Demon Fuel Systems 4402020VE - Manual (Page 11)

11
Fuel Pressure
Most gasoline powered race engines usually require between 6 and 7-1/2 PSI fuel pressure. Gasoline
carburetors can be run either at idle or wide open throttle at these pressures. Be sure your fuel
delivery system is properly adjusted and able to maintain volume flow at these pressures. Improperly
adjusted or inadequate fuel delivery will result in poor performance and possible engine damage.
General Tuning and Component Information
Once you have completed the initial installation, and preliminary adjustments, you are now ready to
test the vehicle and evaluate any other possible tuning adjustments. Information on changing the
configuration or fuel metering of your Demon is also included in this section.
Metering Blocks
The metering block is the part of the carburetor having the two-fold job: controlling the flow of fuel into
the venturi and mixing air and fuel prior to its introduction to the main air stream. This is done through
a series of specifically sized orifices located in the metering block. These orifices will be discussed
from a tuning standpoint.
The metering blocks on you Road Demon are Max-Density casting. Each block is specifically tuned
for its specific application. As mentioned before, this tuning is accomplished through the various
sized orifices in the block. Understanding the function of these various devices is critical to
understanding how the carburetor works.
Idle Feed Restrictor
The idle feed restrictor (Fig. 17) controls the amount of fuel that enters the idle circuit from the main
well. This orifice controls the amount of fuel available for the idle circuit. If all other tuning results in a
lean or rich idle circuit, an adjustment here may be necessary. As with any fuel restrictor, the larger
the hole in the restrictor, the more fuel that will be introduced into the idle circuit. Make small
changes, .001" or .002", to all four restrictors and work towards your desired tuning point.
CAUTION: The idle feed restrictors are drilled from the factory. If they are drilled larger, you cannot
go back. Modification is not recommended.
Emulsion Bleeds
There are six (6) emulsion bleeds per metering block, three (3) for each main well (Fig. 17). These
orifices play a part to control the density of the fuel in the block by metering the amount of air that is
introduced into the fuel in the main well. This, in conjunction with the air bleeds in the main body, help
to control the shape of the fuel curve.
CAUTION: Tuning of emulsion bleeds should be performed only by those with a deep knowledge of
carburetors, otherwise, a poor running engine or damaging internal engine parts could
be the result.