Necessity is the mother of invention

[Ian Williams]

A burnt seat caused by failure to remove past pitting will cause far more damage, I have had to deal with a few AUSTIN 7 engines in recent years with this malady. My belief, rightly or wrongly, is that with little used cars ( and all of these were little used or recently recommissioned without the benefit of a valve grind I should add ) the valves sit open for extended periods, rust forms on the exposed seats, when the engine is run this rust effects the valve sealing properly and burnt seats result. Now Auckland has at certain times of the year quite high relative humidity, so it may not be such an issue in other places, but certainly something worth thinking about. The engines I am discussing in every case had not completed a high mileage since the last valve grind, certainly far less than one would normally consider necessary. I should also add that the cars effected, when used, were only taken out on relatively short runs and I believe this is another factor, how many times have you gone on an long run 150 miles or more with some decent constant speed sections to find the car is running better than ever. My thoughts are that a decent hammering of the seats, provided they are not too bad to start with settles them back in as well as possibly removing some build up.