351m swap

[fmfgnarly]

Hi,
I just picked up a 1990 mustang with the 4cyl. I was thinking about droping in a 351m 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

[GTStang]

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

[Rod&Custom]

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

[fmfgnarly]

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

[SVTcobra306]

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.

[fmfgnarly]

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.

[SVTcobra306]

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...

[GTStang]

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.

[fmfgnarly]

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?

[GTStang]

What year is your Mustang?

[HiFlow5 0]

Originally Posted by GTStang

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.

[fmfgnarly]

Read??? LoL...Its a 1990

[GTStang]

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.

[fmfgnarly]

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?

[duplox]

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.