Does anyone know how to tell 351m and 400 apart just recently bought this 1979 f250 ranger automatic was wondering if anyone could tell what engine it is from this sticker on the driver side valve cover. Thanks in advanced

 

I think all V8 F250's came with the 400. Someone else will confirm

 

F250 2WD could have a 300 I-6 (Standard Equipment); Optional: 351M; 400; 460.

F250 4WD not available with the 460.

To determine if the engine is a 351M or 400, measure the stroke. 351M has a 3.50" stroke; 400 has a 4.00" stroke.

 

The VIN will tell you what it had originally, ND gave you the only way to tell for certain what THIS engine is (without dropping the oil pan).

 

So how do we measure the stroke?

 

M-Block 351M/400 Parts Reference

This is a way using a wooden dowel rod...till I read further down. Says you can't on a 351M.

Another place says...the only other way to tell is, take a spark plug out, and using a small welding rod or piece of close hanger, measure the piston stroke from TDC down to BDC, while turning the engine by hand with a breaker bar and socket on the balancer. closer to 4"- 400, closer to 3.5"- 351

http://grantorinosport.org/BubbaF250/parts/pics03.html

Another way that say yes you can. http://www.fordmuscleforums.com/engi...asurement.html

Great site 351M good stuff. http://www.projectbronco.com/Technic...e_build_up.htm

Forget all that hard stuff. Here's a super easy way to tell if it's a 351m or 400. Open hood (if one is present) look at distributor. Look to the right of distributor at the block. Specifically the timing chain protrusion section where the distributor goes into the iron. There will be a half inch wide rectangular rib extending from the face of the block out toward the water pump. If that rib only goes half way from the block to the water pump -351m- if it goes all the way to the absolute front of the block casting -400-. See the block on the left of this page (one on the right is a 351clevland) that big rib indicates a 400. It'd be half as long if it was a 351m.

http://broncozone.com/topic/20267-351-or-400/ or maybe not.

 

Thanks guys