Manufactured in Helsingør (in English, Elsinore), Denmark, by Thorning Bensen, the Thorning 3.5 cc diesel was introduced in late 1950 to meet the competition from rival Danish manufacturer CEROS, who released a very similar 3.5 cc model at more or less the same time. The design of both engines was clearly based upon that of the light and compact AMCO 3.5 PB model from England, which was one of the most successful 3.5 cc diesels at the time. 

A crankshaft front rotary valve 2.5 cc FRV model was also released soon thereafter. Unfortunately, Bensen made a serious design error with this model by omitting a bushing from the main bearing. In doing this, he was emulating a number of succesful English designs. However, those English models used a relatively hard-wearing die-casting alloy, whereas the Thorning crankcases were gravity-cast in plain aluminium. As a result, they wore prematurely, even during the break-in process. Word of this soon got around, leading to a high level of sales resistance.

Bensen moved quickly to address this problem by adding a bushing to the main bearings of his 2.5 cc model - the 3.5 cc design had featured such a bearing from the outset. However, the damage to the  reputation of the Thorning range had been done. Although it was actually a very useful engine having a performance which was comparable to that of the very successful AMCO 3.5 PB,  the 3.5 cc Thorning did not achieve much sales success. Thorning Bensen left the model engine manufacturing business in late 1951 after producing fewer than 500 examples of this excellent motor.

A full review of the Thorning 3.5 cc model, including a bench test, appears elsewhere on this website.