We have an 87 F-250 SD 4x4 ex cab long box. Truck is in very good condition and is used mainly for towing landscape equipment and plowing snow in winter.
It is 460/C-6/4.10 and gets about 7 mpg. We bought it used, 105K mi, it had a just rebuilt 460 then, .060 overbore, .030/.030 crank, 2nd rebuild from new and machined to the point of no return. That took us to 154K mi when a Badger piston broke and that was that.
Found a 1986 engine, rebuilt the short block with all sealed power/arp, .040 overbore, .010/.010 crank, reused the blown engine heads and all was well untill 205K mi, ex valve spring broke and valve put hole in piston and the aluminum filings and valve head bouncing around killed any thoughts of rebuilding that one.
Now all the 460's in my boneyard are at the rebuild stage. Not to mention these carb engines are getting hard to find. Figure $2600-$3000 before being back on the road.
The boneyard also has a 1979 351M that was rebuilt but never ran(spare crusher engine) they will sell for $400, add cam/headers/intake/carb for $835 and go. They also offered a 1978 ford 400, rebuilt 4300 mi back with paperwork to verify this for $350, add that $835 parts list and go.
Seeing fuel is $3.65 here and we don't have the cash for an OD trans If I go to a smaller RV cammed engine will I miss the stock 460 that much or should I forget all this and visit the (different one than rebuilt the first 460) rebuilder again.
Thoughts anyone?

 

I'm not a big fan of the Boat Anchor M motors, however, the positives here would be that the motors you could get are cheap. And with gas prices the way they are, and the rest of the economy in the shape its in, going for a cheaper motor will probably be worth the hassle of having to do some fabrications to get it into your truck. I would get the 400m over the 351m. Put an RV cam in that to give it some low end snort, pull some MPGs out of her. I don't think you'll miss the 460 what-so-ever with a bigger cam in a 400.

 

I'm a fan of the M motors. These were great engines, designed during the Total Performance era, but because of political reasons never saw their full potential. Between the long stroke of the 400 and those wonderful Cleveland heads these engines have the ability to grunt down long and breathe well on the top end. With the restrictive intakes and exhausts, retarded cams and uninspiring compression ratio these engines had no choice but to go down in history as smog motor lumps. By addressing these four concerns, the 400 is one of the easiest motor to join the 400+HP club.

Normally I wouldn't be for one of these swaps. I would say stick with what you have. But considering you can get a good 400 core at a good price then I say go for it. That is, if your local laws allow. Most states will have laws on the books saying that you can't swap in an engine older that your chassis.

Get the 400 over the 351M. Though there's nothing wrong with the 351M but the 400 will make considering more torque. Stab a "RV" cam in straight up (check and double check to ensure the cam wasn't ground retarded and the timing set is really a straight up set), use full length headers with the smallest primaries you can find, and use a dual plane intake topped with a vacuum secondary carb with a MAX size of 600cfm; preferably a touch smaller. These mods will maximize the low end on this engine though it will cost you a couple ponies up top. Unfortunately there's not much you can do about the compress on the cheap, that will take either a head or piston swap, but for what you're doing a stock long block is fine. With this combo you may miss the brutal power of the 460 but the 400 will match it with ability. It will do everything the big block will do.

On a side note, it seems you have had a few premature total failures on you rebuilds. I would be looking into that. Something isn't right. Maybe the machining, maybe the parts choice, maybe the assembly, everything needs to be check. I good rebuild should wear like a factory engine or better. Something is wrong.

 

My 400 in my 78 F-150 got better mileage than the 351 does in my 88 F-250, and the F-150 weighed 100 pounds more (according to the scales at the scrap yard.) The 400 has a longer stroke than even a 460, so it does really well towing.

I had a Edelbrock Performer and carb, a Lunati Truck Avenger cam and long tube headers.

 

You have to be kidding! Both the 351M and the 400 after 1974 were smogged up turds that were very prone to cracking cylinder heads.

Neither one will get any better MPG than a 460, 351W or whatever, because these trucks have the aerodynamics of a brick.

FoMoCo's "Total Performance" era occurred in the 1960's.

By 1974, the hipo era was over, killed by Gov't agencies that demanded automakers make vehicles more fuel efficent.

Most 351M/400's came equipped with smog pumps, all came with EGR valves (after 1972). All were only available with 2V's, some used the horrid variable venturi carbs.

351M: 1975/79 FoMoCo Passenger Cars / 1977/79 F100/350 / 1978/82 Bronco / 1980/82 F150/350.

400: 1971/79 FoMoCo Passenger Cars / 1977/79 F100/350 / 1978/82 Bronco / 1980/82 F150/350.

 

While I do not agree with the Total Performance statement either, the venerable 351M/400 did come along at a very dark era in automotive history. They are blessed with the coveted Cleveland heads, but they did suffer from other design flaws. Yes, the 335 series engine can make some good power, but in the Op's situation I would look for another 385-series 460 to rebuild.

