If your engine has a symmetrical cooling head and you have removed it to service your engine, it’s best to remount the head in its original orientation. This is because microscopic asymmetries in the original positioning of the head can affect the piston “wear-in” during break-in. If you remount the head with it’s front rotated, the alignment and piston “pinch” will not be precisely the same. A good practice is to use an Xacto blade to scratch a small “x” on the front of the head— guaranteeing proper alignment when bolting it back to the crankcase. Also remember to cross-tighten the bolts as if you are tightening down lug nuts on a car wheel. You can tell when the head is perfectly mounted by turning the prop with your hand—it will offer the least resistance when the head is perfectly seated.
Dave Gierke, Lancaster, NY