[DocJohn]

Hi Alastair, I've been trying to do the same and date my British 21 stud engines. I've not found much documented information and have had to piece together what little I do know. There's a number stamped into the inlet manifold face above number 8 cylinder. It should start B18F and may have some stars. I don't know what the stars mean but the B denotes British built, 18 is the 221 21 stud engine and F means that it is for right hand drive applications, even if it was used in a pump or generator. There will then be a 7 digit number. I've got a late'50/early '51 engine with a 513xxxx engine, and a possibly 1954 engine with a 580xxxx number. I've also got an engine that may have been rebuilt in period and has a completely different set of numbers and letters! Good luck, John