Pair of S.U. H6 Carburetors for Jaguar XK120
SU H6 carburetors are the quintessential fuel delivery system for the Jaguar XK120 (3.4L). These 1.75-inch bore units are part of the “H-Series” (Horizontal) family and are distinctive for their side-mounted float chambers and “Thermo” (automatic enrichment) starting carburetor.
Listing Details
- Pair of S.U. Carburetors
- H6 Carburetor Bodies
- Part #466 Plus Etched #9
- E11 Date Codes
1. Identification and Specifications
For an XK120, you are typically looking for a “Twin Thermo” assembly.
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Main Body Casting: Usually stamped with 466 on the side.
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Specific Etchings: Original factory units often have 9/1 (Front) and 9/4 (Rear) etched onto the top mounting flange.
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Needles: The standard factory needle is usually marked RF (or SJ/SL on later XK140 variants).
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Dimensions: The intake side (air cleaner) is 1.625 inches, while the outlet side (manifold) is 1.75 inches.
2. The “Thermo” Starting Carburetor
The XK120 uses an auxiliary “starting carburetor” (often called a Hiscock device) located between the two main H6 units.
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It is controlled by a solenoid and a thermostatic switch on the intake manifold.
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Common Issue: If your car is hard to start when cold or stays at a high idle when warm, the solenoid or the needle inside this third “carb” is likely stuck.
3. Purchasing & Restoration Options
If you are looking for a pair today, here is the current market landscape:
| Item | Estimated Price (USD) | Notes |
| New Reproduction Pair | $2,100 – $2,500 | Fully assembled units from Burlen Fuel Systems (SU UK). |
| Used/Core Pair | $400 – $800 | Likely require a full professional rebuild and rebushing. |
| Master Rebuild Kit | $350 – $450 | Includes spindles, butterflies, jets, and gaskets for both. |
| Service Kit | $100 – $150 | Basic gaskets and needle valves for a tune-up. |
4. Expert Tip: The “Sticky” Spindle
The most common failure point on vintage H6 units is wear in the throttle spindles and bushes. Because the carb bodies are aluminum and the spindles are brass/steel, the holes eventually become oval-shaped. This allows “false air” to leak in, making it impossible to achieve a steady idle.
Note: If you can wiggle the throttle linkage and see the RPMs change, you need to rebush the bodies.
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