Does he say “racking on your pal Crawford”? What does “racking on …” mean?

From context he is saying the guy is giving information that the other guy would be mad about. This is called "ratting" or to "rat out". I tgink the british accent confused the sybtitles writer and he is in fact saying ratting if you close your eyes and listen.

Because of his accent, which is overly enunciated and theatrical, I think the auto-generated subtitles are mishearing the overly-pronoucned "t" sound from "ratting" as a "ck" sound instead. It sounds like ratting to me (I would pronounce it with a much softer "t" and "ing" sound, closer to "radt'n", but I'm not a mid-century actor), and given the context, that makes the most sense - "ratting on" means "betraying your fellow rule-breakers to the authorities." The other phrases he uses in context back this up: "turning King's evidence" means "officially testifying in a court of law" and a "squealer" is someone who alerts the authorities to a crime.

He's not saying racking on, he's saying ragging on, which means to tease or make fun of.