Cambelt movement
 

What is an acceptable amount?

Backstory. I'm chasing an irritating engine resonance/vibration at 3.5-4k which occurs both in and out of gear or load/no load.

My engine is reclaimed from an accident damaged car, and the upper plastic cambelt cover is slightly damaged, the plastic was pushed onto the belt and wore a hole in it, (the plastic). When fitting the engine I replaced the belt, WP etc). The engine otherwise is perfect, burns no oil, smooth etc.

When trying to find the source of this resonance my Dad noticed that the cambelt seemed to be vibrating a lot at that point, he was looking through the hole in the cover. but I don't know if it's normal. The hole is on the intake side on the upper cover just above the idler pulley area. The belt seems to be deflecting a good 2cm each way if not more.

I plan to take everything apart this weekend anyway, but thought I'd ask if it sounds normal whilst I'm sat at work pondering :)

Cheers