Replacing valve guide seals:
Replacing valve guide seals without removing the head can be accomplished without fear of dropping the valve into the cylinder.
1) Remove the rocker covers.
2) Remove the spark plugs. (Be sure to mark your wires)
3) Bring the cylinder that will be worked on to the beginning of the compression stroke.
4) Take about two feet of 3/16ths vacuum hose and fill the cylinder, through the spark plug hole. (Leave a length sticking out so you can remove the hose when done).
5) Turn the crankshaft by HAND until it bottoms out and compresses the hose.
6) Remove the rocker arm of one valve at a time for the cylinder.
7) Compress the valve springs: remove the keepers and springs. (With appropriate tool)
8) Remove and replace the seal. (Pre lube the new seal)
9) Install the valve springs and keepers.
10) Replace rocker arm. (Adjust to specs)
11) Turn the crankshaft and remove the hose.
12) Reinstall the rocker cover, plugs, and wires
13) No more black smoke :o)