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

Sizes
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

Nozzle
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.

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