I jus got a 3 angle valve job and need to know if i need to get my bottom block resurfaced. The guy at the machine shop said to just block sand it with 100 grit. ??? that doesn't make sense to me cause won't i be scratching it up and where are the extra shavings going to go when sanding.. So i need to know whether to resurface or leave it alone and if it is possible for me to do it.