Solved NIC#787 - Willis Special (based on BMW 315)

[nicanary]

What was this car called, and on what car is it based?

[nicanary]

Experts?

[Allan L]

Well that's the startline at Prescott, probably in the 1940s.
That's the BMW-based car which was known by its maker's name as the Willis Special.  I last saw it being raced at Silverstone by Proby Cautley in 2005 or so when it was declared as 1971cc.

[nicanary]

Well that's the startline at Prescott, probably in the 1940s.
That's the BMW-based car which was known by its maker's name as the Willis Special.  I last saw it being raced at Silverstone by Proby Cautley in 2005 or so when it was declared as 1971cc.

Yes indeed. In fact I thought this had been a previous puzzle, but I can't find it using the search.

Built by Ron Willis on a 1935 BMW 315, but I believe it was later fitted with an engine from a 328.

[Allan L]

I knew a man who would have known, namely Charles Bulmer whose wife was Ron Willis's daughter. Both dead now so we're left with speculation.
In theory a BMW 315 was a (58 × 94) 1½ litre but (according to Werner Oswald) the 319/329 (also available in 1935) was 1911cc (65 × 96). That extra mm of bore to give 1971cc came in with the 320, but without the 328 valvegear.