I just recently had my headgaskets replaced after I discovered an internal leak. While the engine was out and the heads were off I decided to have the the valve clearances checked and have a 3 angle valve job done. My engine has 107,000 miles on it by the way.
During the process of having the headwork done - The shop discovered that my exhaust valves were out of spec- in this case, those valves had begun seating more towards the bottom edge of the valve instead of the top edge of the valve. As he explained it "When valves wear,(mainly because of mileage) the valve seat deteriorates as the valve presses into the head and will start to seal at the bottom edge of the valve instead of towards the top edge. As more of the area of the valve becomes exposed to exhaust gas, the problem quickly worsens and the valve begins to not seat at all. As a result, the valves can eventually burn/deteriorate because exhaust gases are leaking around the valve, never allowing it to cool." Thought I would share the info.
Last edited by KCwagon; 03-05-2011 at 12:20 PM..