No valve adjustment?

If it's the later hydrolic engine, there is no adjustment to make. If you have valve noise, you have something worn out (not surprising with todays' low/no-zinc oils). Most likely cam and lifter but I'd pull the rocker assembly and push rod on the odd chance it's something easy and cheap. The later heads don't use spark plugs with gaskets. They use a tapered seat plug with a 5/8" socket size.