I had a 1978 F150 (4X4) with a 400 that I rebuilt 21 years ago. When I got it, it ran on 6 cylinders. After a good rebuild with an Edelbrock cam/intake/carb. as well as other items for a complete rebuild that truck ran like a top. 21 years later that same truck is sitting in my neighbor's driveway. It still runs as good as the day I backed it out of the garage when I rebuilt it. The 335 series is overlooked, but it is a darn good engine IMHO. Is the 385/460 better? Perhaps, but if I started with a 335/400 I would stick with it.

My first 1978 Ford truck, a F250 4x2, had a 460 in it. That thing was a beast. I had it tuned on a chassis dyno after I had a custom dual exhaust installed. That thing was a stealth truck in vanilla clothing. I blew away a few Honda rice toys and a few 80's era Camaroes from time to time. I still got 14-15 MPG at a sedate 60 MPH unloaded. Remember when the national speed limit was 55 MPH?

 

I'll just say that the machine shop that rebuilt the 460 that came with the truck either did it on the cheap or had not a clue on how to R&R a Ford product. A dropped valve cause the demise of the bottom end we rebuilt, and those heads were rebuilt by the machine shop that doesn't have a clue.
IMO the Cleveland M block engines have alot of unused potential. I owned a 71 Torino with a 4bbl 351C 4spd and it was far from slow by anyones standards. The M blocks are just a tall block version of this and with a rv cam, wieand intake, holley 600 carb and summit headers should be strong, and with less cubes should be better on fuel IMO.
We also have a 1985 F150 plow truck with 351W/aod/3.50 ish gears. It is way better in fuel when plowing snow or driving around. We do not use that truck for towing as it is to light duty.
There is no I/M emissions here beyond the catalitic converter thing that says if it was made with it you have to keep it on there. The 87 had no cats so no problem there.
The 460 was great for towing but when snowplowing (9'6" blizzard wide out plow) even with firestone winterforce tires was less than ideal for traction in the snow.
We actually do more stop and go city driving, the hwy is just the 65mph bypass to get from one end to the other. Thats maybe 20% of all the miles.
This is a daily driver work truck and fuel use is important also. All these things are on my mind trying to figure out the best way to do this.

 

351C shares some parts with 351M/400, but the comparison stops there, especially if it's the 4 bolt main 351C Cobra Jet.

From 1975 thru circa 1984, I passed out over the back parts counter, over 400 sets of 351M/400 cylinder heads to mechancs.

That's one partsguy at one Ford dealership, now multiply that by 6,000, the number of US/Canadian FoMoCo dealers at that time.

The heads cracked, usually after the 2/24 warranty expired. The replacement costs to the suffering owners was SEVEN HUNDRED DOLLARS parts and labor, a lotta money back then.

If you were around back then, worked at a FoMoCo dealer, had to face screaming customers that had near new vehicles, I rather doubt you'd love these turds.

 

The 351C I had was NOT a Cobra Jet variant, just a 4bbl dual exhaust variant. I bought that in 1978 and sold it in 1984, other than tune ups it withstood my 17 yr old driving habits.
I worked at the Chev* dealership at the time, when chevy left Ringle Chevrolet became Ringle Auto Service Center for all makes. That lasted untill 1985, when I started our business.
Biggest headaches I ever saw regarding the M motors around here was bearings. In all fairness these bearing problems were on vehicles which had very poor maintainence. I have never owned an M motor yet.
I look at the head cracking problem and it makes me think if either of the boneyard motors have had this problem they have been replaced allready as this is 2012, the 400 motor has 4300 miles past a total R&R and the truck was wrecked in an accident in winter 2010. If the heads were going to crack would they not have done so by now? If they did they should have been replaced. Or for $700 was Ford just putting on another crack prone set?
I do love the power of the 460 when towing, Don't get me wrong. What bothers me is the 7 mpg it gets. Our 95 Dod*e V-10 got 10 mpg doing the same things, Our 95 Che*y 4x4 Dually has a 1971 427 TD motor in it(easier to fit than you think) and never gets less than 10 mpg doing the same things and should get around the same milage.
It really comes down to If we put another $3000 or so doing another 460 and only get 7 mpg it's going to be hard to justify keeping this nice truck which I like in the fleet.

 

No kidding, Bill. I would expect better from you. The 400 came from the same time and the same minds as the Cobra Jets, Boss and Cleveland engines. Just because it was first installed in a production vehicle in 71 doesn't mean that it was designed in 71. They had years of R&D beforehand in, guess what, those same magical years that produced some of those wonderful engines of the 60s/early 70s. Now was it suppose to be a performance motor? Well, I wasn't in the design studios back then so I don't what they had planned. But think about this. The 331 and 352 FEs started out as just the Ford V8 in their big sedans but a few years later they spawned the HiPo, "Thunderbird" V8s, PI, Multi carbed 390s and 406s, a dozen or so versions of the 427 and, of course, the Cobra Jet. Not to mention the race spec motors that ruled every sanctioned body they were allowed to compete in. The 221 and 260 Windsors started out as an economy V8 for the Fairlane but what did they turn into after a couple of years? HiPo 289, Boss 302 and, again, another hand full of racing engines that ran and won in every type of competition they could enter. And what about that lonely lump of a Lincoln motor? It turned into the Thunderjet, the new Cobra Jet and the Boss '9. I don't know what Ford had planned for the 400 but I do know that there were prototype 4v intakes floating around. This leads me to believe they had something up their sleeve.

