18-04-2019, 08:45 PM
The 9C may be our clue to parentage of the casting, the grey matter is not as good as it was, but if I recall correctly the competition conversion parts were all originally numbered 9C later they were numbered 9E, much like the XL and IA numbering on std components. ( not sure when the change took place but could coincide with std components around 1927) However unlike the std components the 9C parts always carried the same prefix even when they remained in use after the introduction of the 9E numbers, all very academic I know but I find these things interesting. As you may recall I did a study of early std LC heads and found at least five different combustion chamber shapes and volumes all on unskimmed heads. I see no reason why the factory would not make subtle variation on the chamber of competition heads when used in a different application, i.e Brookland's, Super Sports, and blown Ulster. I anticipate we will see the same 9C number on all three and will be interested to see if I am right or wrong in my assumption.
Black Art Enthusiast