What can cause a dropped valve??

[RedTsi_PR]

Hey guys!! I was on my way to my local dragstrip today when all of a sudden the engine died with symptom as a broken timing belt but i was adamant because i have a brand new Blue gates,But anyways i open the hood to see that the belt was intact.So i take off the Valve cover and find that the #2 spark plug was beaten to Sh!t and the exhaust valve from that piston was missing/snapped from the half.All of this to me is weird because i have Manley Single and Ti-Retainers and all the valves were OEM.So my question is What can cause a valve to snapped? Forgot to mention im running HKS 272.

 

[BogusSVO]

Improper spring tension, metal fatigue are the 2 main ones.
Excessive guide wear, beat out seats are a couple more.

You have the OE valves? Marked 6T on the valve head.

 

[RedTsi_PR]

Yes sir

 

[joescool2008]

Stuck lifter murdered my engine, i had 1500 miles on fresh rebuild with all new head components and didnt realize a lifter was sticking. "Young guy wanting to hot-rod". Ignored the sound because these motors always kinda ticked, anyways it was hard to turn over by hand was the symptom to look at your lifters. Snapped the top of my lifter off and let a rocker arm loose, which led to sticking open valve with head getting snapped off.

 

[RedTsi_PR]

Mine too was in short words a new engine.Everything was new

 

[BogusSVO]

Well apparently not everything was new if you still had the stock valves still in the head.

With the new Manley Singles what seat pressure was used? Or were they just installed with out checking the installed height?

How many RPMs where you turning when it happened? Made any recent hard pulls?

 

[RedTsi_PR]

Manley's we're installed without verifying seat pressure.Also at the moment of the carnage i was cruising but previously i did a 3th gear pull.