Solex Z10 on B172.
I have just cleaned up a carb for a V3Mer - to replace his original and - the air cleaner doesn't fit!!
Look at the two pictures below,
The original carb,

The carb I rebuilt - note the extra casting on the side of the secondary venturi,

Air cleaner housing has no cut out to accommodate this.
Again, the rebuilt carb,

Suggestion - rebuilt carb not Volvo? - not so - the carb from my Redline, also has extra lump!, (and rebuilt carb still had Volvo exchange sticker on it)
My Redline unit,

I also have 3 other Z10s - a "scrapper" , a NOS exchange unit, and a brand new unit all have this casting.
So, is the "original" carb Volvo - well yes, and the air cleaner fits.
Conclusion, there are certainly two versions of the Z10' but are there really two air cleaner housings???
Observations please people!
Mac.