I always seal my engines, as long as you seal the outside and make sure nothing gets in side the engine it will never hurt anything and it can only help. But first I take em apart and clean em out good with Fuel and then slather all the parts with light sewing machine oil for lubrication during break in..My Nova +4 had some metal shavings inside and the bottom of the button had metal flashing that was left from the tapping process. Most engines come clean but why take the chance, 1 small sliver of metal getting caught between your P/S and its rebuild time