[94' SSE L27 series I] Knocking on idle

[Mcmaker]

Hi. I recently bought my first Bonnie, it was love at first sight, but love as love it have some issues. The biggest one it's the tinny knocking sound coming from the top center of the engine (where the plastic intake manifold is) and only when engine is on idle. When I rev it to about 2000 RPM it goes quiet and it seems to me that if i heat up the engine knocking sound becomes slightly quieter
Can you help me?

[RJolly87]

Does it sound and act like this? https://www.youtube.com/watch?v=zTaDCd4 ... l=rjolly87

[Mcmaker]

Thanks for fast response! Not exactly the same noise, but similar and it behave exactly like this!
I'll check if this knocking still occurs without belt

Edit: I have a major leak of oil under the harmonic balancer. What it could be caused by?

[MattStrike]

An oil leak at the balancer usually means the balancer seal on the timing cover is worn out and needs to be replaced.

[Mcmaker]

Double checked the harmonic balancer today and unfortunately it's ok. I made poor quality video, but you can clearly hear that knocking on idle, and like i said it's coming from the top center of engine, and goes away at about 2000 RPM.
Don't worry about not-so-nice engine smoothness, it's caused by bad LPG injectors, on petrol everything is ok.

https://www.youtube.com/watch?v=Qwnzm8JDxeY