Zenith-Stromberg 175CD-2
Back to basics
Zenith-Stromberg is a carburettor I have extensive experience with. I know these carburettors inside and out: every spring, every spindle bush and every detail of play that makes the difference between a carburettor that really works and one that has already been rebuilt six times without the underlying cause ever being found.
That is how a valuer came to me with his beautiful Volvo 244 with a B23 engine. The car suffered from a persistent air leak — that insidious, hard-to-pin-down phenomenon that means the engine never quite runs as it should. Each time it seemed to have been fixed, only to rear its head again afterwards. Understandably, that causes considerable frustration. To arrive at a definitive solution, it was decided to call in my expertise for a thorough on-site diagnosis.
That is a special kind of pressure. When a problem keeps stubbornly coming back, it does not help to trust blindly in what has already been done. You have to go back to basics and build up again from there, as if you were looking at the carburettor for the first time. I am not dogmatically attached to the idea that something new is good by definition — in a case like this it pays to look beyond that, and to reassess every part rather than rely on a label saying "replaced" or "rebuilt".
It is an approach that gives clients the confidence they are looking for. It turned out to be a deeper-lying detail that had gone unnoticed in the process until then. That is precisely why in-depth experience with a specific component makes such a difference. A 175CD-2 looks simple — an air valve, a needle, a cylinder — but the interplay between those parts is subtler than it appears, and a minimal deviation in one place translates into symptoms elsewhere that send you down the wrong path.
After the repair the car ran again as a B23 with a well-tuned Zenith-Stromberg should: smoothly, with a stable idle, exactly as intended. For the owner, after a long search, this result brought enormous relief, and for me as a restorer a moment like that is deeply satisfying.
Jobs like this show me exactly why in-depth experience with a carburettor makes the difference. Not every problem calls for new parts or the latest technology — in this world especially, it calls for someone who knows the component inside out, and who is happy to start completely afresh when the component requires it. That is the passion I feel for the Zenith-Stromberg, just as much as for every other type of carburettor that lands on my workbench.