Valve Spring Inspection
Valve springs should be inspected before re-installing them into the cylinder head. In fact all parts and their geometry should be checked before reassembling the valve train. Valve springs like the one in the illustration are made from different metals depending on the engine. They have several designs other than standard springs, some include a damper to reduce valve train vibration while others are variable springs that change the distance in the space between the coils. Dual springs have a smaller spring located inside the larger one. This spring set dampens and reduces vibrations.
A weak or worn valve spring will result in valve float. Valves open and close at incredible speeds and a valve spring must be able to endure these extreme conditions. Valve float can result in damage to other components in the valve train as well.
There are different tests performed on the springs after they have been removed from the cylinder head. The test being performed in the illustration is checking for valve spring squareness. The spring is placed on a flat surface along side a square. Rotate the valve and make sure all the coils contact the square as it is rotated. A feeler gauge is sometimes used and there are different tolerances, as always check the manufacturers manual for any specifications or special procedures. Notice the space between the top coil and the square. The valve stem installed height is the measurement from the tip of the valve stem to the spring seat.
