This line of 2.5 engines were produced in the '50s by the now dismantled Barbini factory and were of the following specifications:

The Red Head in the picture (note the needle bearing cage) was raced in 1958 by the Cantelli-Amerio team over the Italian championship with excellent results. History does not say (or does not like to remember...) how excellent those results were, but I understand they did not win the championship!

(Information given by Mario A. Ferrero)