This valve prevents the "running-on" of the engine after the ignition is switched off when, due to the heat of the engine, a condition of compression ignition or dieselling is set up.

The method of achieving engine cut off is by applying a slight manifold vacuum to the float chamber of the carburettor when the ignition is switched off. This prevents fuel from flowing from the float bowl to the carburettor henceforth stopping the engine.

All the original complaints about STAG Cooling system were probably justified and usually related to the fact that the sand cores was not always fully removed from the engine block after casting, and in use, ended up in the radiator. The other real problem was/is that the internal water pump is high in the block and if the engine has slight water loss, then the pump is left high and dry, the water starts to boil around the heads.

Steering Rack - Swaps and Repairs 

Whilst they may look the same, most Triumph steering racks cannot be successfully interchanged without some level of modification. In recent years, the most prevalent example has been using a late model T2000/2500 rack when converting a left-hand drive TR6. This article discusses the origins, repair, conversions and modifications for race use, and particularly shows why such conversions are usually done wrongly.