Bentley Is Recreating It’s Historic 4-1/2 Litre Blower Engine

When you think of incredible engine performance, Bentley probably isn’t high up on that list. While Bentleys are known for their sheer opulence, and certainly don’t lack horsepower, they aren’t known for their racing prowess these days. However, that hasn’t always been the case, as prior to World War II, Bentley had quite the racing pedigree.

One of the more notable performance vehicles was named after the engine which powered it — the 4-1/2 Litre Supercharged, or the “Blower Bentley.” While not particularly powerful by today’s standards – making between 175 and 242 horsepower — that was between a 65 and 112 horsepower (59- to 86-percent) improvement over the naturally aspirated versions of the engine, and a lot of power in the 1920s.

The inline-four-cylinder engine measured 4,398cc (or 268.4ci) thanks to a 100mm (3.900 inches) bore and 140mm (5.500 inches) stroke. It was a single overhead camshaft arrangement with four valves per cylinder, dual spark plugs, and was fitted with an enormous (for the time) Roots supercharger, topped with a pair of carburetors to feed the combination, which consumed four liters of fuel per minute at full song.

Unlike modern engines, the Roots blower doesn't sit on top of the engine, but rather directly in front of the engine, driven directly off of the crankshaft.

So what does all that have to do with the Bentley of today? Well, Bentley understands the importance of its history, so much so, that they will be recreating a dozen of those powerplants from 1928 in order to power Bentley’s “Continuation Series” specialty run of vehicles. Like the originals, they will feature an aluminum crankcase, with cast iron cylinder liners and a non-removable cast-iron cylinder head.

Additionally, the superchargers will be exact replicas of the Amherst-Villiers Mk IV roots-type supercharger that were originally equipped on the Blower Bentleys. While benefitting from modern metallurgy, all the rest of the details will be period correct. Testing of the initial engine was performed at Bentley’s Crewe headquarters in a test facility that originally performed run-in and power testing of Merlin V12 engines in 1938, originally powering Spitfire and Hurricane fighter planes of WWII.

Once all of the modern testbed calibration and durability testing is complete, then the modern 4-1/2 Litre Blower engine will undergo real-world testing. Once complete, twelve of the engines will be produced to power the dozen vehicles planned of the Blower Continuation Series.

Calibrated in test cells originally used for V12 Merlin engines in World War II, the new engines have the benefit of modern calibration electronics and metallurgy. Other than that, they are true to the original design from 1928.

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About the author

Greg Acosta

Greg has spent fifteen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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