hi all...I have a question...I just recently got a 78 F-250 4x4 and since I have always been with chevy i'm a little confused...I was told it was a 400ci but the valve cover says 351m. Some people say it is the same difference...others say its 2 totally different engines. I was reading through some older threds and found out that the vin code "s" indicateds a 400...which is the code i have...my grandfather was the original owner of it so I know the engine is factory. Can anyone tell me if it is the same engine or how i can tell them apart.


Thanks, Josh

 

Welcome to FTE. There is no way of telling the difference between the 2 motors on the outside. The difference is the stroke, the 400 having more. Both have a 4.00" bore.

 

There is no way to tell. A 351m is a "destroked" 400 small block that bolts onto the big bolock trannys.

 

Must be a 400. The 351M and 400 are the same except for the stroke. The longer stroke of the 400 helps it produce more torque than the 351. Heads, intakes and all of the externals will interchange.

 

thanks alot guys for the info....I'm really trying to like being a ford guy...

 

My 77 150 has a 351M and the valve cover has both numbers on it. This article was very helpful in understanding the how to and what for about these motors.
http://www.fordtrucks.com/article/id...00_Engine.html

 

thanks pete...that explains alot


Josh

 

It's true the 351M and 400 are the same engine except for the stroke; but won't the vin code tell which one was installed at the factory? I have a '79 supercab that I was told had a 400 in it, it even had a 400 sticker on the valve cover, I checked the vin code and it specified the 351M so I'm assuming it has the 351M, right?

 

mine is a 78 and the vin code for a 400 is a "s" but my engine says 351m...thats why i was confused...maybe someone knows if the codes changed for 79

 

or...maybe i should go back to chevy...my head hurts

 

Okay. Unless the valve covers were changed the 351M and 400 share the same vavle covers. The engine ID sticker on the drivers side one should read "351M/400" and then below it will either be 351 or 400 depending on what it is.

 

i only noticed the one 351m...guess i should look a little closer

 

and while all of you knowledgeable people are here....what the hell is a highboy...and i was told this truck was a 3/4 ton with 1 ton suspenion...is this even possible?...he says he ordered it special that way???

 

A highboy had a factory 4 inch lift, and was a heavier duty truck. It in essence was a 1 ton rebadged as a 3/4 ton.

 

yup...just went and looked at it....says 351m/400 and under it says 6.6l 400ci


now who is the smart one.....dumba** chevy boy..lol