With regard to the 3-litre double o.h.c. Armstrong-Siddeley, I can confirm that this car was indeed designed by W.O. Bentley. I was employed by Armstrong-Siddeley Motors from mid-1949 to mid-1953, in the aero-engine development division, but as it is not a very big factory the car and aero-engine people all knew each other and the car parts were machined in the same shops as the aero-engines.
The 3-litre double o.h.c. bore a superficial resemblance to the 2.6-litre Lagonda and Aston-Martin engines but there were detail differences. There was a closer likeness to the 4-litre (?) straight-eight engine built by Henry Meadows Ltd. for the Invicta Black Prince. This was also designed by W.O. Bentley.
When I was at “the Siddeley” work on the Bentley engines had ceased and the 3.4-litre Sapphire development was being finalised. Three or four twin-camshaft engines had been built and two chassis I think Mr. Bentley was only responsible for the engine. One complete car which lurked in the car experimental fitting shop for about two years of my time at Coventry was sold for a modest price to one of the people at Gloster Aircraft an associated firm in the Hawker-Siddeley group. And as the remaining engine was going to be scrapped I asked Colonel Siddeley, the Managing Director of the Car Division, if I could have it. He gave it to me for a nominal sum, and included a Cotal gearbox which had been built for the car (by Armstrong-Siddeley). I also secured some spares from previously scrapped engines, and still have two cylinder heads and a crankshaft. My special-building project failed for lack of money, time and space, so my engine went for scrap about five years later.
The engine was said to be reliable after some initial troubles had been rectified notably, insufficient oil drainage from the valve-gear, and insufficient take-up on the timing-chain tensioner (a single duplex chain about 6 feet long can stretch quite a lot in a short while), but it was not very powerful. It was limited by Pool petrol of course, but even so 95 h.p. was a bit meagre. If you fitted an exhaust camshaft on the inlet side you got rather more. But I think it was intended to be a gentlemanly touring car, and the timing was very soft.
I think W.O. and Donald Bastow had a drawing office in Birmingham and possibly other projects were under way, but unless one of these gentlemen preserved some records it would be difficult to get any details.
Finchley K. G. GILLING