Gray Marine 1944 BB Updraft Carburetor

1944 Gray Marine BB Updraft Carburetor – Carburetor number 586S. Correct for 4 cylinder engine, model 4-52. 3 7/16″ bore, 4 3/8″ stroke.

Carburetor kit for this BB updraft carburetor

Flange size, 1 1/2″, 2 11/16 mounting bolt OC.
Throttle bore, 1 1/2″
Main venturi, 15/16″ I.D.
Air bleed through venturi, to idle passage .0669″ diameter drill.

Float Setting
Top of float 1/32 – 1/16″ below top of surface of lower body

Balance Vent Tube
Inside diameter, 7/32″

Gasoline Intake Needle
Triangular, horizontal. No 44 (.086″) drill in needle seat

Idle Jet Tube
Jet size, .0236″ (60mm) drill

Idle Ports
Lower port size .062″ to 064″ diameter. Top of port located .005″ to
.009″ below lower edge of valve. Upper port size .053″ to .057″
diameter (for idle adjustment screw)

Set Idle Adjustment Screw
1/4 to 1 turn open. For richer mixture, turn screw out. Do not idle
engine below 300 rpm or 6 mph

Vacuum Spark Port
No. 69 (.029″) diameter

Main Metering Screw
Adjustable 1-2 turns

No 33 (.113″) drill, I.D.

Accelerator Jets
2 No 62 (.038″) drill 1/16″ from shoulder
2 No 62 (.038″) drill 3/8″ from shoulder
2 No 62 (.038″) drill 23/32″ from shoulder
2 No 62 (.038″) drill 1 1/16″ from shoulder

Air Bleed to Nozzle
Vent tube size .048″ drill

Step Up Jet
Power orifice size .0315″ (80mm) drill

Accelerating Pump
Type, low pressure, delayed action. Stroke Summer setting, inner hole, short stroke 9/16″. Winter setting, outer hole, long stroke, 1″. Pump intake ball check size 1/8″. Pump discharge retainer (in pump valve age assembly) No 52 (.0635″) diameter drill size.

Manual butterfly type, with pressure relief poppet valve. Lever on left side.


Recent Posts

Choke Types

We have 4 different types of chokes, Intregal, Divorced, Electric & Electric Conversion.

Intregal Choke

Integral ChokeThe integral choke is mounted on the carburetor, either near the top, or near the bottom. The illustration shows the choke mounted on the top of the carburetor. The thermostat is heated by a heat tube that runs down to the exhaust manifold. The heat tubes heats up the thermostat and moves the choke valve to the open position. A vacuum passage in the carburetor feeds up to the choke housing and helps pull in the heat from the heat tube. Some of these chokes will also have a hot water jacket running through, or on the thermostat to facilitate heating.

Divorced Choke

Divorced ChokeThe divorced choke typs has the thermostat mounted in the intake manifold instead of on the carburetor. In this illustration, the arrow points to the thermostat which is covered by a metal shield. A rod connects the thermostat to the choke lever, which controls the choke valve to be opened, or closed. As the intake manifold heats up, the thermostat mounted, expands, opening the choke valve.


Electric Choke


Electric ChokeThis is a typical electric choke mounted on the carburetor, which is integral. In this case there is one wire on the choke thermostat. This is the 12v source, which all electric chokes use. The thermostat is grounded via the carburetor itself. Some electric chokes will have a 2nd wire (ground wire), which is connected back to the carburetor. When the key is on the thermostat is heated up, opening the choke valve.

Electric Choke Conversion


Electric Choke ConversionThis is a typical electric choke conversion kit. This is used to convert an integral, or a divorced choke to an electric choke. These choke kits come with a temperature sensor that bolts on to the intake manifold, which provides more accurate choke control than with an electric choke without the gauge. The electric choke conversion kit is not used for a manual choke conversion. The choke housing must be in place in order for it to work.
This choke installs in 20 minutes or less with no special
tools. Remove the old choke thermostat and replace with this choke conversion kit.
Attach the temperature sensor under an existing engine bolt.
Wire the positive wire into the vehicles electrical system. Ground the choke to the carburetor.
Complete instructions are provided for each application.


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