Well, it turns out that carburetor rebuild kits are only about $35-40, and I like the idea of going through it completely, rather than wrestling with a carb in unknown condition. Besides, it's mid-winter. A carburetor rebuild can be done indoors, with time that would otherwise not be available to work on the car.
So, where to start? Well, first of all, what do I even have? The carb is stamped with markings identifying it as a Zenith Stromberg. A little searching online turned up this image and accompanying text:
The Zenith Stromberg CD150 series fitted as stock to later North American market Spitfires. Not the best "performance" choice. Many of the subassemblies are not adjustable or rebuildable. Lots of attached hoses and fittings. Early ZS carbs were manual choke. Later ones used a water heated auto-choke. Also shown here is the giant air filter / thermostatic air control contrivance. [Photo and text courtesy Bob Sykes, taken from his brief writeup on Spitfire carburetors on VTR.org]
Should I replace it with one of the other carburetor options, say, twin SU carbs from an earlier Spitfire, or a Weber model? Nah, those upgrades cost many hundreds, even thousands, of dollars. Let's just get it running and see what we have, shall we?
With that in mind, I did a little looking around for instructions, parts, and so on for the Zenith Stromberg CD150 carburetor. Here are some resources I found.
- Troubleshooting advice from Spitfire & GT6 Magazine
- Zenith-Stromberg rebuild instructions, parts 1 and 2 (apparently scans of factory literature?)
- Some tech tips for the Zenith Stromberg, covering damper oil leaks and unstable idle
- Parts from Moss (with a nice exploded view illustration!), SpitBits, and Victoria British.