229/289 carb slide blocks


Active Forum User
VOC Member
Can anyone enlighten me on the significance of the small numbers stamped in the top of Amal standard slide blocks? It seems that the ones normaly installed in 229 and 289 carbs are stamped 58. However I have seen 54 and 18YA also. What is the difference? Would these ones stamped with something other than 58 work in our carbs?