Anyone know of a tool that can allow me to change the springs like the rocker stud tool used on v8's and such while keeping the head on?
I made a tool using an old spark plug and an air compressor fitting. I drilled out the center of the plug (the ceramic) and found the compressor fitting was close enough that JB Weld held them together fine. Remove the rocker arm assembly, get the piston to the bottom of travel, shoot compressed air into the cylinder and you can use a small (topside) valve spring compressor to remove and replace springs easily. The air pressure will keep the valves up while you're doing this. Just work quickly and don't lose pressure until you're finished...
