When does this occur/ I recall from way back when, that the smallest valve to piston clearance is NOT at TDC. So when does it occur? Does the intake valve come closest or does the exhaust valve come closest (given an even cam, like 224/224).What about my 224/230 114 LSA cam? Whats the highest valve lift that I can get away with?

 

intake is the closest at 10 degrees after tdc when it is opening. and exhaust is 10 degrees before tdc as it's closing.

 

You can still have enough clearance with a huge amount of lift compared to a cam with less lift. It all has to do with the valve timing (at what degree the valves are opening and closing). You can have 2 different cams with identical lift and duration but the valves open and close at different times and the cams will perform very differently.

Safe limits are .070" clearance on the intake and .110" on the exhaust.

You can retard or advance the cam to change the valve timing. Advancing a cam increases the clearance on the exhaust and decreases the clearance on the intake. Retarding a cam does the opposite. Many off the shelf cams have a few degrees of advance built into them. Advancing or retarding the cam also moves the power band up or down in the rpm range.

 

The intake valve is "chasing" the piston as it is opening and the piston is "chasing" the exhaust when it is closing. Generally speaking, advancing the cam will pick up lower and midrange HP and torque while retarding it is better for higher rpm ranges.