Aircraft engine!?! Thanks for the pointer. I also found a story in Horseless Carriage Gazette, March-April 1966:
http://www.ddvvmc.com.au/librarydocs/HorselessCarriage_vol28no2.pdf
This giant car, formerly mistaken for one of Count Zobrowski's famous "Chitty-Chitty-Bang-Bangs," was constructed in England for E. T. Scarisbrick by C. H. Crowe & Company of London in 1921. The six cylinder Benz engine from a captured German airplane of the first world war has a bore of 140 mm. and a stroke of 196 mm.; a displacement of 18.8 liters. The chassis, chain-driven and geared 1 V3 to 1 on top gear, is Mercedes-built of approximately 1910 and obviously designed for a heavy touring car of that period. The total weight of the car today is 4,000 lbs. Though the car was built for competition at the Brooklands motordrome in Surrey, England during the post-WW I era of such aero-engined specials, the only positive evidence of its racing achievements is that of winner in speed trials at Fanoe Beach, Denmark in 1923. Driven then by owner Scarsisbrick, the car was known as "Rabbit-the-First." The car was subsequently owned by coachbuilder Marbury of London and probably others, and by 1930 its brief racing career and identity appear to have been forgotten.
For in 1930 it was bought sight unseen by Alistair Bradley Martin of Long Island, New York, having been represented as one of the Maybach aero-engined Chittys." Originally equipped with a standard Mercedes radiator of the 1910 period, before it arrived in the US this had been replaced by an ill-fitting one from a Speed-Six Bentley. The car required extensive general restoration, work then undertaken by John Oliveau and associates. After completion it appeared in the VMCCA Easter Parade in New York in 1940, now sporting a Locomobile radiator of 1919 vintage closely resembling Mercedes design. Shortly after, erroneous reports being circulated identified the car as a Zborowski "Chitty' and considerable controversy resulted. Claims both pro and con appeared in the motor journals here and abroad. The confusion is understandable. The cars were identical in appearance and both the Maybach and Benz firms produced aero engines from identical designs. But after painstaking investigation of all the factors for and against, Walter C. Hadley of West Redding, Connecticut, definitely established the cars non-relationship to the Zborowski specials. The present owners, Peter Helck and Charles Lytle, first heard of the existence of the pseudo- "Chitty" in 1950 from VMCCA member Leo Peters of Smithtown, Long Island. It was then owned by the Ellis brothers of Sea Cliff, Long Island, and again showed signs of marked deterioration. Both Henry Austin Clark Jr. and the late James Melton graciously withdrew their own acquisitive interests in favor of the present owners, after which Leo Peters got it in running shape and attested to its vast power in first, second and third gear. Perhaps reluctance or lack of road prevented use of top gear! In its new quarters the car then stood on blocks for fifteen years. In December 1963 Arthur Jim Hoe, Duesenberg specialist, was given the job of restoring it completely, all body repairs to be done by Gus Reuter. To these experts in the art of recreating fine automobiles go the credit for bringing back into mint condition this excellent example of the aeroengined specials of the 1920's period.