One of the most common questions is “Do I have a 74 or 80 inch shovelhead cylinder?”
Shovelhead cylinders are basically the same on the outside dimensions. The bore of the cylinders is however different. Standard size 74″ cylinders are 3 7/16″ or, 3.4380″ and 80″ cylinders are 3 1/2″ or, 3.498″ . Visually it can be hard to tell whats is what, and when you get into 74″ cylinders that are like .040″ over size it is definitely confusing unless you have a dial bore gauge or set of calipers. Calipers can be useful but also hard to get and accurate reading because of dirt and centering them correctly.