Always be careful so that when you take the valve keepers off that the valve does not fall down in the cylinder. You have to hook air to the cylinder by using a plug that will fit your spark plug hole on the one your working on to keep the valves up in the head. I have used air in the past but found that if I make sure that each cylinder that I'm working on that the piston is TDC then the intake or exhaust valve will not fall down in the motor. The valve will just slide down and rest on the piston.You just got to make sure you do not turn the motor over at all. I put rags over the oil travel holes in the heads so if I drop one of those valve keepers that it will not go down into the motor. Oh yeah you will need a valve spring compressor. lol