That is getting to close for comfort. It is not the valve's that are the problem. It is the piston hitting the head itself at higher rpm's. As the engine gets more wear on it the closer the pistons will get and then there is the rod stretch. I know I wouldn't trust one that tight. Monte is telling you the straight scoop.
is that why sometimes a well worn engine seems to run so strong?From what you are saying,it sounds like it would boost compression,if even a little bit,because the piston is moving higher in the bore?