Hot Rod Magazine built a 400M engine in their September 1998 issue. They got the motor to produce 380 h.p. and 468 lb.-ft. of torque for less than $2000.00. Not bad for an engine that came with at most 173 h.p. in it's stock form. I am in the process of doing the same thing to my truck.
Mike

 

Look under 'technical articals' on this site. There is a great write up on 351m/400 which will
give you a lot of usefull information.

 

Good thread and good info... Thanks !

 

You realize this was 1999?

 

Well that`s what it is here for !

 

The 351M and 400 have exactly the same oiling and bearings, they share blocks .... same bore, same heads, etc. The difference in a 351M and a 400 is simply the crank shaft and pistons.
The 351M has 3.5" stroke while the 400 has 4.00" stroke. That means 1/4" extra on both side of the crank, 1/4" lower at bottom dead center and 1/4" higher at top dead center .... so to use the same rods .... the 400 pistons have their wrist pins 1/4" higher on the piston than a 351M piston so the piston isn't shoved 1/4" into the head.
My 351M in my truck has a smaller HB than the '79 400 I have on a stand but the counter weight is near same as far as I can tell. 351M and 400 can use same flywheels, but trucks with 400 and manual got a bigger clutch generally than those with 351Ms.
351M is OK .... and the reason some say it's weak is .... I think ..... because Ford never offered it OEM in a performance application. It is a "tall deck Cleveland". The first Cleveland was the 351C, then they made a 400 to use same head style but a tall block, then they later made a 351M from the 400 by tossing in a shorter stroke ....

 

Hey gator... Yep I realize that it's a old post I'm new here and thought I might scan over all of the old posts history just to see if there is anything the that I need before I post a new message for it... I'm sure all the old info is as relevant today as it was back in 1999... There is a lot of good stuff here and I am very grateful to everyone who has shared and helped... There is much to learn from all of these posts... Thank you for contributing!
Django.

 

LOL .... I missed it ..........

Oh well ..........

 

351M 101: M-Block 351M/400 Parts Reference

Rumors & Myths

http://grantorinosport.org/BubbaF250/index.html

 

In my limited experience I've had two 351m engines with a broken cam shaft. Maybe due to the oiling issue discussed in earlier posts? Both were already in vehicles I had bought. I just got another '79 with a 400m. Maybe I've been unlucky, but I will be replacing it with a 460 in the near future. Just my two cents.

 

Yeah it's an old post. Now it's 2022 and this thread still has some of the most incorrect information available. First, the 351M is not a weak engine. It is in fact, a MODIFIED 400. The only two internal differences in the 351M and 400 are pistons and crankshaft. This is because of the 351M's 1/2" shorter stroke.

Secondly. Ford Motor Company never gave the 400 a suffix, such as "M". The M in 351M stands for one thing and one thing only and that's MODIFIED. This is easily verifiable by looking at an original 351M that has not been messed with. The valve cover engine identification stickers ALL said "351 MODIFIED 400" Every single one. The reason for this is simple. The 400 engine was put out first, beginning for the 1971 model year. The first year for the 351M engine was for the 1975 model year. Ford took a 3.5" stroke crank and pistons with a longer compression distance and created the 351M. The M never meant Midland or Michigan, as the engines were also produced in the Cleveland plant. There simply IS no confusion for those with even grammar school comprehension skills. It is printed right on the Ford Motor Company engine identification stickers that were all on the valve covers from get to go. Ford called it MODIFIED. That's what it is. Anything else is made up bull**** internet fiction to try to make someone sound intelligent.

Third, The 351C, 400 and 351M are all in the Cleveland 335 series family. Ford never called it the "M" family. There is only one M engine and the 351 MODIFIED 400 is it. That's it complete name. 351 MODIFED 400. It was a 400 MODIFIED to displace 351 cubic inches with a 3.5" crankshaft. MODIFIED, MODIFIED, MODIFIED.

Lastly, All of the Cleveland 335 series engines are some of the best engines Ford ever produced, IMO. Had the Ford engineers ever thought about the benefits of a quench chamber, the 400 would not have had the reputation for spark knock and detonation that it was plagued with. IMO, Ford kept going the wrong way lowering compression through the years trying to combat detonation. They just never got a handle on it. All they had to do was design a cylinder head like the Australian Cleveland closed chamber 2 barrel head and all of their problems would have been solved. I love the 335 series. Easy to work on, still easy to get parts for and cheap to build. They are real stump pullers, especially when you correct the stupid retarded camshaft timing Ford was so famous for. They will really turn it on.

There's your 2022 update for a resurrected thread.

Thank you drive through.

 

show me a factory valve cover that says 351 modified 400 and I’ll send you a crisp $100. Keep with the misinformation.

 

And you have to post a PICTURE or it did not happen. Unwritten FTE rules.

 

Call them what you like they're still weak.