Replace valve seals on a 1988 mitsubishi mighty

The safest way is to remove the head and work on a bench. With the use of a special tool you can change the valve seals with the heads on (worst case scenario you drop a valve and have to remove the head to retrieve it). When you remove the overhead cam or the rockers all the valves will be closed. If you remove the spark plug and screw in an air nozzle hooked up to an air compressor you can remove the valve springs, with a valve spring compressor, and replace the stem seals. It will take about 100 psi and you will want to replace the seals one at a time. You should be able to buy the air compressor fitting for the spark plug hole from Mac or Snap-on. I made one from an old spark plug by knocking out the porcelain and attaching a hose and air line fitting (risky, but it worked on my Goldwing)

Mcdevito75 here, That is a shop only job, the entire cylinder head has to come off and either a rebuilt installed or your old head is taken to the rebuilder, Most heads are made of Allumimum and extra care has to be taken removeing them from the engine, also you"d need a special tool to reove the valves from the head and another special tool to remove and replace the valve seals. Have the shop do this job.