Ferrari 308 airboxes… simple right? Sadly no.
Above is the airbox from a European 308. Dry sump, wet sump, early, late… the same airbox from 1976 until the move to fuel injection in 1980. The US cars were however not so consistent…
Firstly, for some reason, perhaps legislative or aesthetic, US cars have quieter airboxes. If you look at the early US airbox above, you will see a thicker neck on the right-hand side. This neck contains additional sound-proofing to effect the quieter airbox. We will call this US airbox type 1. As you can guess, due to our numbering scheme, there’s more than one US airbox…
At the end of 1977 or the beginning of 1978, a change is made to the US airbox. Its neck gets even larger to accommodate an internal flap that is opened and closed by vacuum. The flap was closed after the engine shut down to stop unburnt gasoline from the carburetors venting to the atmosphere. The flap would then open to let ait in again when the engine started. All these mechanics required more space inside the neck of the airbox. Above we can see the flap seems to have been retrofitted to the type 1 airbox. You can see how the new section that contained the flap has been welded on to a type 1 airbox to make a type 2. This modified, welded, type 2 airboxes persisted for several months on the production line.
A few months later in 1978, a third and final airbox design is introduced on US carburetted cars. The functionality is the same: additional sound deadening with a vacuum-powered opening and closing flap, but now the enlarged airbox is fully stamped out and folded instead of having additional sections welded on.
Disclaimer: 308restoration.com describes the restoration work I perform on my car and only my car. I am not a professional mechanic. The website content is presented for entertainment purposes only and should not be seen as any kind of advice, information, instruction or guidance for working on any other car. The opinions stated here are my own and no-one else’s.