Change Valve Seals on Engine

I need to change the valve seals on my CJs V6. I am doing this without removing the head. I have an adapter for the spark plug hole for compressed air. If I use compressed air to hold the valves in place before removing the keeper, what kind of air pressure do I need to maintain in order to keep the valves seated on the head while changing the seal and replacing the keeper? The piston will be at TDC or near. What have others done? Any hints in doing this job this way?

Thanks for the help!

 

Are you sure you have them? These motors did not come with them from the factory, in fact most engines of this vintage did not have them.

 

The last time I changed some valve seals. I did it with nylon rope. I fed some rope through the spark plug hole of a cylinder and then turned the crank to hold closed the valve. This way I could compress the valve spring and remove the valve spring keeper. I think I made some tool to press the spring down to remove the keeper. It's been a while. IIRC

 

I used about 65psi on mine. My 225 didn't have seals so I used the ones for a 231 and they fit perfect. They had 2 outer springs. I took the top one off for easier installation and used a deepwell socket to push them down they I re-installed the top spring.

 

I tried the shop air trick, found that I had to be EXACTLY on TDC or the piston would suddenly drop to BDC. So for the rest I used the cord which I consider much safer. Not easy, just safer. ymmv.
Mike

 

I just rotated the cylinder to TDC. That was enough to prevent the valve from falling thru.

http://www.earlycj5.com/forums/showthread.php?t=29062

 

You can do this from BDC. Simply remove the rockers, add air, then remove the springs.