Alfa-6 valve gear
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I have been taken to task by no less an authority than Graham Robson over my suggestion, last month, that the Alfa Romeo vee-six engine has valve gear like that of a Triumph Dolomite Sprint, so some enlargement is called for. What I was saying was that both engines have ingenious valve gear, inasmuch as there is an economy of rockers and rocker-shafts by arranging for the o.h.-camshaft to open the inlet valves direct and only the exhaust valves by remote means. The omission of brackets in the relevant sentence did not make it clear that while the Alfa Romeo engineers achieve this mechanical economy by the use of horizontal push-rods and small rockers engaged by these push-rods, to prod the exhaust valves, as an illustration made clear, on the Dolomite Sprint four-valve-per-cylinder engine normal rockers open the exhaust valves. Either way additional rockers and rocker-shafts, as would be needed with a single o.h.-camshaft mounted centrally, are obviated, although Robson suggests that the Triumph method reduces the opportunity for lost motion. I saw the Alfa layout as possibly the more sophisticated because it is more compact and its push-rods and small rockers are possibly lighter than having conventional rockers.
Robson has drawn my attention to the 1924 14/45 Rover engine designed by Peter Poppe, as being more closely allied to the Alfa Romeo design than the Triumph Dolomite Sprint engine. I was aware of this, and have referred to this unusual Rover more than once in Motor Sport, but I do not suppose this influenced the Milanese drawing-office, and I preferred a more modern comparison. Nor was the Rover valve gear quite like the system used on the Alfa 6, as rockers were used to actuate the inlet as well as the exhaust valves, thereby removing the point of placing the single o.h-camshaft adjacent to the inlet valves, and before the year of the Rovers announcement was out one letter-writer to a weekly paper had criticised this complication. Lecture over — and my thanks to Graham.
W.B.