How hard is it to replace the valve seals on my 305 Z-28 with the engine in the car? How do you go about it? And do i need any machine work or special tools?

Thanks, i would like to fix the smoke at startup issue.

 

Not to hard but time consuming.

First remove the vavle covers and spark plugs. You'll need a air compressor feeding about 6 psi through the lines. You can buy a part the hooks up to an air line and screws into spark plug hole. This will keep the valves up inside the head. If you don't have this then I'm not sure how else to keep them from falling on top of the piston. Maybe someone has another suggestion. Anyway, Take the rockers off, the keepers and retainers, remove the spring (You'll need a valve spring compressor for all of this). Then use a valve seal remover and replace the valve seals. This is the basics. Then of course install everything back on.