It was not only with Rolls-Royce cars that General Motors’ Cadillac division were notably co-operative (July MOTOR SPORT). From the invaluable R-R EC Heritage Trust Archives I have now learned that when Derby was well into the production of its ‘silent sportscar’ Cadillac’s chief engineer, E W Seaholm, gave R-R much technical assistance. This included the dispatch to R-R’s Mr Grylls (who was to be responsible for the advanced R-R Silver Shadow) of GM’s data on how to make crankshaft balancers. At that time, the era of the pre-war 3 1/2 and 4 1/4-litre Bentleys, Derby was testing V8 and V12 Cadillacs and duly analysing their components.
In 1938 Mr Grylls asked Seaholm about the ‘flexible flywheel’ on the Model 60 Caddy, and Robotham responded with details of the R-R damper, used even with a seven-bearing crankshaft. R-R compared their 4s4 Bentley and the 1936 V8 Cadillac. Lord Hives of RollsRoyce was concerned that their premier British sportscar was being “trimmed up” on performance by a £400 American saloon. They took reassurance that the Bentley was geared to do 96mph, with good economy, to the Caddy’s 90mph, and if a driver wanted performance he could use the gearbox.
But the American car’s lower gearing and 5.6-litre engine did give five per cent better top-gear acceleration. It weighed 3Scwt, the Bentley 33cwt, so its theoretical gain was greater still. Unless the 41/4’s engine was the more efficient, the top gear pick-up of the Caddy would beat the Bentley’s third gear acceleration.
It was found that despite its larger engine the American car was only two per cent heavier than the Bentley; Hives and Robotham had saved weight by not having hydraulic jacks or 3in wider bodywork. The R-R engineers were duly warned that soon heavier bodies would be demanded by customers and so they should ‘make hay while the sun shines’ and be aware that by then the Cadillac and Buick Century would have increased performance. But when Rolls-Royce sent a V16 Cadillac to Hooper’s this coachbuilder was not impressed, its body heavier, albeit stiffer, than theirs, with external door hinges, ‘Christmas tree’ treatment of many of the minor fittings, general untidiness all round, and ‘great cast-flanges on the hub-caps’. No wonder so many Rolls-Royces ended up being bodied by Hooper.