I have to bore notch a OEM block and increase the radial clearance for the intake valve in the piston

What would be the acceptable minimum valve to bore clearance (seated and open)? and what would be the minimum valve radial clearance in the piston notch ?

It's a street engine - 4.27 bore - 2.30 intake valve - hyd cam .551/.533 and approx .235@50

The larger intake valve is making everything pretty cozy... I have found varying recommendations in the MP books and some generic recommendations on engine forums - some say the older recommendations were "generous and possibly outdated today"

Bottom line - I wan't to make 100% sure it lives but I don't have enough room to go overboard on the specs either.

Hoping I don't end up with some more expensive mistakes


Thanks