Finally, a burned exhaust valve can increase EGT if it allows some of the ultra-hot gas during peak-temperature phase of the power stroke to leak past the valve and impinge on the EGT sensor probe located a few inches beyond the cylinder's exhaust port. Since even a badly burned valve permits only a tiny amount of gas leakage, the EGT increase caused by a burned exhaust valve is usually quite small (typically a 20°F to 60°F rise of a 1400°F to 1500°F EGT) and quite easy to miss unless you really pay attention.