Date registered: Jan 2013
Vehicle: 90 350SDL, 98 S420, 97 SL500, 94 S420, past owner of W108/W112/W114/W123/W124/W126/W140 & W220 cars
Location: Tampa, FL
Mentioned: 8 Post(s)
Quoted: 607 Post(s)
I had a 123 long wheelbase sedan in the early 2000s with an M123 engine with the Solex 4A1. A cursed carb if there ever was one (and this is coming from someone who loves the dual Zeniths on earlier models!)
Nearly every one you might find will have a warped top cover - it's a fault they all develop regardless of how they are cared for.
I searched high and low for them, and the best I could find was a rebuild from the UK, but it was still easily $500 plus shipping.
I do know of a brand new, in the box carb that's in Australia, however. Not sure it's for sale, and if so, how much. If you're interested I can put you in touch with the owner - just PM me.
The alternative is to go with a conversion if yours gets wonky. I used a Holley 5200 with an adapter plate, and it worked quite well. I know of others who were able to adapt a Quadrajet to these as well.