Do you mean unshrouding the valve in the chamber? Its best to unshroud the intake more than the exhaust side. See the intake charge has the hardest time clearing the valve to enter the cylinder than the exhaust charge does leaving the cylinder. The reason being is because the intake charge has to be drawn into the cylinder under vacuum whereas the exhaust is just being forced out of the cylinder by the piston with positive pressure. Watch this video on freshening up heads from Power Block TV.
