I realize this is just stating the obvious........ but........ there are thousands of these heads in service....... for well over a decade...... where the owners are enjoying leak free operation.

As opposed to something like a MP 518-M MW head...... where I’ve seen the valve cover rail vary by over .125” in height from one end of the head to about the mid-way point....... then back down again to the other end.

Have fun trying to get that to seal.