Cutting valve seats in a 1930s Bentley head The cylinder head and block are one piece on this engine - aircraft style. Valve guide and seat work can pose problems but we at Paynes have been working on these engines since they were new! Building up a Rolls Royce 20hp 'six engine'. Having carried out the specialist white-metalling and line boring, we can now proceed to re-assemble the crankshaft into the crankcase.