Groaning clutch pedal

I'm having trouble keeping the clutch rod that goes thru the firewall aligned up straight on the clutch pedal. The zbar keeps sliding towards the engine which twists the firewall rod crooked and then it makes a big snap on the pedal when it is depressed. Has anyone ever shimmed the zbar out from the eng ball stud with washers to lessen the side to side travel ? How much travel do you need for eng movement ?