Putting the bottom end together for a friend; 1955 Shooting Star.
Just completed modifying the anti-wet sumping valve to improve the performance.
In my opinion the existing spring is too light, and exerts insufficient pressure.
This is confirmed by BSA's change to the A65, where they used a much heavier spring for the same role.
I replace the existing spring with the A65 spring. I also make a modified retaining screw. The overall length is increased to approx twice the original (0.285"). This is to increase the thread contact in the casing in order to stop oil leaking past.
A 3/8"BSW tap has to be used to increase the thread depth (a couple of threads).
I use Loctite 569 (hydraulic sealant) on the thread as well. Finally the spring side of the screw is countersunk 0.120" to centrally locate the spring, and ensure that the ball moves completely below the oil supply hole to the bushing, when coil bound.
The ball needs to be lightly tapped to re-seat (no more than a tap!).
The ball seat pressure is significantly increased, and there is 0.3" movement of the ball away from the seat.