There were at least 3 variants of these. If yours are the racing version they'll be marked as 40P on the transfer port, P was for Pylon. Then there was another marked 40S which was for C/L Stunt and another marked as just 40 which was the normal RC version. I'm not sure but the 40P may have been a twin ball raced crank, the others just use a single ball race at the rear of the crank. Definitely loop scavenged and very nice engines in their day.