I don't think they're blind holes. Use some thread sealer if you remove the studs. There are three holes in that area but only two are used on our cars. The back hole is pugged with a cap screw and I forgot to install it one time. Huge oil leak that prompted me to pull the engine thinking something serious had happened. When I saw what it really was, I was determined not to make that simple mistake ever again. So far, I never have.