Flywheel Bolts- Spitfire

October, 1972

A different type of material has been specified for the manufacturing of the flywheel attachment bolts fitted to four-cylinder Triumphs. The change of material affects the tightening torque requirements. Please not that the part number remains unchanged (138526). The new bolt, however, is quite different in appearance and is easily identified.

Bolt AppearanceTypeTightening Torque
Black (Parkerized finish)Original42 to 50 lb./ft.
Bright (Cadmium plated)Revised35 to 40 lb./ft.

Please advise your workshop personnel of the tightening torque requirements.