The Ford 351m from my understanding is basically a torque-monster. It was designed to generate large amounts of torque for heavey cars and PU trucks. I also understand that from a HI Performance Racing (Automotive) perspective, the engine is limited to about 5500 RPM. This really doesn't get it up there in the 6500 to 8000 RPM range necessary for drag racing.

What is the limitations within the engine that shuts it down at 5500 RPM? I have some thoughts on this, but would like to confirm with others.

Is this problem related to the weight of the rotating assembly, thereby limiting the speed at which the engine can be turned.

If this is the case would it be possible to chuck the crank up in a lathe, turn the counter balances down by an eighth or a quarter of an inch or so, and then rebalance the crank for a set of light weight pistons and rods. By doing this would decreasing the weight of the rotating mass allow increased RPM.

It seems to me that this engine is built very heavey duty on the bottom end. and anything that has been adapted from a cleveland motor should be able to generate a lot more horsepower. The fact that it has an inch+ more deck heighth should make a canidate for a serious stroker motor.

Just some thoughts.

What do you all think?


Kent Mathew
Dallas, Texas

 

Neither the 351M or the 400 was designed for high rpms but with a lot of work you can make them turn fast. Check out the 800HP smog motor that Shazam has. The 351M is a destroked version of the 400 that was made with a short stroke crank and taller pistons. The rods are the same.

 

I think that the biggest set back is the very poor breathing heads especially on the exhuast side.

 

Compared to what? The 351C-2V heads (which is what 351M/400 heads are) flow as well stock as many aftermarket W heads.

Ford Heads Flow Data

The valve sizes will make SBC owners drool since 2.02 is big for them. The main reason that the 351M/400 is limited in the RPM range is the fact that they only came stock with 2V carbs & intakes. Add a 4V, some headers and a better cam with a straight up timing set and even bone stock heads will push over 6500 easily.

 

So basically what you are saying is if you increase the volume of air in and give it a good flowing exhaust system, (air in - air out) this motor should be able to turn as good as a W motor.

Just for some additional information the casting number on the block that I have is D7TE-A3B My information says that is a 75-78 351M or a 77-82 400 block. It has an additional casting pad with one of these three numbers on it. 707 7D7 or 777. The center number is a little deformed so I am not sure what it is.

I acquired this piece of hi-tech engineering from a barn on a piece of property that a friend just bought. He just wants to get rid of it. I know there is a lot of these motors out there and if I could develope a package of goodies that would make one breathe fire, it would be a good place for some of our young hot rodders to get started.

My latest engine creation has been a 351 W, TFS Street Heat heads. It has a full on Comp Cam roller valve train. The cam is a custom ground Comp Cam unit with 575 intake and 576 exhaust. Victor Jr. Intake, Holly 840 double pumper, Full blown Airmotive Fuel delievery system. Fluidyne Radiator. Complete MSD Ignition system, Taylor wires. The short block was buit by ****z and Company Performance. It is a 351 W, bored and stroked out to a 418 It has JE flat top Pistons and Manley rods. Every nut and bolt in it is ARP.
Compression ratio is about 8.5:1. We have not got it broken in yet, but we are expecting something in excess of 500 HP. Where thinking about a 200 shot of direct port nitrous, with MSD Timing Retard box. We ar looking at tying the nitrous into a computer control unit that will stage the nitrous in and out based on engine RPM+. We will be adding a few other trick sensors to the intake and the exhaust, tying them back into the computer unit to shut things down if there is any problems. With nitrous we are anticipating in excess of 700 HP.
In addition we are running BBK chrome headers and H pipe with Mac mufflers.

We have a performance built T5 tranny and a stock 8.8 rearend. Yea Yea I know they won't last. They are there just for break in. We are eventually going to put in a 31 spline 9 inch with a Tremic T56 or a TKO.

And believe it or not it will all fit under the hood of a 2000 model Mustang. Just barely.

Kent

 

There was a technician from Ford who posted on this forum a while back. He reports that the 351M cam was a pretty good piece. There was also a post that described how to cut down 4bbl valves and fit them into the 2bbl heads with a 30 degree valve job. Very trick and it made huge gains on an already good flowing head.

I don't know if you followed the link that Bill Beyer posted but you might have noticed that the 351 2V heads kicks the @ss of just about every 2 valve cylinder head made. Yeah, I know that peak flow for some heads is higher but if you look at the flow at .200, .300 and .400 you'll see that the stock heads rock.

I'l bet that if you retime the cam for a straight-up timing, and raise the compression a little, the 351M does just fine.

 

ok i will chine in (ya know it was coming)
the 351m isn't a good race engine because of the 1.9++ inch compression height pistons THIS IS A LOT OF ROTATING WEIGHT

if you can conjure up some longer rods than the 6.58 rods in it let us know PLEASE (chebbie parts shall not apply to be in my engine) you may be able to put shorter pistons in it to reduce rotating mass

heads-- the 351m/400 heads ARE simular to the emmision-less 351C but more restrictive

you can get a bit of power out of the stock engine thru the normal routes==
a 600-650 cfm carb MAX
intake
shave the heads a bit and smooth the runners/bowl/chambers/better springs/bigger valves
comp cams 265DEH would be good but still streetable
a good exuast
a (memory fails too much useless info) 72-73 ford elite 351c 4v dizzy modified for full advance

well would have to go over the rest for more info