You've got a 446 FE and you've never disassembled a set of cylinder heads???

Oh well, I guess we all started somewhere. Here's how I do it:

Get the big C-clamp looking valve spring compressor. I got mine at Sears. They're not that expensive, just buy one and be done with it.

To use it, there should be some adjustable fingers on one end, and a blunt valve holder that goes on the valve on the other end. The entire thing is adjustable, so adjust it right, it's obvious on how to adjust it. Place the head on the bench, intake side up, with the combustion chambers facing you, so it is flush with the edge of the bench for spring compressor clearance. Open the valve spring compressor all the way. Slide the fingers over the spring retainer, and place the valve holder in the center of the valve, I have better results placing it a hair up from center. Compress it slowly, and the spring retainer should pull away from the valve keeper retainer. It will be stuck to the valve keepers. I use a small piece of wood and a hammer to make the retainer move away from the keepers. You then remove the keepers, and SLOWLY release the spring compressor. Remove the compressor, and remove the spring, retainers, and valve stem seals. You should be able to remove the valve at this time also if you want to. Be sure to keep 'em in order!