If anyone in Texas wants a running 460, I'll trade you for a running 400.

 

HA HA Alex...Great job. Very informative and well stated!!!! Thanks for the effort you put into that. Though I hadnt given it much thought in the past, I really need to see what I want to do for my upcoming build. Truck has a 351m with mild performance upgrades....

 

Most of this thread is hearing the good points about the 351m/400 so I'll play devils advocate and tell you why I don't like them, and I have posted all this before.
My uncle farms and for years he had license on four 77-79 Fords at all times. And they weren't just the same trucks, they rotated. I'd say he's had over 30 total and probably currently still owns 10-ish though most are getting to be in pretty sad shape. I'll get back to his trucks though.
In 1980 a local farmer bought a brand new left over 1979 F-250 full time 4x4 with a 351m. He stuck a bunch of money into the truck right away, Cobra AM/FM/CB radio, brush guard, roll bar, turbine wheels etc. He had one 351m replaced under warranty, I think around 1981. By 1984 it was in a cow pasture needing another one! That's when my dad bought it and tried the main, rod bearing and HV oil pump trick. He probably drove it for 6 months then dropped in a junk yard 429 that he got for $75. The 429 also has the worst heads ever, the D2's. He did put a straight up timing set in it but kept the stock intake and exhaust manifolds. The truck straight up ripped. Gas mileage also increased from 7mpg with the 351m to 9mpg with the 429. We still have that truck and 27 years later that junk yard 429 is still running great. Two brand new 351m's didn't even last 4 years combined.
I bought my 1977 F-150 in 2005 with a 351m. My cousin and I figured the oil pressure gauge was not working since the needle was not moving and it did not knock. Nope! It really had no pressure! If I started the truck cold and then revved it to about 3 grand the oil pressure gauge would move about 1/64 of an inch! It also had low power and I found almost no compression on one cylinder. 20 years earlier my dads 79 had the EXACT same issues. I built a 460 and never looked back.
Now back to my uncle. Since he's had about 30 of these truck I obviously can't touch on them all but I can tell you out of 30 of them I'd say at least 10 351m/400s have died. All of them have oil pressure problems and a good number of other burned the valves then combined that with horrible mileage and no power. I'm not seeing too much good about that! haha.
My uncle bought a 1978 Ranger full time 4x4 400 in around 1988/89. Him and my dad took it on a LONG test drive to make sure it was good and hot and the oil pressure would be ok. During the test drive everything seemed ok so he bought it. By the time he got home it had no oil pressure! He installed new main bearings, rod bearing and HV oil pump. And to this day it is the last 77-79 that he has license on, its still going! It is guttless though. I'd say top speed is around 75mph. And to drive it through a ditch you have to use low range and it still almost gets stuck from lack of power, can't turn the tires on dirt in low range!
My uncle also bought a 1977.5 F-250 4x4 351m 4-speed in 1982 with a bad engine. Only 62k miles on the truck. He swapped in a 400 from a 1971 LTD, which is the non-smogged holy grail of 400s if there is such a thing. He actually never lincensed the truck and he gave it to me for awhile but I gave it back. It still only has 62k on that truck and still has a 1982 license plate on it. Two points to this one. 1)Another M only made it 5 years/62k. 2) The holy grail of 400s with part time and stick didn't hold a candle to my dads smogged 429 full time auto! I know this is hard to believe by some since I've mentioned this before but I sware it to be true and we still have both trucks.
I will admit my uncle did buy a very nice 1977 F-150 4x4 351m auto and it had headers, timing set, cam, and 4 barrel. He didn't have it long because someone saw and it and asked to buy it, but it did run pretty good. But I'm sure if he kept it, it would have lost oil pressure and compression. lol.
I'll just stop here as I think this is sufficent but I could probably add about 20 more 351m/400s to this list as all my dads friends drove these truck back in the day as well and had all the same problems. I know my uncle has done mains, rods and pump on at least 5.
So these are just a couple reasons why I don't like the modifieds. I actually hate them.
I think I'd rather run a 350 Chevy in my truck!
This is just my opinion and no one can EVER change my mind just as those who do like them will continue to like them and thats just fine with me! For awhile (5 years?) I think I was around 3-4 351m/400s dying every year! How could anyone like them after that. And when we are talking all these trucks it can't be a freak occurence. Of course I do read about the same things on the net constantly so its not just me.

 

More than likely if they were dying and had lack of oil pressure, whoever "rebuilt" them didn't know what they were doing.

 

They were built by Ford. Most of these were lower mileage and purchased fairly new in the 80s. To my knowledge none of these had ever been rebuilt. And most of the time it's easy to spot a rebuilt engine based on paint, sealer/silicone, freeze plugs, gaskets, cleaning, upgraded parts etc. None of these engines showed any signs of this. I bought my truck in 2005, it died almost immidiately. It also showed no signs of ever being apart. Yes it was old at this point but didn't have super high miles at 140k but it still followed the very expected trend (expected by me) of crapping out in very short order. It didn't surprise me one bit.

