Since interest was expressed....
I had an old timer show me this one , glue the gaset to the valve cover with weather strip adhesive , it will not move or leak at all , tried and proven
I was taught the same 40+ yrs ago, and never had a problem as long as the surfaces are clean before applying weatherstrip adhesive..
on flat rate, the repair has to work the first time, come-backs are more costly in ways you wouldn't think,, and no-one likes a deduct from their paycheck, because of having to do the job a second time..
Besides, flat rate to change a valvecover is .5, or .7 hr,, from the time you get the job work-order, you don't have time to use matchsticks,, clean it, glue it and screw it..
3M black weatherstrip adhesive,, sticks like crazy, no crankcase vapor issues,, and I've actually found RTV the main cause of gasket "creep",,
This technique usually allows multiple use of a good quality gskts..
