Do you have a "tech manual"?
Generally on OHV, Briggs and Stratton recommends about .004 on the intake, I'm saying go to about .003. What that does, is starts the "opening process" just a touch sooner.
Oh, you've checked to make sure there isn't any push rod issues, correct?
Some models use little caps that sit on top of valve stems, did yours have them, and if so, are they still there?
If you don't know, let me know, I'll go into Parts Smart, and check it out for you.
I'm at the shop right now, so make it snappy!