Three S.U. Carburetors and Intake Manifold for Jaguar

A triple SU HD8 (2-inch) setup is the “Holy Grail” for Jaguar XK engine performance. While it was standard on the Series 1 E-Type and the Mark X, it is a frequent and high-value upgrade for owners of the Series 2 E-Type (replacing the twin Zenith-Strombergs) or those building an “S-spec” XK150.

Listing Details

• Three S.U. Carburetors
• AUC 7090 HD8
• Aluminum Intake Manifold
• Fits Jaguar 4.2L Inline-Six
• Throttle Linkages

1. Identifying the Setup

A complete triple SU kit for a Jaguar consists of five major aluminum castings and three carburetors:

• The Three Intake Runners: These individual manifolds bolt the carburetors to the cylinder head.

• The Water Rail: Connects the tops of the manifolds to circulate coolant and houses the thermostat.

• The Air Balance Pipe: A long, thin tube that connects the three intake paths to stabilize the vacuum across the engine.

• The Carburetors: Typically SU HD8 units. These are 2-inch “Heavy Duty” models with the signature brass damper nuts.

2. E-Type vs. Mark X / 420G Manifolds

If you are buying a used setup, fitment is the biggest hurdle. The manifolds look nearly identical but are not interchangeable due to hood (bonnet) clearance.

• E-Type Manifold: The runners are cast with a slight “downward” angle. This drops the carburetors lower to clear the E-Type’s low-slung bonnet.

• Mark X / 420G Manifold: These runners are straight or slightly angled upward. If you try to fit a Mark X setup into an E-Type, the “dashpots” (the tall bells on top of the carbs) will hit the underside of the hood.

• The “Hisser”: Mark X setups often include a “Thermo” starting carburetor (the hisser) located between the front and center carb. Most E-Type owners block this off and convert to a manual cable-pull choke for simplicity and reliability.

3. Market Value (2026 Estimates)

Prices have risen sharply as more owners look to “de-smog” their Series 2 cars.

4. Technical Checklist for Installation

• Cylinder Head Compatibility: To use a triple SU setup, your engine must have a “Straight Port” cylinder head (found on 3.8/4.2 E-Types and Mark X). If you have an earlier “B-Type” head (common on MK2 sedans), the port spacing is different, and the triple manifold will not bolt up without a specialized adapter.

• The Linkage: The throttle linkage for a 3.8L engine is typically top-mounted, while the 4.2L linkage is bottom-mounted. Ensure your kit matches your car’s accelerator pedal setup.

• Needle Selection: If installing on a 4.2L engine, the standard needle is usually a “UM”. For a 3.8L, a “UE” is common. If you have modified cams or a high-compression head, you may need a richer profile like the “UV”.

5. Maintenance Tip: The “Drop Test”

Before installing used carburetors, perform a “drop test” on the suction chambers:

1. Remove the oil damper from the top.

2. Lift the piston to the top of its travel and let it fall.

3. It should fall smoothly with a distinct “thud” at the bottom. If it hangs or falls too slowly, the piston and bell are no longer a “matched pair” or are warped, which will cause erratic idling that no amount of tuning can fix.