[UKjohnnycobra]

I have a 1968 vintage 302 with 1966 vintage heads from a 289. I think the valves are out of adjustment. I have followed the "accepted" procedure of; seating the valve; loosening the rocker nut; waiting a couple of minutes; and then tightening the rocker nut unitil I can no longer turn the pushrod by hand (zero lash); and then giving it another half turn. The thing is after a couple I've done this, the pushrod loosens up again (possibly due to the relaxing of the lifter?). Should I retighten the nut a second or even third time, or is zero lash established the first time I tighten it?

All help is gratefully received and thanks.