I have a 78 F250 with a 351M. Someone wants to pull the engine out and use it in his boat, but it'll only fit if it's a small block. Does anyone know if 351M's are small block or big block? Thanks.

 

Bill Beyer, moderator of the 335 series forum (351C, 351M/400) posted the following in the 335 series engine forum guidelines:

"Avoid speculation on whether the 351M/400 is a "big block" or "small block". These are generic terms which generally apply to Ch*vy motors not our beloved blue oval mills so they really have no place in this group. The 351M/400 has elements relating to both the 385 series and the Windsor series and attempting to categorize them is futile, especially when using monikers which FoMoCo never adopted."

FWIW, the bellhousing bolt pattern on the 351M is the same as the 429/460.

 

Well said Jason...

His boat must need a 289, 302, 351w or 351c.

Marty

 

So, it sounds like the 351M is on the bigger side, and if he's looking for a smaller V8 this one is probably too big? I suppose I could just get in there and actually measure the max height & width.

 

but isnt a clevleand a "big block"

 

I'm assuming that with a boat, the main issue is the bellhousing bolt pattern. The drive system must've been made for a peticular motor. The 'small block' Ford pattern is the same for 289, 302, 351w and 351c - they all have the same bellhousing bolt pattern.

Marty

 

I don't think the bolt pattern is the issue. I think his concern was with the actual dimensions of the engine, that it would be too tall & wide.

 

I am by no means an expert but don't you think the 351M would make a really lousy boat motor anyway?

 

I would suggest a nice 302. Folks who swap V8's into old Scouts and such will tell you the little Ford is trimmer, an easier fit than the smallblock Chevy.

 

This is an ENGINE Question not 73-79 truc k question

 

yep. sorry. i have a hard time not thinking of all my questions as 73-79 questions. i'll try to remember that next time.

 

Some engine dimensions: 221thru302: 24"w,29"Ln, 27.5"ht, 460 wt;
351w: 25"w, 29"Ln, 28.5"ht, 525 wt;
351C: 25.5"w,29"Ln, 29"ht, 550 wt;
351M-400: 26"wi, 29"Ln, 29"ht, 575 wt;
332-428: 27"w, 32"Ln, 29"ht, 625 wt.

 

Forgot the other "big block", 429-460: 27"w, 34"Ln, 29"ht, 720 wt

 

thanks Rancheroracer ! that's exactly what i needed.

 

You can edit your own posts for up to an hour after you make them if you "forget" something...