351m swap

Hi,
I just picked up a 1990 mustang with the 4cyl. I was thinking about droping in a 351m :newburn: that my friend has that i am getting from him in place of my t-bird, and was wondering what all is involved, parts-work...ect Any feed back would be great...Thanx :screwy:

Don't do it, it's not a very good motor for this situation.

I am pretty sure that GT means "don't" do it. You all right GT?

For what reason do you think that this motor is not a good choice? :confused:

The 351M was a late 70's smog motor. Needs better pistons and lower CC heads and a 4 bbl intake to make over 150 HP.

Put on Aussie cleveland heads and a performer RPM or Torker intake wi/ a 4 bbbl and you'll have some serious fun.

forgive the spelling, I'm beyond drunk.

I went on Edelbrock.com and i found a dyno chart that said that with a new intake, carb, headers, and a cam it has about 385 tq at 3500rpms, and about 340 tq at 2500rpms. I dont know about you guys but that dosnt sound to bad to me.

Hope you like spun bearings. The 351M/400 had very large mains but not big enough oil galleys to feed'em.

Now, you could do it right and machine a 400 crank to fit a cleveland block, and make your motor mounts and tranny choices much easier.

BTW that's with new heads, too, You have to run new pistons and heads, M motors had around 8:1 compression.

Otherwise, with the need to go with big-block motor mounts and a big block tranny, why not drop a 429, 460, or >500 cubic incher in there? It wouldn't take up much more space and would make a heck of a lot more than 385 lbs of torque...

First off what are you gonna put this motor in?

Second you'll never make good power on a 351M until you change heads just will not happen.

Third 351M/400 are well know for the spinning of main bearings due to lack of oiling. Reason is they took a 351C block machined it for larger mains and didn't think about the etxra oil needed by the now larger mains. You need to pull a 351M/400 apart and instal an oil restictor kit so that you keep enough oil for the main bearings.


351M/400 can be nice motors but you need to pull em apart rebuild em right and def need a head swap. Also really depends on what your putting it in if it's worth it.

so pritty much what you guys are saying is to not get the "M", I was thinking about droping it into my mustang. Also i was thinking for right now i could just mod the 4cyl thats in it right now. going turbo is a bit spendy for me, im only 18, so i was thinking cam, header-i know i know-full exhaust, intake, ect. plus the gas miles would be a lot better. would this be a good idea?

What year is your Mustang?

What year is your Mustang?
Learn how to read Bobby.

I just picked up a 1990 mustang with the 4cyl.

Just playing man, I'm sure it was an over sight.

Read??? LoL...Its a 1990

Yea I read it above the firt time hence why I posted not good motor for the situation. Then I just brainfarted, any of the 355-series engines are not a good swap for fox-body platforms. If you want 351cu then a 351W will go in easier be lighter and can make comperable hp. If you don't care bout weight and want huge cubes a 429/460 will go into a fox easier than a 355-series and weigh about the same.

ok sounds good, thanx for the info. But like i posted befor, would it be worth it for right now to just mod the 4 untill i could get my hands on a better motor?

yeah there is no point to put a 351M in a mustang, unless you want a big cube smallblock. M's have a taller deck(10.5" if I'm not mistaken) so you can cram a huuuuge stroke in it. They're pretty stout blocks as well. The D7TE truck blocks are the best. You can probably stroke it out to 450+cubes and make gobs of torque. Big mains don't matter if you're not spinning it high. You could definately get 550+hp and 600+tq with a set of cleveland heads on a big inch M-block motor. A guy known as ShaZam made over 800hp n/a from a M block.
M blocks have the same main bearing diameter as 351Ws, 3". Clevelands have 2.75". I've never heard of M blocks having any severe oiling problems, but if they do, oil restrictors will likely fix it.
However, the problems of putting one in is more of a concern. Header fitment especially. That tall block combined with cleveland heads makes for one very big engine. You'd be better off buying a 351w block and putting cleveland heads on it, or just using aftermarket windsor heads. You could just use a Cleveland as well, I know lots of people who put clevelands in Fox bodies, its a pretty popular and easy swap. There are ready-made headers and motor mounts and oil pans for the swap. Its a good drag racing combo.
As for the 4cyl, you could mod it, but I doubt you'd get very much without using a lot of $$. I would rather save the money for a v8 swap.

Clevelands have a very normal oiling system - the same as the 460, same as Pontiac, Oldsmobile, and Cadillac V8s, and same as Chevrolet's 2.8 and 4.3 V6s. A cleveland block will be perfectly happy up until around 6500rpm. With restrictors they'll go to 7500rpm, and with an external oil line/accusump 8500 isn't a problem. You should be running a dry sump system around there anyways, and that'll be good to 10k+. Now, taking into account the bigger mains, 6500rpm on a 2.75" main is about 78ft/sec bearing speed. With a 3" main, that same speed comes in right at 6000rpm. Thats as high as I'd be comfortable swinging the heavy lower end and long stroke anyways. (well, if you have a 351m its the same stroke, but why would you put a 351m in anything unless you're going to stroke it to the hilts?)
I'd say it'd be a cool project if you want to fork over the cash for a custom ground crank. Surely you'd be one of very few to have an M block in a '90 stang. Unless you go to a 460 you'll be hard pressed to beat it for torque...

That is true. My only point is that the amount of work you put into it, you could easily put a 460 in also...

Indeed. I'd only recommend the swap if you want to do the fabrication and have a big wallet and want something different. Other than that, stick with the Windsor, Cleveland, or 429/460.

Ya i dont know how much work exactly would have to go in to it but my dad is a welder, and my friend that i would be getting it from, his step dad builds race cars, so that would help. About how much would it cost to do the full conversion? All the parts and whatnot. One of the main reasons i was considering this motor is because all i would have to do to get it, and the tranny, is trade him my T-bird.

If your tbird is worth more than $200 don't do it. 351m/400 are filling scrapyards to the brim, Ford put them in pretty much everything from big cars to big trucks, there is millions of them.

Just a little side note, would a front bumper cover for an 87-93 GT fit on an 87-93 LX?

Check out the jack roush 427R, its on roushparts.com. i think its a pretty awesome motor, dont know how much ur gonna spend tho

Just a little side note, would a front bumper cover for an 87-93 GT fit on an 87-93 LX?

Yes but you also need the molded pieces that fit on the front /ottom of the fenders to complete the conversion. Otherwise the GT front sticks about 2-3 inches out past the fender on the sides and looks stupid.