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 The
351M/400, or 335 Series engines are, in my opinion,
one of the most
overlooked and under-rated Ford engines ever made. Just
talk to any Ford enthusiast about these engines and chances are they will
not have anything kind to say about it. However, having owned a '79 Bronco
with one of these engines for 14 years, I believe they are wrong, dead
wrong about these engines. After all, any engine that can take the kind of
abuse I've put my 351M through and still last almost 200,000 miles can't
be all that bad! I even know of a 1981 F-350 that had a 351M that went well over
400,000 miles without a rebuild. That's right -- FOUR HUNDRED THOUSAND
MILES!!!
So,
as we all know that actions speak louder than words, I decided I was going
to take it upon myself to prove them all wrong! So, I'm writing a series
of articles to demonstrate how to build a 351M/400 that will perform as good
as any other Ford engine out there.
Before
I can describe how to properly build one of these engines, I need to address
the legitimate problems and the myths surrounding these engines that are responsible
for their horrible reputation. Take a look at the two lists I have compiled
below:
Legitimate
Problems
-
All
of these engines were loaded down with primitive, first generation
smog controls throughout out their entire production run.
Ford
never produced a "high performance" version of this
engine. -
All
351M/400's were only available with a 2BRL carburetor.
-
Most
351/400's were fitted with severely retarded timing chains and
camshafts to help
meet stringent pollution control standards.
-
The
351M/400 engines have "thin wall" castings and can not be
safely over-bored beyond .040".
Common
Myths and Folklore (as I like to call it)
-
All
351M/400's have problems with cracked blocks and heads.
-
All
351M/400's have crankshaft oiling problems because Ford enlarged the
main journals from 2.75" on the 351C to 3.0" on the
351M/400 but did not decrease the size of the oil galleries leading
up into the top of the engine to properly balance the oil pressure.
-
It
is impossible to build these engines for high horsepower due to inherent design flaws.
-
They
weigh more than the 429/460.
-
They
make great boat anchors.
Now,
lets tackle each of these items one by one. First, I'll address the legitimate
problems associated with these engines.
-
All
"M" block engines were loaded down with primitive emission
controls -- Many people have put down the "M" block
engines because they are in fact loaded down with emission controls.
But guess what? So was every other 78 & 79 engine, regardless of
who made it! Admittedly, the "M" block had some exhaust
gas recirculation features built in to the intake manifold, but this
was done to eliminate all of the air and exhaust tubes that had to
be added externally to the older 302/351Ws and 429/460 engines.
However, if you are the kind of person that still gets upset just
knowing they are there, then simply replace the factory 2V manifold
with a non-EGR unit. Problem solved.
-
Ford
never produced a "high performance" version of this engine
-- Actually, this is not entirely true. Ford build plenty of
HI-PO 351 Cleveland's, which is very similar to the "M"
block engines. The main difference between the 351C and 351M/400 are
the length of the connecting rods, which are 0.8" longer on the
"M" engines, the main journal size, which is 2.75" on
the 351C and 3.0" on the "M" engines, the block deck
height which is 1.09" taller than the 351C, the intake manifold
which is about 1" wider than the 351C, and the transmission
bolt pattern. The cylinder heads, the distributors, the entire valve
train (except for the push rods), the water pumps, the oil pans, the fuel pumps, and the oil
pumps will interchange between the 351C and the "M"
engines. Therefore, there are plenty of HI-PO parts that were
designed for the 351C that will work on the "M" engines.
Besides, who in the world actually has factory original HI-PO parts
from engines such as the Boss 302 and the 429 SCJ on their 302 or
460 truck engines? Folks, this is what the a-f-t-e-r-m-a-r-k-e-t
parts industry is for!
-
All
351M/400's were only available with a 2BRL carburetor --
Actually, I'm not so sure about this one now. It has been brought to
my attention that Ford did offer a limited number of 351M/400 equipped
Broncos with a 4V carburetor. However, a 4V 351M/400 is very, very
rare so for all practical purposes, just about every 351M/400 ever
made only had a 2V carb. However, upgrading from a 2V to a 4V carb
is easy because Weiand makes a set of spacers that will adapt the
much more common 351C manifolds to the "M" engines and there are plenty of
aftermarket (hmm.... there's that word again) 4V manifold available specifically
for the "M" engines. Problem solved!
-
Most
351/400's were fitted with severely retarded timing chains and
camshafts to help
meet stringent pollution control standards -- Yep. This is true
too. After 1973, Ford started putting the retarded "smog"
camshafts in the 400 and the 351M had the "smog" camshaft
throughout it's entire production run. But come on, who do you know that would actually put a 100% original
Ford timing chain and camshaft back into their engine during a
rebuild? There are many quality aftermarket cam shafts out there by companies
such as Comp Cams, Crane, Wolverine, Isky, and Edelbrock. Again, Problem solved.
-
The
351M/400 engines have "thin wall" castings and can not be
safely over-bored beyond .040" -- Okay. Don't let this
scare you away from "M" block engines. Ford did this to
save weight. An "M" block engine is good for one or two
complete rebuilds before you have to sleeve the block. All this
means is that you can't over bore an "M" engine much
beyond .040". As an example, when I had my engine rebuilt, the
shop found that the #1 piston's wrist pin came loose and scored the
block. A .030" over bore would not clean this cylinder up, so
they had to put a sleeve in it. Big deal. It cost me $75.00 to fix
it.
