Q: How to test valve spring pressure and check for squareness using a carpenter's square?
A: Valve spring pressure testing and valve spring squareness can be done by the usage of a carpenter's square. The valve spring is set on a flat clean surface close to a square. Measure its height and then rotate it against the edge of the square to look for any deformation or out-of-roundness. If there is a difference of more than 1/16 in. (1.6mm) between springs, or if one is bent over more than that amount, it must be replaced. Other springs are checked for spring pressures within one pound (0.45 kg) of each other when upside down as well as vice versa, meaning that this test has to be carried out by a machine shop which happens not to be common with most automobile repair shops.