Valve Job

[sleepydsm]

My DSM has 142K on it. I have poor compression in #1 and #2. I am pretty sure it is the head that is loosing the compression. What happens to the head over time that causes the cylinder to lose compression? I assume it has to deal with how the valves are seated when they are closed? "Air" leaks past the valves? I'm guessing I need a "valve job." What exactly would a machine shop do to my head? How much does this cost? I'm sorry for the barrage of questions, but I have a head sitting in my garage that wants to be reattached to its lower buddy. Thanks all!
-Kevin

[Jakey]

N/M