I am looking too rebuild my 351m with Clevland heads, i would like too get at least 420 horse out of the motor it is in a 78 f150 4x4 club cab need all the help i can get this will be a hot rod when im done thanks.

 

Not with a 351M it won't. The stroke is too short for adequate torque, the rods are too long, and the pistons too heavy, to get the RPM's for 420 HP out of it. The 351M is a low speed truck motor. If you want to build a hot rod 351 stick with the 351W. You could build a Cleveland but parts are scarce and $$$.

 

I dislike use of the word "impossible"; but Torque's right. 420 horses is a long way (read: tons of money, maybe impossible) from where you're starting. If you're gonna do a full rebuild, you can change your crank and pistions, and start with a 400. You'll spend some money making 400+ horses with a 400, but it is entirely possible. A 400 has plenty of torque when built, so it would be great for your truck. But if you mean hot rod as in racing, there are other engine choices that may be better suited to that application.


Good Luck,
Ernie

 

Are you planning on using 4 bbl Cleveland heads? The heads on your 351M are the same as 2 bbl clevelands.

 

I OWN ONE 1978 4x4 with a soon to be 400 hp+ 351M 400 one main key is
Edelbrock ALUMINUM Heads part#61629 &a head bolt kit.call edelbrock
for thear recommended intake & carburetor it is way cheaper than crate engines. And moor FUN puting it all to gethar and making it work right.
351 M's are thunder thumpers ready to go fast in the mud.