An engine designed and manufactured by Fabrica Automobili Isotta-Fraschini in Milan and under licence by Bianchi. It was equipped with two Zenith-type carburettors and a decompressor to facilitate engine starting. In the presented version, forced lubrication was provided by an oil pump.
The Isotta-Fraschini V.4b engine was used in Macchi M.5 flying boats and in the three-engined Caproni Ca.30 and Ca.36 heavy bombers.
| Configuration | 6-cylinder inline |
| Cooling | water |
| Compression ratio | 5.0 |
| Displacement | 14.3 l |
| Weight | 275 kg |
| Maximum power | 170 hp at 1,450 rpm |
