How important are the o-rings in the valves?

I simply can't install them so I might have to leave them out and only use positive seal + umbrella type seal. Just got a $60 comp cams valve spring compressor but even with that I can't compress the springs tight enough to even see the second groove where the o-ring should go.

I've tried installing the o-ring before compressing the spring but this just doesn't work, the o-ring gets gouged out.
I also tried poking the o-ring in with a small screwdriver but this is so inaccurate that you can never know if it's actually in place or not.

 

If using a positive lock or umbrella seal then the stem o-rings are not really required. Generally they get dried out and brittle anyway from the hot oil.

 

i had to replace my umbrella seats in september its not too hard if u have compressed air or even a few zip ties that are one peice, compressed air is easier to use to hold the valve up from falling n the cylinder. i made a spring compressor out of flat stock i had, but like AlkyIROC said you dont need the o-rings. but if you want to use air hold the valve up and work with it that way you can find step by steps online or go to the part store and buy a haynes book for our f bodies. if you decide to pass the umbrella seals the o rings will still go bad quicker and you will shoot blue smoke out the tail on start up.