I am looking at a '79 Bronco, and it has a blown 460. I have a 351M in a '78 pickup, and I was wondering if I would be able to do a direct engine swap.

Would it be worth my time to attempt this? Will a 351 be able to move a 79 bronco, and not put too much stress on the engine (the 351 has a .030 overbore, and a 650 cfm carb)?

 

you will have to change out the frame towers and the exhaust y pipe.

But if you sold your 351m and got another 460 to drop in you would have less time into the change out.

 

I was wanting to go with the 351 (or even a 302) because I am worried about fuel economy. I also have a '79 camper special with a 460, and I can't afford to drive it to school every day

 

The 460 will still do better than either of those other two. The "modified" engines were emissions de-tuned terribly from the factory and the 302 will rev its fool head(s) off trying to drag around the heaviest Bronco Ford ever made.

 

So even a 400M wouldn't be worth it?

 

Are you sure its a 460? it was never a stock option for those years.

 

both the 351m and 400 have potential but money must be tossed at them. in stock trim they are best used as boat anchors . the 400 of course is better of the 2 options but i dont recall that motor being stock in the bronco either.

a 302 would also require a different tranny, custom or modified motor mount/towers etc..

 

The 351M and 400 were used on those model Broncos. There was a nice article on a relatively inexpensive build on a 351M, under $2000, it ended up having 383 hp.

 

That 351m is a smog motor with low compression and while it'll get the job done all bets are off as far as gas milage. A simple cam upgrade should uncork some power and potentially increase milage.. as long as you use an RV grind.

 

The 351M is a detuned motor of the 400. There are kits to make the 351M into a 400. But they both came stock in the 78-79 bronco. I owe a 78 with a 400 and with some mods it has alot of power. But both are not very good on gas. So in my opinion going either way wiht a 351M or 460 is the same gas except for the power of the 460. And trying to go with a smaller engine on a big bronco no good. This is just the way they were made, powerful and gas guzzlers.

 

The 351M and the 400 were the ONLY stock options offered for the 1978 and 1979 Bronco. The 460 didnt come in as stock until i believe 1983 after they ended the 351M and 400 in the 1982 model year. People by far under estimate these two motors. I mean they didnt even come stock with a 4bbl. a good 4bbl intake, cam, headers, replacing the retarded cam timing set with a trued cam set and ofcourse junking all the smog crap and you've got a motor to be reconed with. Ive got a 351M that I am getting ready to build up to put in my 1994 f150. And ive heard of guys getting anywhere from 12-18 mpg (like 8-9mpg stock) with these motors with 400-500tq, just as good mpg as any 460 and almost as much tq as a 90's powerstroke (514tq) but the M block weighs 80% the weight of a 460, another thing to consider in choosing between the two, less front end weight.

 

351M is not a de-tuned 400M its a smaller cylinder bore hence the smaller displacement. The 460 was never available OEM in the Bronco. However, it bears the same transmission bell-housing bolt pattern as the 351M and 400M so making the swap to it makes sense if you don't want to have to adapt or swap transmissions in the truck as well as the engine. If you swap to anything but a 460 from the 351M or 400M you are looking at either adapting (if they are available) to fit the original transmission that was behind those engines or you have to drop in a 460 which needs no adapting. The 460 also has a few things going for it that the 351M and 400M don't. Better emissions systems integration, electronic fuel injection, basically all of the things that having been produced for far longer than the other two engines would have given it.

Would agree that the 351 and 400 can be "woken up" but at the cost of swapping in a newer power plant that was produced longer (future parts availability) and benefits from the application of technologies that were not only never employed on the 351/400 but never will be, it would just seem to make more sense to employ newer technology rather than trying to infuse better performance into engines that require so much modification to get it. Just my take on it. To each his own. Best of luck however you choose to proceed.

 

351M=3.5" stroke, 400=4" stroke, have same everything except pistons and crankshaft.

Anyway, if someone went through the expensive trouble to swap a 460 into your Bronco, it would probably make the most sense to put another 460 into it. Otherwise you are looking at having to find all of the parts to "unswap" the 460 to fit the 351M in. That, to me, would be a step backwards. And I'm a 400 kinda guy.

FWIW, I put a 300 6 into my '79 Bronco and the gas mileage ain't all that great, but it's still considerably better than a 460 or 351M. And that was with all stock parts.

 

The 351M was a 400 with a shorter throw crank. Therefore, the only thing different between the two internally is the crank. And I have a 351M that has been "woken up" with a 30 overbore, higher comp, ford racing cams, cold air intake, and all the smog controls have been removed (Reburner, erg, mufflers, ect.), but it's in a truck that I am selling.

Back to on topic, what about a lp or diesel swap? I am finding some early 420CID diesels and harvesters for cheap. Could pick up a bronco body and run all the correct lines, would be a sick bronc. I hear that the mid 90's powerstrokes are a direct bolt, with a radiator change. I think that would be decent on the gas milage. Strip the smog off...

 

Along with the shorter throw crank the 351m also has taller pistons to account for that. but ya other than the pistons and crank they are the same. deisel would be more torque and better gas mileage but ALOT heavier. I dont know if your going to use this truck for any serious off roading or not but if you are personally i wouldnt go diesel. the dry weight on a powerstroke, just the engine, is over 900lbs. but i cant say as far as the swap goes. someone else would have to chime in for that. I personally am going with a built 351M in my 94 F150.