When you say stock valve lash, I assume you mean with a stock car and stock components. Set #1 piston on the firing stroke(both valves closed) tighten each rocker arm to 25 ft lbs. At this point you should be able to spin the pushrod with your fingers....if you can't you need to place a shim under the rocker arm fulcrum to "unlock" the pushrod, making doubly sure the lifter is on the heel of the cam. Then go through the firing order doing each intake and exhaust valve and when you get to #16, you will be a fully qualified valve adjuster.