[dirtball]

I would check it. Longer duration has a lot to do with it too, not just lift. The piston chases the exhaust valve. If the valve is hanging open for a while, the piston will catch it. Not good. I use the checking valve springs like PICKMUP suggested. I just push down on the rocker while rotating the crank over (by hand) until the piston contacts the valve. I continue until the piston pushes the rocker up to max lift. Then I use a dial indicator to verify clearance. Once the dial indicator is set up, I rotate the crank back and then forward to find the minimum clearance.