Waxstat jets are big silver things that self adjust the mixture as the engine warms up. Unfortunately these are made of a coil of thermolastic (?) wire and eventually stop working messing up your mix all the time.
These are standard fitment to TR7s so its likely you will have them. I would reccomend converting them to the earlier red coloured TR4 style fixed jet for reliability. Also remove the sticking poppet valves in the throttle butterfiles and replace with solid butterflies , again from the TR4. Andy Turner sells the kit cheaply at
http://www.su-carbs.co.uk/
Here's a picture:
<b>Fixed jets on the left. Waxstat on the right.</b>
<b>Also here you can see the poppet valve in the butterfly on the left and the conversion to solid butterfly on the right:</b>
<b>Red 4.0 Litre V8 DHC Grinnall (with huuuuuge arches...!)</b>