valve cover and spring pressure

[Racer-71]

Is it very common for the check valve in the valve cover to break off in the upper cavity, had one come loose this weekend , just thought it was weird for this to come loose, and this is on a unrestricted animalnot sure what cam is in the engine, but could someone give me a rough idea what my spring pressure should be,
thanks for the help

 

[Jimbo]

It's not common for the valve to break.
On a new head with out any grinding of the valve seats and with aftermarket springs the pressure will be around 20 lbs on the seat.

 

[Gonzari]

We've seen the pressed-in plate loosen on occasion, and come out, resting on the rockers. I've pressed it back in, no problems afterwards. As for the spring, unusual for it to fail, but have seen debris hold it open, leading to oil blowing out the rocker cover hole.