‘D’ Type Overdrive- Spitfire Mark III & GT6

Laycock Engineering have modified the non-return valve to prevent malformation of the valve seat.

The non-return valve spring, Part Number 513207 (CT.29 GT6 catalogue) is superseded by a new spring, Part Number 514889 (CT.30) is no longer required.

Therefore, it is necessary to remove and discard the support pin before fitting the new spring.