[rotorwrench]

Ford outsourced the casting of engine blocks after full model A production ceased in 1931. It was less expensive for them to do that than to keep casting them at the Rouge for low production numbers needed. These contracted blocks have the little Diamond casting mark just to the rear and above the timing cover. They generally all have a date code cast in as well. Ford assembled Model T and Model A engines up to just before the involvement in WWII. Folks still debate what company may have cast these diamond blocks since there were several foundries that used a diamond in their casting marks back in the day. They are good blocks and are found on old agricultural, generator, water pump, and other industrial applications as well as replacement engines.