Built from 1946-1947, the J1 was released as a two-seater competition car together with the K1 touring two-seater and the L- Type touring 4-seater. The J1 was a starkly trimmed and equipped 2-seater competition car on a 100 in (2,500 mm) wheelbase. Powered by a 140 hp (100 kW; 140 PS) 3,917 cc (239.0 cu in) overhead valve Mercury V8, the J1 had a top speed of 85 mph (137 km/h), limited by the low rear axle gearing. Only 12 were produced and went only to buyers who would rally them. They had good ground clearance and the front wings were removable. Copies driven by Allard himself, Maurice Wick, and others, and was a successful racer. Imhof won the 1947 Lisbon Rally in a J1 powered by a Marshall-supercharged version, while Leonard Potter took the Coupe des Alpes that year.