Alpha-Tranco Valves & Guides
A cylinder head rebuild is only as good as the valve and guide that go into it. Alpha-Tranco supplies replacement valves and guides for British singles and twins, and we list them by the machine they suit so you can order for the engine on your bench rather than by supplier catalogue number. Valve and guide are best replaced together.
Obsolete Bike Parts stocks Alpha-Tranco inlet and exhaust valves, single valve and guide pairs and complete sets for BSA, Norton and Velocette engines, alongside the valve springs and gaskets you will need for the same job.
Match the set to the engine
Valve head size, stem diameter and length differ between models that look closely related, and guides are made to suit a specific head. A BSA B33 exhaust valve is not a B40 valve, and the Commando 750 and 850 sets are listed separately for good reason. Order by the model and engine number rather than by appearance. If your head has been rebuilt before, check whether oversize guides or different valves were fitted, because that changes what you need. New guides usually mean the valve seats need attention as well, so plan that work at the same time.
Alpha-Tranco sets we list
- BSA singles: B33, M33, B34 and B40 valves and guides
- BSA twins: A7 and A50 valve and guide sets
- Norton: Commando 750 and 850 valve and guide sets
- Velocette: MSS and Venom inlet and exhaust valves
Machining the head?
Tell us which engine the head comes from and what work your machinist plans. We can confirm the right set before the head goes on the bench, and point you to the springs and gaskets for the same engine.