21 stud - 24 stud
 

What year did Henry begin the 24 stud head pattern?
Thank you.

Re: 21 stud - 24 stud
 

During 1938. I think they were retooling to allow for the upcoming 239 engines...if you look at the point of change right below each cylinder, you will see how close the stud there was to the bore at 221 size and how they solved that by putting 2 studs over a bit under each hole.