I know what valve float is. But what causes it, how do you diagnosis it, and how do you eliminate it?

I was talking to a sponsor about my future mods, and he said that the flat hp curve above 5000 rpm that I have could be experiencing valve float. I just want to eliminate any potential problems before I do more mods.

 

When the valve springs aren't strong enough for the cam, you'll get to a point where they don't close quickly enough.

 

your lifters will fail to recoil quickly enough because the pushrods make their cycle and are trying to push the lifter up again.so the valve is pretty much held in the open position. get some comp918's or something

 

Exactly what Rhino said but to expound on it more: the heavier the valvetrain components, the more aggessive the lobe of a cam and or higher rpms, the heavier the spring you will need.

Vinci 062
DUR @ .004" 272*/280*
DUR @ .050" 210*/218*
LIFT .551 / .551
OVERLAP 52*
LSA 112*

If you have stock springs with this cam you will most likely get valve float.

 

i never recieved valve float with my 02 LS6 cam

 

Forgot to put in my original post that I have Crane dual valvesprings with titanium retainers rated to .650 lift with stock rockers.

Could the wrong length pushrods attribute to valve float? I was running hardened 7.4s with stock heads, and went to 7.35s with my new heads which are milled .045. Could that be affecting anything? What if I tired some 3.775 pushrods?

 

maybe, float could be caused by pushrods too longb but i cant see how the difference would be that great with that cam but i dont know much about dual set ups

 

IMO you arent experiencing valve float. Those things have something like 500#s of pressure at bind. I dont think your pushrods are the cause either you are just about perfect, you have a little more preload than stock which should help with the sewing machine sound but its not too much that it would kill a lifter. I would have to have the base circle diameters of the stock cam and the Vinci cam in order to tell you exactly what length pushrod is "optimum" but IMO oyu are pretty damn close.

 

yeah, you shouldn't be getting any float with your set-up and valvetrain geometry shouldn't affect float.

 

i'm not sure if this is right, but just to throw in there, maybe those valve springs are too stiff for that cam.