Today I tried to replace the valve stem oil seals on my Camaro 350 tpi. I am using an over head valve type spring compressor, with a wheel at the top and claws that grab the spring at the bottom. I managed to grab and compress the spring on the second coil from the bottom. With the spring compressed as far as it would go, every time I pressed down on the tool to try and remove the keeper/collet, it would move the whole valve assembly down and let air out of the cylinder. Its as if the collect is stuck to the spring on the top? Am I using the wrong tool, it seems like the top of the valve is stuck together? Any suggestions?

IDK what the overhead valve spring compressor looks like.
I would find a place to "rent" the right tool from,or ask some of your buds if they have one you can borrow.
Sorry I'm no help

If you are doing this with the heads still on the engine, you need to hook up a compressed air supply through the spark plug hole & pressurize the cylinder & prevent gravity from "pulling" the valve down. I think some people also shove a string in there instead.

Basically, SOMETHING to hold the valve up, yet easily removeable afterwards.

Give the top of the valve retainer a couple of smacks with a rubber hammer to crack them loose before you compress spring.
You are using this type?
http://www.summitracing.com/parts/OTC-4573/
That type is hard to use at the best of times ; commonly slips off the spring and hard to extract the keepers from inside the compressor.This type works best
http://www.summitracing.com/parts/SUM-906784/

but I find even the budget type easier than what you are using .Can even make it yourself
http://www.summitracing.com/parts/WMR-W84002/

Never had the mallet work for me. I just use a larger socket and put it over the valve stem and whack that with a hammer. I've used the first and the last type compressors that vetteoz linked to, and they both leave alot to be desired, but the first type works well enough once you get used to it.

Forgot ;
I use the rope in the cylinder trick when changing springs so there is actually something other than air under the valve when I smack it.

That's how I do it. Never even tried the air pressure method. $0.10 in rope is cheaper than any tool.

Thanks for the replies.

Vetteoz; Yes i'm using this exact same one Ive been using compressed air at 90psi. Before attaching air to the spark plug thread, I cranked the engine so that the piston was as close to the head as possible. However when I attached the air, it forced the piston down and rotated the crank! which made me jump back a few feet!

I'm gonna try 84Z28406's trick and use a socket, with air. If that gets me nowhere then i'll try the same with rope so i have something to push against.

Whats the best way to adjust the rockers? I used a 1/2 turn method last time, but as the engine was running with no rocker cover it shot oil everywhere, can you recommend anything better? like a torque setting?

Rockstar

I have seen slip on rocker covers that keep oil from shooting all over the place, most of the oil stays in the top of they cylinder heads and all of it stays in the engine bay.