Stromberg carb leaking fuel past threads of needle valve

[Will53jgr]

Hi All,

Fuel is leaking past the aluminium washer and the threads of the needle valve where it screws into the body of the Stromberg carb on my S3. At first I thought the needle valve itself was faulty, but the leak is still present with a new valve (and new aluminium washer) in place.

The leak is a steady drip . . drip . . drip. The carburettor is on the car with the float bowl removed and I have wired the fuel pump to a separate 12 volt supply from a remote battery which I control with an enclosed on off switch. Thus I can hold the needle valve closed and run the pump (with a suitable container under the carb to collect drips). This way I was able to see that the fuel drips were coming down from where the needle valve is threaded into the carburettor body and not from the bottom of the valve.

The pump is the standard su double ended, but electronic version

How tight should the needle valve be screwed in? I am wary of stripping the aluminium threads by overtightening, and using a 14mm spanner the valve feels tight.

I searched, but could not find that this topic had arisen before. I did however find the article in the knowledge base by Andrew Turvey (Carb tuning ) which recommended using Loctite on the threads when fitting the needle valve. Has anyone tried this, or any other sealant with any success.

Any help or advice would be appreciated.

[MarekH]

Plumber's PTFE tape will probably fix it.

If you want to use a gasket, then a waxy fibrous one would probably be appropriate. I have just refitted the sump plug onto my fuel tank and a waxy paper gasket with a bit of PTFE tape on the lower threads holds fuel.

kind regards
Marek

[Will53jgr]

Plumber's PTFE tape will probably fix it.

If you want to use a gasket, then a waxy fibrous one would probably be appropriate. I have just refitted the sump plug onto my fuel tank and a waxy paper gasket with a bit of PTFE tape on the lower threads holds fuel.

kind regards
Marek

Many thanks Marek, PTFE on the lower threads of the needle valve and a "washer" cut from gasket paper - no more leak.

[chris420sa]

Given that the top of the float requires adjustment (tab bending) to be at a specified height above the body of the carb, would the float also need readjusting to that height after fitting the washer etc?
Best regards
Chris

[Will53jgr]

Yes, you would need to re-check the float height. I do not know how much difference if any the ptfe tape made to the seating of the needle valve, but the gasket paper I used was 0.25mm and after refitting the valve no adjustment was necessary to the float height.