happy new year every-one
i have been reading and searching the net on how to modify my 351m but all i came across is that it's the lowest hp motor out of the bunch what should i do? it is stock right now with dual exhaust thanks jer

1977 f150 supercab
351m c6 tranny
long box 2wd

 

Maybe give some more info one what actually you are looking to do (like gain a bunch of HP). Budget comes into play also.

 

go to the 335 series forum, on this site, and read away. I've been reading this link with great interest. https://www.ford-trucks.com/forums/5...-the-dyno.html

 

go pick up the latest edition of HOT ROD magazine (think its still the latest) has a deuce roadster, 57 chevy, and 67 camaro on the cover. they do a buildup of a 400, but it could kinda be made to apply to a 351, i found the article interesting

 

well i would like alittle more horse power not shur what it's got but my plans for the truck is a worker but like to play abit too

 

Because this is specifically an engine question it is best asked in the engine forum relating to it.
The 335 engine series forum is FULL of info.

If you have 73-79 truck questions that aren't systems specific ....head back to this forum

There is also a article section that has an article about the 351m/400

https://www.ford-trucks.com/article/...00_Engine.html

 

Agree that you should go to the proper engine forum. That said, I've always heard that the 351/400 Modified motors were the best kept secret in OEM motors ever. They have a very favorable rod/stroke ratio, which gives you lots of high compression options. Please, please read the 400 buildup article mentioned earlier. The big downside to the modified motors is that they had every smog option known to man on them. If you build them, they will rock the competition. The 351M has some serious potential with the high rod/stroke ratio.

 

It's good to see that the potential of the 351M/400s is becoming known. Fortunately, there are still enough people who consider it a boat anchor or who will opt for the 460 that they are still plentiful and cheap at the junkyard!

A mind rebuild with a 400 crank, aftermarket manifold/carb and a mildly aggressive cam will net you more than enough power for a daily driver and won't cost much more than a stock rebuild. Trust me, you will not be disappointed.

 

There was another discussion about the M motors earlier, about why they got such a bad rap. What was said before was that they were the emissions poster-child, with exactly zero horsepower because of it, an in an effort to increase combined average fuel economy, Ford started putting the M motors in heavy trucks that would have otherwise gotten a 429 or a 460, and the smogged, strangled and decompressed 351/400 just got worked into an early grave.

I heard that due to the rod/stroke combination, even mildly built engines don't need more carburetion than a stock 2150 carb (great driver) and the 2V manifold is actually pretty good for what it is. Just a mild cam, maybe some more compression, some tri-y headers, and you've got a stout motor with great driveability.

 

There's something to be said about the 351M/400, that around my parts, you can get one for $50, when a 460 is about 10 times that, yet build one up pretty well, and relatively cheaply.

 

this might help? Just put a rebuilt 400 in my 79 had the valve seats hardend the were shaved .010 block bored and line hoend stock compression piston 8.5:1 balanced edelbrock intake and 600 carb one step up from stock melling cam and headers into a 21/2" single exhaust. It will bark 38.5s w/locker engaged and 4:56 gears plenty of power for such a mild piston cam setup. By the way as long as I keep my foot out of it and 60 or less still gets 12 mpg.

 

Acutally i found that a big big on a 400 with a good 4bbl along with a set of headers/exhaust, then a straight up timing set with the timing set straight up, and you have a very strong motor. Because of the big heads, opening up the airflow with headers intake and carb (the timing thing just makes it run so much smoother and snappier) its not uncommon to see gains of 40-50hp, i know these the same mods i did to my 400, and i gained at least that amount, and i get people coommonly asking me if I'm running a 460.

 

They are basicly good motors but I would for sure find a 400 crank. I went through a 400 in a 79 3/4 with 3:55 gears with a T-19. I was getting around 12 to 13 MPG and after I went through the motor I am getting 17 to 18 MPG. That isn't running hard though.


I had the block checked, cam and crank line honed. The block had to be decked but what I did was to put the biggest valves that can be put in one of those heads. I set the lifters at .010" preload. The cam is has a lift in the low 5's with a mild duration. I put a Performer intake with a Holley vacuum advance 600. I also put the pistons in backwards. I can't run regular unleaded but I am happy with the fuel milage. The trick is that the most volumn metric efficient you make a motor the more it can do with the fuel you put in it. I didn't increase the fuel I was giving the motor before I went through it but it is doing more with it now.

 

"I also put the pistons in backwards".

wazzat mean? thanx.

 

search the web for " sherman backward pistons ", there's an article but my pos won't open it.