Hi, this is my first post.

I acquired a 351 M 400 recently because the price was right. Now, I get to looking at it, and wonder what it is for. The emissions sticker on the valve cover says its for a 78 model vehicle. Are they truck engines, car engines, etc??? Are they good engines? Any weak/strong points I should know about it??

I just wanted to know some history, or any real bad points, I should know about it. Sorry if none of this makes sense. Thanks.

 

The 351M is destroked 400, Ford started using these engines in the 1977 model year replacing the old 390/360 FE engines. I had a 400 in my old '77 F150 XLT. It had well over 200,000 miles on this Truck & had no problems with it.(except for the fact it was a gas hog!) BTW---the 400 did start out as a car engine.

 

Thanks for the reply Tailgator. It's good to hear some information about it. Can they make much horsepower?

 

I used to have a 73 LTD with a 400m. The 351M 400 engines are basically a 351 Cleveland with a taller deck height. They also changed the bellhousing pattern to match the 385 series engines (429/460). With some compression they run fairly well. The design is good but they are somewhat restricted in the exhaust ports as most Fords of that era were. However with an aftermarket intake and a 4 bbl they run fairly well. Only problem is they never caught on with the aftermarket and good intakes were either hard to find or expensive. Sorry to be long winded but the same techniques that made the 351 Cleveland run so well
will work nearly as well on your engine. Finding the correct parts is the only problem. Good luck

 

IMO the 351 M 400, just a 351 with 400 heads and crank I thought are a great engine. I have driven lots of them and know several peopel who still do. One friend in paticular has 78 f250 with a 351M that is super stout. I once drove it and accidently left the parking brake on and didn't even know it. I did by the time I got home. He used the truck as a mud bogger at local bi-weekly mud run they have. He consistantly got 1st - 3rd places running agaist Chevy small blocks, Chevy big blocks, other Fords and some Dodges. His times were like about 7 seconds threw about a 200 foot pit (pond). Unfortuantly the ause did take it's toll this winter. While driving on the street he had mutiple piston rings go out causing a loss of about 3 quarts in 5 miles.
He did rebuild it and it's better than ever. Block was unhurt no rebore need. He did swap in a high profile cam, man does that thing lope now. Had to get a vacuum canister just to keep the power brakes. This year the pit is much longer and right now has too much water. After his second time he has decided with the rebuild it's not worth ruining the truck or motor again.

 

THIS IS JUST A SMOG MOTOR FROM THE MID 70'S. DONT WASTE ANY MONEY ON IT, GET A 351W OR 302 .THERE IS MORE PARTS FOR A 302 THAN YOU CAN BUY. ALOT CHEAPER AND MORE HP.

 

The 351M and the 400M are great truck engines, the 400 being better because of the .50" longer stroke. At a miminum, put a 4 barrel and a good dual plane intake and RV cam which will wake them up big time. Also, look into early 70's Cleveland pistons for more compression. You're probably looking at 250 to 300hp and 350 to 425 torque. I've got a 400 in my 78 Bronco and makes alot of power, could not be happier.

Sorry, K Jones, but a an equally built 400 will run circles around a 351W or 302.

 

Thanks for the replys. I'd like to find a late 70's Bronco to put it in. It will be a while though.

Is there anything that can be done in the heads to open up the exhaust ports?

A Chevy guy told me one time about the bottom of the rods hitting the block, or something to that effect. Is there any truth to that??

 

Just to add my $.02......

We had a '78 F-250 with the 351M. It was a gas hog. But that was the only minus. It had enough torque to pull down trees, and it was still going strong @250,000+ miles. All the maintainence it required was oil changes and a new water pump.
It is based on the 351C, arguably one of the best blocks Ford ever made, and will, if properly tuned run a 351W into the ground. However, as was stated previosly, parts are hard to find.

Second hand info:
Guy at work has a 351M in his CJ-5, says it gets about 10 mpg, but will "climb walls".

They don't make THAT much HP, but are torque monsters. Couple it with a good Borg-Warner and a good trans case, and it's a great off-road engine.

Magnum

 

the aftermarket heads available for the windsor alone make it a better choice. the current heads are well, 25 years ahead of the cleveland. for the weight of the 400 modified I would go with a 460 as there are aftermaket heads available for it also.
or a 351 with alum heads that would make great power and be lighter than the modified.
one only need look at the 5.0 race seen to see the outragous power people are making out of a windsor. the only advantage i see that a 400 has over a 351 is the cubic inches.

 

A 351M (MODIFIED) IS NOT A 351C OR OR 351W OR 400WINDSOR, AND IT WILL NOT RUN CIRCULES AROUND A 351W. THIS IS A SMOG MOTOR WITH SH_T HEADS. DON'T BULL SH_T THIS GUY, USES IT TILL IT BLOWS AND GET RID OF IT.

 

Hhmmmmmm, I take it that you don't like the engine K Jones??

 

I am building a 400m and it has new L427p dished pistons in it. The comp ratio figures to be only about 7.7:1 with a 79cc head. The piston in the block measures -.36cc because of the fairly deep dish. Anybody know who makes a flatop piston that could be used that would get the CR up to a more respectable level. Maybe 8.5:1 or even up to almost 9.9:1 or so. I can't find anything with the proper pin bore and the tall rod length of the 400m. Any suggestions except get a 302 or 351W.

 

Wow, some people are a bit touchy, but in all honesty, K JONES is right. If the truck is original, then I'd leave the original engine, but if you don't care about that, you can spend probably less money on a 351w or even a true 400 and you can get tons more power out of either one of them than a 351m. They're fairly durable, I drove one for about 400 miles with no oil and it had never had any additives in the engine or anything...When we pulled the engine about 2 months later, it would still crank and run, didn't feel like it lost too much power, either...

 

It's been a while since I've seen Hot Rod, Popular Hotrodding articles but there are articles out there that tout 20mpg with the 351M in a truck with std. transmission. Heads can be ported to open them up, but like others have said, not much interest was generated with the engine and you may have difficulty finding parts you want. Some of the misconception is that it is not the 302 Boss (although there may be some parts swapping opportunities since the heads are similar), the 302, or the 351W; I'm not sure about the relationship to the 400.

The M stands for Modified Cleveland. To recover some of the performance with the M, you can get a late '60s 351C cam sprocket to restore what Ford did to the cam timing to comply with emissions.

I had the M in a '79 Tbird; 10 mpg around town - 21 on the highway (no air cond, Maine care) but jeeez, what a ride!

Best of luck with the torque monster!