Now
let's address the Myths and Untruths that some people have been spreading
around about the "M" block engine:
-
All
351M/400's have problems with cracked blocks and heads -- This
nasty rumor got started  because there were water jacket cracking
problems associated with certain "M" block engines that
were cast at Ford's Michigan (Code MCC) foundry prior to March 2nd,
1977. All "M" blocks that were cast at the Cleveland (Code
CF) Foundry
are okay. Your 78 or 79 "M" block should be just fine
unless you have a very early model 78 Bronco made in 1977 or you are
working with an older 351M/400. In this case, you should
check your engine casting code to make sure it is okay. The casting
code on the 351M/400 engine consist of 4 digits. The first digit is
the year in which it was cast. The second digit is the month
(A=January, B=February, C=March, etc....). The last two digits
represent the day of the month the engine was cast. The casting
code is  located on the top rear face of the block right next to the
oil pressure switch (See Fig. 4 below). Fig. 1 shows an "M" block
engine with the casting code of MCC 7C01, which means it was
cast at the Michigan
foundry on March 1st, 1977. Fig. 2 shows the casting
code off of my engine, (MCC 9B28) which shows that it was
cast at the Michigan foundry on February 28th, 1979. the
"9B28" is upside-down because that is actually the way it appears
on my engine. Yours may be right side-up as in Fig. 1 or upside-down
as in Fig. 2. I have seen them both ways. Fig. 3 and Fig. 4 below
shows a 400 with the common 351M/400 water jacket crack. In Fig. 3 you can see
the crack about 1" up from the top of the lifters extending
about 4" to each side of the center.
 |
 |
|
Fig
3. - The dreaded
351M/400
water
jacket
crack. |
Fig
4. - Casting
code
MCC before
March
2nd, 1977 |
Fig.
4 shows this cracked block was cast at the Michigan Casting Center
on May 27th, 1976 (MCC 6E27) just 10 months before the 3/1/77 cut off date. I can not stress enough just
how important it is to check your block for cracks before you
rebuild it. Again, you should not have any problems with cracks if
you have the original 351M/400 in your 78-79 Bronco because there
were no abnormal cracking problems with the heads or
blocks on any of the 351M/400 engines built after 3/1/77. --
Special thanks to Jon Colman of Auburn, WA for supplying the
pictures of the cracked M block in Figure 3 & 4 above.
All
351M/400's have crankshaft oiling problems because Ford enlarged the
main journals from 2.75" on the 351C to 3.0" on the
351M/400 but did not decrease the size of the oil galleries leading
up into the top of the engine to properly balance the oil pressure
-- This myth is one that most everyone, even people who like the
"M" engines, hold as being fact. Some people believe that because
the "M" engines have a larger journal diameter than the Cleveland
engines that Ford "forgot" to restrict the oiling
galleries to make up for it. Well, if this is so then why isn't the
351W rumored to have the same problems due to fact that it has the
same journal diameter as the "M" engines?, Also,
installing a 400 crank shaft in a 351W has become a popular
"stroker kit" for this engine, yet no one is complaining
about 400 CID Windsor engines throwing crank shafts! And what about
all of the "M" engines out there with 200 or even 300K
miles on them without a rebuild? Despite all this, some people still
insist that there are abnormal oiling problems with this engine.
There is
even an "oiling restrictor kit" available from Moroso to supposedly
"fix" this "problem". This kit is designed for
high-volume oil pumps in racing applications only. From my
experience the only time an "M"
block may experience oiling problems on the crankshaft is if someone
installed a full-competition high-volume oil pump in an engine
driven on the street. I used a standard volume Melling oil pump on
my engine and it has fantastic oil pressure! The only thing I can
think of that may have "fueled the fire" on the
"M" oiling problem rumor is the fact that this engine was
installed mostly in full-size 4x4 trucks and even saw duty in many
1-ton F-350s. Many of these trucks were used to tow enormous amounts
of weight back in the days before overdrive transmissions. The
"M" engines were also some of the first small block
engines that were now being asked to do the job previously reserved
only for super heavy-duty big block engines. It is quite possible
that some "M" motors may have worn out sooner than some of
the older HD big block truck engines. However, I believe that the
"M" engines are the only small blocks made by anyone that
can even attempt to take this kind of abuse. I think the
"M" engines simply got a bad rap because they were being
used in applications where no small block engine should have been in
the first place. In short, if you need to tow a 10,000+ pound
trailer on a daily basis, then get a diesel or a HD rated gas
engine. But if you use the "M" small blocks they way they
were intended to be used (i.e. in a half-ton Bronco) and you don't
exceed your Bronco's rated towing capacity, then you should get
many, many miles of trouble-free service out of it.
-
It
is impossible to build these engines for high horsepower due to inherent design
flaws -- The only possible basis I can think of that may have
got this rumor started is the fact that "M" blocks have
longer connecting rods for greater torque than the 351C. It is true
that the 351C will rev a little quicker than an "M"
engine, but the "M" engine will develop more torque, and
this is exactly what you need in a heavy vehicle that is driven on
the street. In other words, if you are building a 2,300 Lb Mustang,
then use a 351C, if you are building a 5,500 Lb Bronco, then use the
"M" engine. But just to set the record straight, there are
no "design flaws" in the "M" engines that would
hinder a performance build up.
They
weigh more than the 429/460. -- Someone must have been on drugs
when they started this rumor. This is absolutely not true. The
"M" engines weigh less, a lot less, than the 429/460.
According to Hot Rod Magazine's Ford High Performance publication
(1985), The Ford 429/460 weighs in at 720 lbs and the 351M/400
weighs in at 575 lbs. That's a 145 lbs. difference!
So
as you can see, there is really nothing wrong with the "M" block
engines. As far as small blocks go, it's one of the best engines around. It's bad reputation in Ford circles is totally unfounded.
However, just to be fair to those of you who still hate this engine I must
say that if you are building an 800+ HP super-charged, nitrous oxide
injected drag racing engine or plan on towing over 7,500 lbs. on a daily
basis, then you are better off building a 460. g
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