My roommate dropped a valve in his 5.0 F@$D this weekend.He just installed a smaller pulley on the supercharger last week and coming home Friday night he ran it up over 6500RPM and BLAMMO- that was that.We figure his springs were too weak and at that RPM, they started to float the vlaves...

He was surprised he didn't break a piston before the valve bent because he has cast pistons in this motor.Not only did the valve get bent, but the valve guide in the head split in 3 places...

What happens to the valvetrain during valve float? Does each cylinder of valves operate independently from each other, or if a valve starts to float are they all floating?Also, what effect on compression to each cylinder does this have?When the one valve crashed, what kept all the others from going as well??

I hope I explained this well enough because we are not looking for the cause of valve float, but the effects of valve float on the valvetrain/and each cylinder of an engine..

Valve float is basically when your engine is spinning beyond your springs capacity to fully close the valve in the time before its it supposed to be opening again. Meaning that becuase your springs are not closing your valve they are staying open a little, and you are loosing compression or blowing exhaust out your intake valves, etc depending on the stage of the engine.

Each cylinder has the same springs and runs off the same cam. Valve float can happen differently among intake and exhaust valves, because intake valves are larger and heavier, which require more force to move and therefore float easier. If one among your intake or exhaust as a group are floating the rest probably are to. They are all on the same cam, and use the same springs.

The danger of serious valve float like your friend experienced was the piston contacting the valve. This happens becuase the valve isn't where it is supposed to be in relation to the piston at a given time in the engine cycle. The valve being out of place, or not closing completely causes piston to valve contact. That or extreme rod stretch from over revving. Hope that answers your questions.

Daniel

Daniel, thanks for the explanation- that was just what I was looking for..It was an intake valve that dropped due to the spring failure.I knew that the springs were the same and that they are running off the same cam.So when the first intake valve dropped and bent, did it have any effect on saving the other valves from dropping by either the change in compression or the disturbance it caused on the rest of the valvetrain, or was it just dumb luck.

I was of the opinion that the valetrain works as a complete unit- the opening of one valve using the force of the closing of another.
My buddy seems to think that they are seperate units for each cylinder and one cylinder's valves has no effect on the other cylinder's valves...wich is correct?