INTRODUCTION
The Holley Carburetor Model 1904 is a notable advance in carburetion engineering. It combines the time-proved
Holley characteristics of efficiency, dependability, and effective performance in a compact unit of outstanding
simplicity.
The elimination of the conventional air horn has resulted in a carburetor less than two thirds the height, but having
a capacity comparable to units of standard design. By locating the choke plate in the venturi, the elimination of the
air horn has been accomplished with no loss in efficiency or performance. In addition, the arrangement of the
mixture discharging components in relation to the choke plate when open, aids in the distribution and vaporization
of the fuel discharged into the airstream passing through the venturi.
In line with the advanced engineering conception of this carburetor is the transparent fuel bowl of most versions
of this carburetor model. This transparent fuel bowl greatly simplifies trouble shooting and carburetor servicing.
Overhaul procedure also has been simplified by combining most of the fuel metering elements of the carburetor
in a single, easily replaceable assembly.
Close attention to design details has resulted in the improvement of various other parts. A spring
arrangement is incorporated in the fuel inlet needle to cushion float movement and act as a vibration dampener to
stabilize the fuel level on rough roads. The conventional economizer piston and accelerating pump piston have
been replaced by neoprene diaphragms to insure more positive action and increased service life.
This manual includes a full factory-approved overhaul procedure together with much valuable information
on the description, operation, and adjustment of the Carburetor Model 1904. Careful adherence to the procedures
given in overhauling this carburetor will insure the retention of the high standard of economical, efficient, and
dependable performance, characteristic of all Holley products, which is delivered by this carburetor.
DESCRIPTION
HOLLEY CARBURETOR MODEL
1904 STANDARD ENGINE
1. DESIGN
The Holley Carburetor Model 1904 is a single-barrel
downdraft unit of advanced design. This carburetor is
a model of noteworthy compactness and simplicity
with its many new features assur
ing lasting, effective, and dependable service.
Most versions of this carburetor model contain a
tempered glass fuel bowl which permits visual inspection
of the float chamber. The action of the float and of the
economizer stem during operation can be readily
observed. Fuel level is clearly visible and the presence of
water or sediment in the float chamber is readily
detected.
Fuel from the carburetor fuel inlet discharges below the
fuel level in the float chamber to prevent foaming or
splashing, assuring a constant, uninterrupted fuel flow to
the metering components of the carburetor. Fuel in the
float chamber circulates completely around the easily
removable main well and economizer body which
contains most of the fuel metering elements and passages.
This circulation has a cooling effect on the fuel being
metered through the passages in the main well and
economizer body. In addition to that factor, the high-lift
design of the carburetor main well gives this carburetor
excellent hot operation and anti-percolation qualities.
Improved control of the power enrichment
