If none of the plugs are shiny black you don't have oil on them dull black = dry, shiny black = oil on them, been there, done that, especially on Hemiroid motors with no spark plug tube seals I do retighten the intake manifold bolts many times over( I wait twenty to 30 minutes between each time) and over until they don't take any more movement with a good inch lb. torque wrench, same thing after running the motor to warm it up, retighten those bolts many times until they stop tightening