Before installation, please check you have the correct product for your Stromberg application.

The Stromberg Throttle Shaft Extension kit (9139K) is designed for narrow spaced 4×2 and 6×2 intakes where all of the carburetors are linked on one side. To resist twisting in operation, Stromberg shaft extensions are made of high-grade stainless steel, with a larger diameter section extending as far up the shaft as possible. For improved looks, it covers the 97 throttle shaft bush. And for maximum security and alignment, it can be fixed with a 3/32” roll pin (supplied) through the hand throttle mounting hole, standard on the end of every 97 throttle shaft. Most important of all, each kit also includes a stainless steel ‘trim- to-fit’ bracket to support the free end of the extension, with a PTFE-lined bush for smooth operation.

The 9139K kit will fit intakes with a 3-3/4” maximum offset between right and left banks (See Offset B).
The extension support brackets can accommodate up to 4-1/8” offset between the two banks of carburetors (See Offset A) – enough to fit most ‘known’ intake applications. The shaft extensions should be fitted to the carburetors on the right side of the car (from the driver’s seat). The supports slide onto the extension (with the bush pointing upwards) and mount to the carburetors immediately behind.

3. Fit the throttle shaft extension
Slide the stainless steel throttle shaft extension onto the end of the Stromberg 97 throttle shaft. The extension goes over the carburetor throttle shaft bush so you may need to remove the paint first. The end of the extension should sit snug against the casting, with a small clearance to ensure free rotation. As carburetor castings vary slightly, you may need to trim back the fat end of the extension where it meets the casting to ensure correct alignment of the hole in the extension with the hole in the end of the throttle shaft. Again, always ensure enough clearance so the extension does not bind against the casting. Once the holes align, and the shaft rotates freely, pin the extension to the carburetor throttle shaft with the 3/32” roll pin supplied. Support the end of the shaft when driving the pin.

4. Trim the support bracket

You will need to drill an 11/32” hole to mount the extension support bracket to the 5/16” carburetor mounting stud, then trim the support bracket to length.

On your manifold, use a couple of straight edges and measure Offset A (see above, marked Green) – ie how far the right side carbs are behind the left side carbs. Now take 7/8” inch off that measurement. On this intake, that would be 2-5/8” minus 7/8” = 1-3/4 inch. Yours may be different, of course.

Now take your support bracket and mark out the distance you have just worked out along the bracket from the center-line of the bush at the end. You’ll have to eye that center through but you won’t be far off. Drill a 11/32” hole in the bracket and trim the end off, around 3/8” inch past the CENTER of your hole. Measure twice. Cut once! You may want to round the corners off again, especially on the inside corner as the Stromberg base casting need a little more clearance on that side.

5. Install the support bracket.

With the carburetors on the manifold, slide the bracket onto the shaft, with the bush upwards as in the picture, and fix it onto the front mounting stud of the carburetor behind. Install the washer and nut.

6. Linkage alignment
Linkage alignment is critical to keeping the system bind-free and operating efficiently. Remember, for smooth operation, all your throttle shafts must be parallel to each other and at 90 degrees to the linkage rod that joins them all together. With perfect alignment of all four/six throttle shafts, they will pull smoothly and without bind or mis-alignment.

Intake and carburetor castings can vary slightly, so you may need to adjust each support bracket very slightly to ensure free, easy linkage movement. A small washer between the bracket and the base casting might help with vertical alignment, for example. Or you may need to adjust that 11/32” hole. A little carburetor movement on the mounts may help too.

Use Stromberg linkage parts!
Complete your linkage with Genuine Stromberg linkage parts. You can find the complete range on our website at Simply add a Stromberg Superlink lever with swivel (9091K) to each throttle shaft and join them together with a length of 3/16” stainless steel rod. Stromberg Snapback torsion return springs (9154K) work with throttle extensions too.


WARNING! When replacing carburetors onto the engine, always ensure you have connected all of the linkages – throttle, choke, accelerator pump – and fuel lines correctly. Manually operate the throttle lever and choke mechanism to ensure free movement. Any sticking, binding, or ‘over-center’ movement in the linkage could result in uncontrolled engine speed, property damage, serious personal injury, or death.

You’re done! If you think we’ve missed anything or we could improve on this Genuine Stromberg ‘How To’, then please let us know. Email  –

WARNING: These instructions, including the diagrams and warnings , must be read and fully understood before installation, otherwise installation should not be attempted. Failure to follow these instructions may result in poor performance, vehicle damage, personal injury or death.
If you have any questions, contact your Genuine Stromberg dealer or email us at tech@stromberg- 97

WARNING: Never smoke, use an open flame, or produce any sparks where gasoline or gasoline vapors could be present. Always perform any work on the fuel system in a well ventilated area. Failure to do so may result in the build up of dangerous gasoline or other combustible vapors that may cause severe respiratory injury, or a fire or explosion, resulting in property damage, serious personal injury, or death.
WARNING: The installation of this kit requires some metal fabrication skills. Stromberg recommends that installation be performed only by a professional auto mechanic or fabricator. An improperly fitted carburetor linkage may cause poor performance or lead to property damage, personal injury, or death.
WARNING: Always disconnect your vehicle’s battery and make sure that the engine is cool before performing any work on a vehicle’s fuel system. Failure to do so may produce sparks, causing a fire or explosion, resulting in property damage, serious personal injury, or death.