does anybody know how to tell the diff between a 400m and 351m in a 79 bronco 4 speed?? did ford put the 400m and 4 speeds t-18 in 79 bronco's? thanks.

 

im not sure ive heard of a 400m but id say its a 351m. the 351m is a destroked 400. 400 is 4" stroke and 351m is 3.5" stroke. It should say on the valve cover sticker(if its there) also on the sticker with the emission info as well. As far as telling the two apart just by looking. nothing that i know of to really seperate the two. you could pull a plug out and stick a small rod in and measure the stroke while turning the motor over by hand.

 

is there a big diff between the 2 as far as power, hp, trq, etc? thanks.

 

Ford did make a 400m, I thought it was more popular than the 351m. Have 1 in my 79 F150, and another on a stand to rebuild. Vary popular motor's.

 

so whats the difference between a 400 and a 400m? just for knowledge sake.

 

what do u think of the 351m, 400m motors??

 

i had a 351m in a drop top 71 ltd and thought it was a great motor in that. never had any experience with one in a truck though.

 

of the three 351's ford made my fav. would have to be the 351C that was a great motor.

 

what kind of power does the 351m and 400m make?? are they good motors?? is there lots of performance products out there for mods to the 351m, 400m?? or is it not even worth the investment?? thanks.

 

If it is the original motor run the vin numbers. ford did not put the m behind the 400 only the 351m had the m I think because it was modified from the 400 but like you I call all of them m's if you really want performance 460 is simple swap. I have a good 400 the 351 in my bronco is very tired so it is parked untill I get off my but and install a 460 that I have or what I would really like is a 4bt cummins.

 

ford made 3 different 351. the 351 cleveland, 351 windsor and 351m.

Windsor is a 90degree v8, the cleveland and the M were part of the 335 series. the 351c was the motor used in the mid engine panteras ford built in the 70s. I believe the windsor was used in a few mustangs in the 70s.

these motors were used in lots of applications in different forms and there should be no shortage of parts. There are definately difference between the different 351s.

the clevelands and windors had the same bore spacing and i believe the boss 302 of the 60s was a windsor block with modified cleveland heads.


The power of the motor will most likely depend on its current state, original production date and vehicle. For example the big block 460s made great power but during the height of emissions in the mid 70s were pretty sad. A simple swap of some timing components would nearly double the power and torque. i think pre72 the 460 was rated at close to 400hp. after 72 it was around 200hp maybe 250hp.

emissions was the reason the 400 was not utilized. the 400 was a 351c with an inch taller deck height.


Doing away with poor timing for emissions reasons should wake any of the motors up from the 70s. i dont have actual production hp numbers but with the right carb, exhaust and timing id say 350hp should be easily attainable, but those who have messed with those engines should have some better figures for you.

 

Drop the oil pan, and on the first crankshaft throw, look for a 5M, or 5MA, or 5MAB...that would indicate a 400 (no M), anything else is just a 351M. To gain power, an aftermarket timing set, Comp DEH255 cam, will be a good start. Take it one further, and add an edelbrock Perofrmer intake, 4bbl carb, Aussie heads, etc... The vin will have an S for 400, H for 351M.