A Jaguar/Daimler Series 1, Double Six (V12) from the late 1960s and early 1970s is one of the most impressive classics you can own. The heart of the drivetrain is a set of four Zenith/Stromberg 175CD2 carburettors, together responsible for the right power delivery and the legendary smoothness of the twelve-cylinder engine.
After decades of use or long storage these carburettors often struggle with wear, dirt and leaks. A thorough overhaul is then no luxury, but a plain necessity.
Complete strip-down and inspection
The overhaul always starts with a complete strip-down of all four carburettors. Each unit consists of dozens of small parts: from float needle and seat to diaphragm, throttle spindle and jets. Only by taking them apart completely can every passage be cleaned, wear be traced and the fit of each part be checked.
Vacuum and depression lines
A specific point of attention on the Stromberg 175CD2 is the network of vacuum lines and depression passages. These are often overlooked or blocked by old fuel deposits. Every passage is carefully cleaned and cleared. This is essential for a stable idle and the correct operation of the bypass and temperature compensators.
Main jet tubes and jet needles
One of the most critical steps is replacing the main jet tubes. Over the years these tubes wear, so new jet needles no longer fit properly. The result: a far too rich mixture, poor combustion and excessive fuel consumption. That is why we always press new jet tubes into the housing, so the new needles seat perfectly and the carburettor delivers the mixture as intended.
After fitting new gaskets, diaphragms, needles and jets, the carburettors are set up in sync. We also check the float heights, the operation of the vacuum pistons and the vent lines to the air box.
The result
Overhauling a set of Stromberg 175CD2s is no simple job: with four carburettors and hundreds of parts, precision is the key word. But the result speaks for itself: four carburettors running crisply in sync again, doing their work cleanly and delivering the mixture as it should be. Exactly what a twelve-cylinder needs.
What this job takes
A complete overhaul of four Zenith/Stromberg 175CD2 carburettors is a substantial job. The strip-down, cleaning, replacement of the main jet tubes and careful setting up take 16 to 28 hours of work. Once everything is open and the set has been measured, you hear from us what is needed, with a separate quote to go with it. So you are never in for a surprise. For these engines we always recommend a luxury service kit, which contains all gaskets and rubbers plus the critical wear parts such as jet tubes and jet needles.