190sl Solex 44 PHH Carburetor Rebuild
The Daimler Benz development team back in 1954 choose the Solex 44 PHH hotizontal two-stage carburetor, which is still the topic of heated discussion today. The image that the Solex 44 PHH have gained, the lack on knowledge and for other reasons caused owners to subsitute these for non-original Webbers or Makuni's. Is it really as unreliable as is often claimed? Well I was about to find out since I have decided on a point of ogriginality to rebuild these units.
On reading up on this subject it appears that problems did not start with these untils until a full three decades latter. It was only in the nineteen-eighties that the 190SL owners became increasingly disillusioned and the rumor that the 44 PHH was temperamental and rather prone to malfunction.
Listening to carburetor faults as voiced by other members, restoration shop's and technical articles, I drew up a list of problems. Naturally a complete overhaul with these faults in mind was needed to ensure that my Solex's run smoothly:
1. Loose throttle shafts - As they are mounted directly in the engine casting the radial lash causes an excessive amount of air to be admitted ot the engine. As a result ideling remains at a level between 500 and 2,000 rpm and can not be adjusted.
2. Distorted housing - As a result of the engine's rough idle and ride the carburetor was shaken loose. This was further tributed by the strut which supports the induction pipe often missing. This strut is required so that its entire weight does not have to be borne by the carburetor flange. Washers between the carburetor flange anf the rubber flange are often omitted during repairs. If the washers are missing, the bolts are invevitabley drawn too tightly, which in turn causes the flange to warp and requires machining and fabrication of largely dimensioned throttle valves.
3. Worn ball neck heads - These are often simply worn or the linkage can be out of adjustment. These problems are easily rectified at little cost.
4. Second-stage linkage - This linkage and follower are also susceptible to faulty adjustment. From 3,500 rpm upwards this linkage should open the second stage throttle valve as a result of the breakdown of venturi vacuum that sets in at this stage. If it does not have the necessary 1/10 millimeter clearance when closed, this function is not guaranteed.
This first photo shows the condition of one of the two carburetors before overhaul.
After two hours of stripping, cleaning and glass blasting this is what the bodies looked like.
I then checked every part and ordered new rebuild kits from Ron Rapp as service parts are no longer available from Mercedes Benz. Every nut, bolt, bracket and screw was yellow pasivate plated using a kit from Frost Auto Restoration.
