I was driving my 98 impreza turbo on 2nd gear till redline i changed to 3rd and at that moment the car started running on 3cyl. I stopped it and removed the left cam cover. Two of the shims were broken and the two valves were stuck open(exhaust if it matters). I changed the 2 valves, shims, buckets and drove my car carefully for a week. Yesterday the exact same thing happened to the same head(exhaust valve), but the other 2 shims were broken.
What can I do to stop braking these things. The rev limiter is 7000rpm not that high.
Here is a pic
http://prikachi.com/images/826/6596826U.jpg

 

What did you set the valve clearances to when you changed the valves,buckets and shims ??
The outer bucket shim can be flicked out and broken by the cam lobe in certain circumstances eg valve float,excessive valve clearance, running anti-lag etc etc.
You can change to STi Version 3~4 under bucket shims and valvetrain or even the selective buckets (no shim) or stop bouncing it off the rev limiter.

Mick

 

Is that you dimitris?

 

Wow, shims twice!

Going by your alias, are you running megasquirt?

 

Broke one on mine, but that was hitting the limtier on the launch control when at a drag event

 

I'm running megasquirt with td05 20g turbo on 1.3bar on methanol/gasoline 50:50. Yes I have launch control and antilag(not that hard). I can't understand why the launch control, rev limiter, antilag are causing this?
It didn't broke the same shims the second time. It broke 2 other which were a little bit bigger than the others. In fact they were pretty tight round 0.1mm.

Is it possible to weld the shims to the buckets?

 

The only way to prevent the shims from being flicked out is to change to under bucket shims or selective buckets.
It may help to set the valve clearances to the lower end of the spec :
Inlet valve 0.152 ~ 0.203mm
Exhaust valve 0.203 0.254mm

Mick