valve seals??

You can use the rope trick to keep the valves up in place while you replace the seals.
Make note of you firing order.
remove all the spark plugs
use a 3/8 SOFT nylon rope about 6 feet long
feed it into a cyclinder that is half way up on the compression stroke (both valves closed). DO NOT USE THE STARTER rotate the engine by hand. You will feel the rope compress against the valves and hold the vales up. (I lock the engine in place using a pair of vice grips on a pulley to insure that the engine doesnt move) Replace both of your seals for that cyc. Remove the vice grips and back the engine up. Pull the rope out and go to the next cyc.
Frank