Unfortunately, the timing for this engine was terrible. The new government mandated emission requirements took over and Ford had to scramble to get their engines to meet them. That's why we had to suffer through low compression, retarded cams, soft timing, smog pumps, restrictive cats and such. Ford had to go back to the drawing board but it couldn't do it fast enough and had to make the engines that they had work. The 460 and small block motors of the 70s and early 80s had the same treatment. Nobody brags about how fast their 302 powered Mustang IIs were. They had the same 302s that had powered the Mustang back in the late 60s but, to meet emissions, they had restrictive heads and low compression, weak cams and timing and terrible intakes and exhaust. The only difference is they had was the performance legacy from before that carried them long enough to be treated to the new technology that came about it the late 80s and early 90s. The 400 had no choice but to go down in history as a smog era slug.

Those were dark days. Hell, it was these government requirements that put the American auto industry into catch up mode for years and almost bankrupt, not only Ford, but all American manufactures (Actually look at GM, AMC and Dodge from those years. They all were hurting and we ended up losing one of them). The tech wasn't available to meet the new regs and give us the performance we wanted. Something had to give and it wasn't going to be what the tree hugger wanted (On a side note, this was also what gave the smaller, cleaner, and more fuel efficient imports a foot hold here). But as tech evolved so did the engines. It wasn't until just recently though we have been able to buy engines with the performance we want and still meet the government requirements.

But back to the subject, The 400 had the potential to be great. I don't think many people would argue that the Cleveland was made to be a high performance motor from the start. Yeah, there may have been some compromises made on production models but it was conceived from the start to be high revving and deep breathing and used the best tech of the time to make great power from its displacement. The 400 was also based off of this. It's obvious from the longer stroke (one of the longest used on any Ford engine) that it was meant to create a ton of torque. But by the use of the Cleveland head it would seem that they were trying to have their cake and eat it too and make good HP on the top end too. Today, with what we know now, the 400 is a sleeping giant wanting to be awakened. Do what I said before. Open the intake and exhaust, increased the compression with flat top pistons or closed chamber heads, stab in a good cam and enjoy your new 400+ horses. And do it while knowing you have an engine a lot of people would just throw away.

 

Well I can only account for my own experiences. My 351M power 78 F150 has well over 200K on the original long block and it's still going strong. The truck had been setting in a fellow's back yard for ten years when I bought it. I put a little fuel in the carb and the truck fired up and drove onto the trailer. After changing the oil, plugs and wires and a little tuning to the carb and I drove it from Charlotte NC to Tampa Fl while pulling my 98 Ranger in the middle of summer. Over 600 miles and other than having to stay in the truck lane on some of the longer grades in I77 it performed great. After driving it for a few months like that I stabbed in a better cam with a straight up timing set, put on true duals with glass packs and high flow cats (I had to), and topped it with a Weiand intake and a 470cfm Holley Truck Avenger carb. This woke up this truck like you wouldn't believe. I can't wait to swap out to a 400 crank and flat top pistons. As of now I can smoke just about any new truck on the road.

Also, my father bought an old 1 ton roll back with a 400 in it. This poor truck had worked its whole life and had been poorly maintain. It showed a lot of miles and was smoking. Well, he pulled the heads for new guides, seals and a valve job. I don't think that's bad for the age on the truck and the work that it has done. After the head work the truck has been running like a top with the original short block and has pulled and hauled every load that my old man puts to it. And my old man ain't easy on trucks...

Of course I know a bunch of farmers, rednecks and hillbillies (I’m related to most of them) that still run these engines. Some are in different states of repair but they still keep going. My father also had one of those mysterious 71 "high compression" 400s in a LTD. From the tells of my youth that thing could hang with all of the old big block Galaxies still on the road back then. After I drove, and came close to buying, one like it in high school I believe it (it was sold out from under me; $300 was a lot of money to round up back then ). I'm sure there may have been problems when these engines were introduced. That probably goes back to they weren't designed to begin with for the emission equipment they were saddled with. It seems to me though the ones that are still out there now must be survivors.

 

My 400 hasn't had any problem with cracked heads in 12 years since its rebuild. It was also dynoed at 375hp and 450 lb ft of torque.

 

Now, if I go with the 400 does anyone have a good RV cam recomdation for it? Dual pattern/single patternor?

Thanks for all the help also.......

 

I reemeber those 400M engines, most only got about 8MPG & didn't offer the power of a 460.
however if you can get one cheep ....maybe roll the dice & see what happens.

good luck

 

I used this in my 351M.
Summit Racing SUM-5200 - Summit Racing® Camshafts - Overview - SummitRacing.com
I found a NIB one on Ebay for $25. I wanted something a little hotter but for that price how could I pass it up. It's very mild but it may still be a little more than you would want if you're going for max lowend and MPGs.