Few reasons of knocking
Bad Quality Fuel.
Distributor adjustment is very very sensitive thing to do. If its settings are advance or late, it seriously affects combustion.
My car distributor start leaking bit of oil. I changed it ring, the mechanic couldn’t successfully adjust the same position of distributor as it was before. So my car start knocking too even with 100% hioctane.
I went back to mechanic and asked him to adjust it again. He did, knocking reduced but yet not gone fully. I went again. Eventually after couple of times distributor adjustments, finally its OK now. Even on regular fuel its pick up is like rocket.
Here 100% mechanics do this settings manually. Never heard if someone is doing distributor settings with some machine or with some other instrument. However its v. v. v. important.