Bristol engine test cards.

We were delighted to be given  some 500 1950s works engine testbed cards from the estate of Tony Crook. Thank you to Carole Crook and Anne Marie Cadars for all their help to the Heritage Trust.

Most are of sports or racing engines, some of which  achieved fame or notoriety on the track. These  include Cooper and ERA engines FNS (Frazer Nash Sports) engines followed by Bristol’s own Sports range the BS 1 to 4, and culminating in the 450 engines as used at Le Mans and Rheims. To quote Warwick Banks “Anybody who was anybody in the racing world used the Bristol 2 litre engine in those days”

The later 2.2 engines were also tested on the dynamometer.

The test cards describe fuel mix, air temperature, type of oil, details of  exhaust and ignition, and power output across  the range in the meticulous style so characteristic of the Bristol Aeroplane Company.  Note that compression ratios vary from as low as 8.5 up to 11+. 

At the start of this period these engines were running on low octane fuel. Rationing only ended in 1950  and we had Pool petrol till 1953.  That is why your 2 litre Bristol has an ignition control on the dashboard to prevent pinking on the terrible old fuel of those days.

Simply raising the compression ratio, possible when high octane branded fuels by different manufacturers came out in the early days and competed with each other, would raise the BHP output proportionately. And the very high c/rs mentioned would have been possible for cars running on exotic alcohol based mixes. Nowadays most 2 litre engine are running on much higher c/rs, following years of fuel development and cylinder head planing.

In those days it was common practice to put the engine onto a testbed for tuning and setting of ignition, jetting etc and some engines are mentioned more than once.

If you have one of these Sports racing engines the Heritage Trust can supply a facsimile of your contemporary testbed card. Please contact Andrew Blow for details.

Ray Williams was one of the sports/racing engine line builders and would have worked on some of these engines himself. You will find a video of him talking about those far off glory days attached to this website as part of our video project. View the video.