Originally Posted by sunbelt57
Its in a '77 F150 fwd. The guy who sold it to me told me it was a 400. If no one can tell right off the bat, then what?
Take the head off and measure the bore and stroke?
I thought I saw something that looked like #'s under the starter (passenger side of the block). Maybe I should check the VIN before I waste your time. It may be the original motor.
There is no way to easily visually differentiate a 351M
. They both use the same basic engine parts (block-heads-intakes) so Casting I.D. Nos will be of little help.
The balancers are different, but I have not come across a detailed explanation of the difference(s).
If you are lucky, the VECI Decal will still be readable. Also, there should be stamped on the block a partial VIN of the donor vehicle. This will easily I.D. it. Otherwise, you are going to have to pull a head. The dowel trick is not concise because of the angle of the spark plug port on the 335 SERIES.
Now see how easy that was?
-DIFFERENTIATING THE 335 SERIES ENGINE FAMILY-
-INTERNET MYTHS, LEGENDS AND MISNOMERS-