Intake valve failure

[Rick!]

Has anybody experienced this type of failure before? What's the root cause - fatigue or...?
598 BBM Dragster engine
2.35" diameter steel intake valve
Isky solid roller cam
.750" lift
284/294 @ .050
About 300ish# on the seat, 800ish# on the nose, has PAC springs but I forget the PN.
72-7300rpm engine
about 1200 laps

can you post a pic of an unused new valve??
Just curious what the chamber side of the valve head appears like before damage takes place.

We’re thinking the same thing and I asked my brother for a picture of a new valve.
A little more digging and I think the intakes are only Manley Race Series and they should be the Severe Duty version. (4X UTS over Race Series)

[piston guy]

I offer the "opinion" that the (stainless?) valve "weight" slamming back on the seat with 300lbs of seat pressure is trying to pull the "center" out of the valve . Flex is the most common cause of valves cracking. The bigger they are in diameter the greater the effect. I have only had one valve do that to me but the valve had "too little" spring pressure. Obviously not your situation but the crack was nearly identical.