& per T-C's recent interest in sleeve valve engine merits*, I found this Bristol TBO in a period 'Flight' article..
https://www.flightglobal.com/pdfarchive ... 01350.html
* The linked forum thread which included a Kiwi Bristol Hercules connection rang a personal bell..
( & where the splendid TBO's obtained by proper flight handling/maintenance in NZ, was duly noted)
..as a kid I recall the RNZAF Hercules-powered aircraft flying from the local military aerodrome,
& that they were markedly quieter than the US radial powered aircraft such as the Douglas machines..
The RNZAF used Bristol Hercules powered H-P Hastings' too, & ironically enough,they were replaced by
the Lockheed Hercules as transport aircraft - & yet even more ironically - the RNZAF sent their Hercules..
..powered Bristol Freighters to the ' Nam (to the incredulous amazement of US forces), rather than risk..
.. their expensive new C-130s in dicey supply runs, as the USAF were fairly profligately doing..
..meanwhile.. the USAF were flying Lockheed's next gen Starlifter to Antarctica, transiting via NZ..