I've got an '85 with a 305 ci. The valve guides leak a little on cranking, and there are a few drops coming from the rear main. Should I start using 10w40 sans 30 weight? I live in Tennessee so climate isn't generally an issue. I just thought it might help these leaks a little till I put my bowtie 500ci, all aluminum Nitro Methane monster motor in it. I mean my pep boys 350. "who dares wins"