for the added weight of the big block.

As for the bed, seems like what you are describing is the bed floor seperating from the sides... There is a joint there between the inner bed panel and the floor, you may get by with reattaching the bed sides, and hold out for a new bed. You can get all new parts for your bed from National Parts Depot.
Also, if you arent too worried about the 'correct' parts for your truck, the bed from a '87 up model is basically the same, just the wheel cutouts are rounder, and the bottom edgehas a smoother look than the '80-'86 trucks. It probably wouldnt be enough for the average joe to tell a difference.


(As for my 2 cents.. )
As for the engine swap, with gas prices being what they are, I would probably go for upgrading the 351M with some new performance parts when it needs rebuilding, hi compression pistons, hotter cam, etc. (if you are at any altitude in colo, you could really benefit from more compression over stock, anyway.) If you havent done it already, I would also get a shift kit put in your C6, and switch to type F trans fluid, itll last much longer, and hook up a lot better, too for all those towing duties. When all is said and done, you may end up spending about the same or a little less than the swap, unless you already have a freshly rebuilt 460 on hand.

Hope that helps

 

Your truck being an 86, I would assume it had the 351W. I thought they stopped using the 351M/400 in the early 80's. My 80 bronco had a 351W. Correct me if I am wrong(which is a possibility). If you do have the 351W you will need a new C6 because unlike a C4, the bellhousing is not removable, and your C6 has a small block bolt pattern. I would be more economical to rebuild the 351 with a better cam and such to get it to perform the way you want, but the 460 swap can be done.

 

The truck has a 351W HO, the M was killed off mid year 1982. Anyhow other than the engine and acessory brackets, you will need a new transmission, engine mounts and stands, and of course exhaust. If the truck is a F250 HD(Over 8500 GVWR) it probably already has the 3 core 460 rad. Basicly, your best bet would be to find a donor truck from which to take evrything you need, I've found a few little things that are oddball about my factory 460 setup compared to smallblock setups.

 

True about the 351W .. guess I was stuck in the '70's on that one

I would still go with the original advice about building it up instead.. the 351W engines can make plenty of horsepower.