1. CARBURETOR CIRCUITS AND COMPONENTS
CBC AUTOMOTIVE TECHNOLOGY

2. BASIC CARB DESIGN Conventional Design
Computer Control for Better Fuel Metering
1,2,3,4 barrel carbs

3. CARBURETOR SYSTEMS FLOAT SYSTEMS Pg 7 Float Material Maintains Level
Float setting
Viton Needle and Seat
Dampening Spring
Float Bowl Construction
Float Drop

4. FLOAT BOWL VENT Vented to outside atmosphere Vapor Seperator
Mechanical Vent
Dirty air filters affect pressure in bowl
Usually located near center of bowl

5. IDLE SYSTEM Not enough airflow at idle to allow main system to operate
Pg 8
IDLE SYSTEM
Not enough airflow at idle to allow main system to operate
Manifold vacuum is high to draw fuel out idle ports
Usually adjustable
Idle air bleed helps atomize fuel and prevents siphoning

6. TRANSFER CIRCUIT Transfers fuel off in Off idle mode
Pg 8
TRANSFER CIRCUIT
Transfers fuel off in Off idle mode
Adds fuel to mixture as throttle plate opens to cover “sag”

7. MAIN SYSTEM Fuel supplied by “main jets”
Operates under high venturi vacuum
Atmospheric Pressure pushes fuel out discharge nozzel

8. ACCELERATOR PUMP SYSTEM

9. HOT IDLE COMPENSATOR
Allows mixture to be lean out during hot idle conditions caused by excessive fuel vapor

10. CHOKE TYPES Automatic Chokes Integeral Choke Divorced Choke
Manual Hot Air
Electric
Integeral Choke
Divorced Choke

11. CHOKE SYSTEM Operates when cold and low rpm
Pg 10
CHOKE SYSTEM
Operates when cold and low rpm
Sometimes fuel extracted from air bleed holes
Allows 5:1 mixture
Vacuum Break or Choke Pull Off

12. CHOKE SYSTEM

13. CHOKE COIL OPERATION

14. CHOKE PULLOFF Forces the choke open slightly just after engine starts.
Position determined by
torque of coil
air velocity on blade
vacuum on piston
must adjust correctly!

15. POWER CIRCUITS Mechanical Power Valve Adjustable
Sometimes combination with metering rods
Flows through a circuit into main metering system

16. VACUUM POWER VALVE Different locations on carbs. Usually in bowl area.
Pg 8
VACUUM POWER VALVE
Different locations on carbs. Usually in bowl area.
Supplies Extra fuel under heavy loads
Operated by Manifold Vacuum

17. BAROMETRIC PRESSURE COMPENSATOR
Compensates for altitude
Fairly troublefree

18. THROTTLE POSITION SENSOR

19. IDLE SPEED CONTROL

20. A/C IDLE SOLENOID Used with A/C
Compensates for drag on engine caused by Compressor
Adjustment is usually seperate from Curb Idle rpm.

21. TYPES OF CARBURETORS

22. TERMINOLOGY Emulsion Float Circuit Lean Metering Metering Rod
Power Valve
Rich
Stoichiometric ratio
Throttle Kicker
Throttle stop solenoid
Transfer slot
Vaporization
variable venturi
Venturi
Air Bleed