how to tighten thread on the valve lash adjustment screw

Curious to hear if something can be done to the threads to make them tight again.[/QUOTE]

You can tape the access hole for a #8 set screw. Adjust the valve then tighten the set screw against the adjuster screw. It would be better to do like Rusty said and run a tap thru and get the lock nut and adjuster set.