 

My 1978 4x4, original 400, 200,000+ miles, performer intake, 570 4 barrel carb, strait up timing, 3.50 gears, 35 inch tires, main bearings grooved all to heck, leaks oil from the rear main because the crank is warn down at the seal, and with a light foot, gets 12 MPG mild stop an go. Still pushing oil over 30 psi hot, and puts me back into my seat hauling a bed full of scrap. Guess I was one of the lucky ones. However, over 60 mph, MPG goes out the window. It's all about how you drive for halfway decent fuel economy. But the majority of us owners didn't buy these trucks for fuel economy. I have a 38 gallon fuel tank, and it hurts to fill it up, but at least I get to drive a sweet old truck.

 

I've had about the same experience. Everyone I know who ever had one suffered from low oil pressure at low miles. Obviously not all 351m/400 are turds itching to die, as some members here and elsewhere seem to have one with higher miles not suffering from low psi, or like Ranger429's which I bet is pretty stout, but I'd say 85% of the stories I've heard have been bad. With that many first hand accounts I just stayed away. And now hearing about people performing the oil psi "fixes" and still having problems..no thanks for me. As far as MPGs go..thats what my Sentra's for.

 

Well I didn't intend for this to be a 351m400 vs 460 thread.Of course a 460 is stouter.But my old truck won't really be used for extreme conditions anyway.As far as oil pressure goes so far so good on mine.I still have about 60-75 pounds warm at idle.I will admit that I believe the engine is pretty fresh.Very clean motor clean exhaust and sounds like possibly a very mild cam along with all the external stuff mentioned before.thanks for all the input.

 

Having owned and driven 2 351ms and 1 400m over the past 4 years, all with over 100k (one wrecker might have been 200K!) and all original engines I've never had a problem with oil pressure. The trucks were two 77s and one 78.

My 78 (351, C6) towed over 8k lbs at one point without a hiccup. And yes it cruised at 65 down the highway, granted it took a bit to get there; but it was a stock truck.

From what I recall my dad telling me, oil changes weren't really that big of a deal back then. I wouldn't look to the engine to blame, I'd look at owner maintenance. No new engine should fail that quickly unless there was something seriously wrong with it (say bad oil pump) from the factory; but if that was the case it most likely wouldn't last a year.

 

Theres nothing unusual about a 25 yr old engine dying at 145K miles (as you admit), thats probably why the guy sold it. I have had two M engines and while certainly not impressive, they ran fine and gave no problems, other than lousy gas mileage. I have known numerous friends and relatives that had these engines in vans , cars and trucks and its not like they were known as a "bad" engine, my cousin put 150k miles or more on his '79 before he traded it, still running strong but he wanted better economy.

 

You must be talking about the people who built them at the factory, 'cause I am sure he was talking about the new ones.

 

my buddy has a 78 351m with 400 heads or possibly a 400m motor.... but he drove our 360 FE and said they have about the same power and his 351/400 is a very stout motor... that aside, i think the FE's were a bit stronger motor than the Modified's

 

A stock 360 is no powerhouse either, it was a destroked 390 low compression engine plunked into the f series. I dont know why Ford bothered destroking the 390, if it was economy they were after, they failed miserably. That said, its still a good running reliable engine.

 

Wellllll I think whoever's watching ceeertainly has a taste of both sides now haha, and Blown 331, I totally see where you're coming from, honest experience is honest experience, and although many people's "experience" is just based on perception (if you think it's going to be gutless, it will be), with as many examples as you've had, I'm sure you would give a good engine credit for being so. And that said, I just today tore down my 3rd catastrophically failed 400 engine. Both of the last 2 have failed because of builder error (me being one of the builders haha, but hey, I'm learning, and I love it), but the first 2 did have horrible oil pressure as soon as they warmed up, and I too have wondered if the gauge was just broken, and the 2nd did eeeeeat it's crank in pretty short order, but, the 2 I've had with 2V heads have pulled like locomotives. I pulled out pine stumps with the first one, bone stock from 77, and none of the 3 have ever dissapointed me with a burnout when called for. The debate goes on, even in my own garage.

Hog creek, woops, didn't even notice that haha. You'll find out pretty quickly that when you even hint at the 400 and 460 being in the same thought, people will begin to sing the praises of one, implying the inferiority of the other, and then you have a war haha.

Anyway, I'm using the shortblock of my most recently dead 400 for a fairly conservative build right now, and it has GREAT oil pressure, 70-75 HOT, at about 40-50,000 after the last owner rebuilt it, so we'll see what it can do for me down the line, and add that to the great 400-460 evidence log.

Back to the grease for now, AleX

 

haha I love the honesty. Most people would just omit that little bit.