Re: valve stem seals

Posted by Owen_Dyneto On 2010/3/23 12:59:07

The short answer is that since intake valves are open as the piston moves down and creates suction, oil can be pulled past the guides/stems if there is too much clearance. But the exhaust valves are only open when there is the positive pressure of the piston pushing the exhaust products from the cylinder, hence the opportunity for oil to get drawn in is nil.