At the start of the 1930s, Penta produced more Volvo engines than Penta engines each year, and Volvo’s financial interest in Pentaverken increased. The production of marine, industrial and car engines under one roof was no longer as smooth an operation as it had been in the beginning. Although time and motion studies and assembly-line production were introduced at an early stage – as early as 1930 – there were constant problems in the spring and summer, which was the high season for Volvo and other customers. Volvo was a demanding customer whose favors were being sought by many other Swedish companies and it was often necessary to work around the clock to complete orders.
Volvo business became increasingly more important for Penta and, in 1935 Volvo bought its engine supplier and renamed the company Volvo Pentaverken. In the same year Volvo moved a design and sales department for non-automotive engines to Gothenburg and set up AB Pentaverken in Gothenburg, the company from which AB Volvo Penta grew. The same year, the Hesselman engine was introduced: a six-cylinder crude-oil engine with three-cylinder idling, a very advanced design for its time. During this time, women were employed at the company for the first time.