The manifold needed replaced when I bought the tractor. It just didn't seem right but I finally got around to looking for the casting numbers. No numbers. Just Heisler MFG CO on the top left hand side of the intake. The firing order is as it is on an Oliver manifold. That explains the absence of the &quot;butterfly&quot; for distillate.
I have traced Heisler MFG to Waterloo, IA or St. Marys, IN.
Any clue??