Originally Posted By: Fester
Originally Posted By: daves66nova
Any chance the seals can be changed out without taking off the head?
No. The valves would drop onto the pistons.
So? One common procedure is to rotate the engine until cylinder number 1 is at TDC, do all the cylinder 1 valves, then rotate to #2, do all the cylinder 2 valves.... etc. With the piston at TDC, the valves can only drop slightly. The piston keeps them from falling all the way into the cylinder... which would be BAD. Its sometimes tricky getting the valve re-seated and the keepers back in place while the valve spring compressor is in the way, but it should be relatively easy on an OHC engine with light valve springs.
An alternative method is to use compressed air to hold the valves shut on one cylinder at a time, but I don't like that method. It puts the piston at BDC, and if the air source should poop out in the middle of the job, the valves could indeed drop into the cylinder.