351 M and 400 engine

farmer ford · #1 (**permalink**) 05-16-2008, 07:28 PM

What is the difference between a 351 M engine block and a 400 engine block?
Are they the same just the 400 has bigger pistons and crank? Thanks

mark a. · #2 (**permalink**) 05-16-2008, 08:05 PM

The blocks are the same. They both have 4" bores stock. The difference is the crank and pistons, the rods are the same.

farmer ford · #3 (**permalink**) 05-16-2008, 10:12 PM

can a 351 be a 400 with little cost and effort?

fastfarmer · #4 (**permalink**) 05-16-2008, 10:22 PM

Yes, just install 400 crank and pistons and you've got a 400.

jokerforever · #5 (**permalink**) 05-17-2008, 02:10 AM

FYI, this is a great swap but if you do it get a set of flattop pistons. The 351M and 400 are good motors but the low compression (and weak, retarded cams) is what gave them a bad name. The best thing about this swap is that flat top and forged slugs are available for the 400 to fix that problem and make the most of those wonderful Cleveland heads. That’s not the case with the 351M as you’re stuck with replacement pistons only. I picked up a 78 last year with a 351M and had plans for a 460 swap. But the more I drove the truck and the more research I did I have now changed my plans for a 400 (or possibly a 434 stroker) upgrade instead. Join them down in the 335 Series Forum and they can help you put together something special.