u mean valve cover? if so then it is realy hard and time consuming! if ur still using ur plastic cover then all u would have to polish is the cam gear side of the cover, steps i used when i polished the lettering on my painted valve cover are 180 grit da, 320 grit da, 400 grit wet sand, 600 grit wetsand, 800 grit wet sand, 1000 grit wetsand, 1500 grit wet sand, then 2000 grit wetsand. any aluminum polish will work!