Compressed air or TDC method for valve spring removal
Iv always used air because it really helps with a stuck keeper or a if the valve drops down like the pic above you will have a hard time fighting a "floating" valve. As far as the crank turning when air is applied, if you aren't a re re and leave the breaker bar on the crank bolt it makes no difference at all. Who cares if the rotating assembly moves....it wont hit you...I promise lol
You will hear all sorts of hissing coming thru the holes in the head that lead to the bottom end. That is normal as it is blowing past the rings.
And as a side note I always take a larger socket suck as a 3/4 or so and place it on the edges of the retainer and smack it with a hammer. This sorta shocks the keeper to release it being stuck to the retainer. Iv never had one fly off or any crazy stuff like that.
Just like a earlier post. Its just hot rodding.....dont over think a valve spring.
You will hear all sorts of hissing coming thru the holes in the head that lead to the bottom end. That is normal as it is blowing past the rings.
And as a side note I always take a larger socket suck as a 3/4 or so and place it on the edges of the retainer and smack it with a hammer. This sorta shocks the keeper to release it being stuck to the retainer. Iv never had one fly off or any crazy stuff like that.
Just like a earlier post. Its just hot rodding.....dont over think a valve spring.
When I'm under the hood, I don't want anything moving unintentionally... 
Been hot rodding for50+ years. Always use a rubber mallet to strike the top of the retainer prior to removing the valve keepers. I have never been hit by a keeper. This isn't rocket science it phuchin hot rodding. Don't over think every little thing that you do. Nuff said.
Through the top was on a 2JZ-GTE supra engine.
