When I purchased my Fastback with dual CD150's they weren't in very good tune. I researched the inet and dismantled both carbs replacing the diaphragms, etc., Whilst researching I found on an MG forum in Canada the words "When replacing depression chamber cover, the damper ventilation boss MUST be towards the air intake". There must be a reason for this?? I have searched every known publication on CD carbs and have never seen this statement before. Looking at other CD150 twin-carb installations I have noted that the ventilation chamber points in as many directions as can be possible. (four, to be exact) I believe that it is probably correct so that it aligns with the chamber entry on the air cleaner end of the carb. I had my carbs tuned professionally and the car runs perfectly but I am still curious. Any thoughts would be welcome.
Thanks Hillman, just what I had thought about the statements. I was writing an article for my Club Magazine and a lot of "old timers" agreed with me, but most "newbies" hadn't heard of this requirement. I feel very vindicated, thank you so much for your time in providing an answer to my query.