In “Vintage Postbag” Geoff Healey mentions the twin-cam 3-litre engine designed by W. O. Bentley for Armstrong Siddeley. I was certainly much concerned with the 2.3-litre Siddeley engine, but I was also engaged upon carburetter work on the 3-litre as well. I drove the car quite a bit, usually in company with Mervyn Cutler or John Densham. I believe twin SUs were originally used, but Mr. Allard wanted to use a single Stromberg, as with other Siddeley models. He designed an extra two-port tract, which bolted onto the manifold ports used by SU. Because the new system looked a lot of cold induction, I suggested to Mr. Allard that a hot water jacket round the new portion might be beneficial, and I believe this was done. I cannot trace copies of any figures.
I can add a little more to the general history of the project. According to my note at the time, the first car I worked on bore not the Cotal gearbox, but a Wilson box with Newton centrifugal clutch. I noted that the clutch permitted the engine r.p.m. to rise too high before engagement, rather apt to cover-up any possible flat-spot, which I believed to be cheating. I recall being present at several meetings with W. O. and Donald Bastow. But in the late ’30s I had worked with W. O. on the carburation of the VI2 Lagonda. Then, Brooklands was still functioning, and, as Lagonda used it for testing, I was glad to get in a little Brooklands driving before the track was demolished.
I do not believe “Sammy” Sampietro had anything to do with the 3.4-litre Sapphire engine, but believe Charles Goodacre did. I myself was responsible for the carburation,
with both single and twin Stromberg carburetters.
Strewley Common C. H. FISHER,
CEng., FIMech.E, MSAE
[Mr. Fisher is the well-known carburation expert, whose erudite articles I used to read in The Automobile Engineer, etc. – Ed.]