As you can see in the pictures below circled in red there are pipes that are right next to the carburetors on this Abarth Tipo 240 v12 engine and Ferrari Lampredi inline 4 dohc engines (on the Ferrari engine they are going directly on top of the cylinder heads right between the 2 camshafts and aren't next to the carbs). What are they? As a side note for if anybody says they are the exhaust manifolds no they aren't. They are something else and I want to know what they are. Is it something related to coolant? In the Ferrari engine in the last picture they are connected to a pipe that goes towards the front of engine bay towards the radiators.
Those are the cooling pipes to control the engine temperature.
The water input to the block is seen in the lowest picture under the right hand end of your red loop.
Looking at the middle picture it is evident that there is no other pipe connection to the top of the cylinder heads for the coolant.