Torquing something with a resilient gasket like a valve cover won't give good results, brcause the gasket will compress. On something like an oil pan, I like to get the bolts snug, just to the point where there's no more free spin of the bolt, then tighten another 1/4 to 1/2 turn. A 216 valve cover with only two bolts is hard to estimate- - - -too much and the gasket of the cover is damaged, too little and there's a big leak. remember it's always possible to tighten a little more- - - - -once the gasket is over-squeezed nothing much helps.
Jerry