The rotary vane intake manifolds of Polini and Malossi allow the use of larger carburettor diameters. The PHB series from DellOrto, for example, is suitable for this purpose and is available in 28 and 30mm intake sizes. For assembly the original carburettor sump and the original carburettor are completely removed and replaced by the Polini or Malossi intake manifold. For engines with separate lubrication the automatic oil supply of the engine is not necessary. Here you have to change to mixture lubrication (e.g. 1:50). The pole piece is cheaper than the Malossi one, but does not cover the bore in the engine housing for the oil pump shaft at the same time. If the pole piece is used on a separate lubrication motor, the hole in the oil pump shaft must be closed with a suitable plug (daring natures use a champagne cork cut to size). Both intake ports have a cross-section of 28mm. If larger carburettors are to be used sensibly, the sockets must be ground to the dimension of the carburettor diameter (fan grinder attachment for the drill). More than 30mm cannot be used on the rotary vane motor without major modifications. The greatly extended intake path of the intake manifold leads to an increased torque on most engines, at a lower speed level in direct comparison to the original carburettor. This makes these intake manifolds especially interesting for touring engines (e.g. with a Pinasco cylinder). With the longer intake path, it is also excellent for compensating too long intake timing (e.g. the long stroke shaft). This effectively dampens the blowback, i.e. the blowing out of fuel from the carburettor. In addition, the long intake manifolds are ideal for mounting a Boost Bottle. This also makes it easier to tune problem engines.
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