Q: Can I replace valve stem seals without removing the head?

Replacing valve stem seals without removing the heads will typically require a couple of specialty tools to accomplish. On a given cylinder, you will want to be sure that both of the valves are closed. Then you remove the spark plug and fill the cylinder with air through the spark plug hole. This is where the first specialty tool comes into play. An adapter is threaded into the spark plug hole and then connected to an air supply. As long as the valves seal adequately, the air pressure in the cylinder will hold the valves in place while you remove the valve spring keepers, and the valve spring seals. This is a fairly advanced repair and I would suggest getting the assistance of a professional if you have any doubts. If this is something you want to have done, contact a certified mechanic, like the mobile mechanics available at YourMechanic.com.