I tried to change intake and exhaust valve seals on the 2.5 this weekend . tried air first and then rope in the cylinder . i couldnt get the valve to stay up sealed so i could remove the keepers . any advice ? i did get my harland sharp 1.7 lifters installed . noticed all around increase in power range .
you need to "break" the keepers from the dish, i usually put a socket over the dish and give it a tap, but that's with the head off and another socket on the valve to keep it flat, with the head installed it's a bit risky this way.
If that's not your problem then use a slightly bent bar to hold the valve up against the piston thru the plug hole, careful not to damage the threads (that's why you shoud be against the piston - don't tap the dish in this case, i assume you have a valve spring compressor to push the dish down otherwise it's a nightmare (if you don't have get one, they're about $10 or $15 at an auto-parts store).