All Road Demon carburetors have three
vacuum sources on the baseplate that can be
used for PCV, distributor vacuum, diagnostics,
or any other vacuum operated accessories. The
large fitting on the back of the baseplate, and
the second fitting of the two small fittings on
the side of the baseplate, are direct (below the
butterfly) manifold vacuum sources. The front
small fitting on the side of the baseplate,
opposite the throttle linkage plate, provides a
ported (above the butterfly) vacuum source. Be
sure all vacuum lines are connected or plugged
before you attempt to start the engine.


The port at the rear of the baseplate is intended for a secondary manifold vac source as in PCV and brakes. However, I would not recommend running brakes and PCV off of the same port. Find a direct manifold port for the brakes if you can.

The smaller ports on the side are for ported and direct vac sources. The port in the front is ported for time advance with throttle application and the rear is primarily used for diagnostics, accessories, and distributors that require full time vacuum advance.


If you experience heating up issues at idle, then you may need to run the full time advance on the distributor.