Mark IV petrol valve

I am working on the reserve fuel valve for my Mark IV. I have heard the Alan Gibbons rebuilds these valves. Does anyone know his contact information? My car was last on the road in 1960. It doesn’t seem sporting to bipass this valve.

Alan’s email is:
alan"at"ssjaguar.co.uk

“at” = @

Yes, I learned back in May that the seals are cork.

I used some fuel hose with an o.d. to match the bore. Care had to be taken to face off the ends to be flat and square to the sides, and the right length to enable compression of the sides. This method has been in operation now for over seven years and works perfectly at both positions.

Just a few tips:

  • The retaining screw is obvious on the outer casing and the blank (unthreaded) tip is important to stop the piston from rotating. Don’t strain this part as you don’t want to break off this fragile end. In other words, don’t twist the control knob with any force, e.g. tightening the lock nut.
  • The locking screw for the centre rod is not as easily seen but must be removed before disassembly of the seal piston. It is very important as it locks the centre rod in the correct position after compressing the seals sufficiently to prevent gradual unscrewing in service. Don’t lose it or break it.
  • Trial and error is needed to test the amount of compression of the seals needed to find the ideal balance between too tight and too loose.
  • Make sure there is no leak as it is possible to slowly drain the tank one drip at a time if you are not using the car for some time. (I know, it happened to me before a rebuild. The leak was so slow that fuel odour was almost non-existent.) Check it every day for a while and hold the tap in both positions in turn for leak testing. This tap is lower than the tank and all petrol can be lost.
  • The original cork material may work better than rubber with less ‘drag’ in the cylinder, but the product was notorious for shrinking.
  • A modern cork compound is likely to be far more stable but I have no experience with this.

As an aside, I am trying to rebuild an old one but a previous owner deftly brazed the body and the end of the piston and its lock screw together. It would be easily corrected if it had been soft solder or even silver solder. Ah well, such is life.

My car ( currently with tank out being sealed/ rust proofed ) has no reserve/ main valve ( or the connection to the knob on the fender). Anyone in the market to part with one?
Is it a pull or a twist to switch over?

Pull engages the reserve.

Peter