New engine tragedy, Broken valve stem Options

[Jetsetsurfshop]

On my first outing with the new engine tragedy struck. While giving it a little bit of RPM the engine made a noise I never heard before and then dropped a cylinder. Limped it home and this is what I found today.
That's the top of the valve you see still with the keeper! Damn.
Anyone have any thoughts on what happened here?
Everything we did was the same as the last build except we installed a more aggressive camshaft.
(IMG:style_emoticons/default/headbang.gif)

[HAM Inc]

The valve breaking in that position is a classic symptom of valve float and launch and/or coil bind. With a big heavy valve and aggressive cam all of those situations can occur at the same time.

The spring may not have been in coil bind at lower revs, but a heavy valve and aggressive cam can easily put a valve in a launch condition.

What were you turning it when it let go?

I noticed in the pic that the keepers appear to butt, meaning they are floating in the keeper grooves. That will contribute in a big way to this type of failure in a valve float, launch situation.

If those are the springs I think they are they are very unsuited for 48mm valves and an aggressive cam when fresh, much less when they have some hard track miles on them. Around 15 hours of hard track time is max for them. They typically lose around 8-10% of open pressure by then.

A failure of a rocker and valve at the keeper grooves is almost certain to be preceded by float, coil bind or geometry problems. Generally all of the above happen when a major misapplication of components occurs.