A rich running carburetor is a common problem for engines equipped with Rochester B, BC, or BV carburetors. Below you’ll find a list of symptoms to look for, common causes of a rich carb, and how to fix it.

SYMPTOMS

• Black smoke from the exhaust: Excess fuel burns incompletely, leading to black soot accumulation.
• Poor gas mileage: The engine is using more fuel than necessary.
• Hesitation and bogging: The engine struggles to accelerate smoothly due to the incorrect air-fuel mixture.
• Strong fuel odor: Unburned fuel escapes the exhaust, creating a noticeable gasoline smell.

POSSIBLE CAUSES

Fuel Level Issues:

• Sticking Float: A faulty float can cause the fuel level in the carburetor bowl to be too high. This allows too much fuel to enter the engine, resulting in a rich mixture.

• Worn Needle Valve: The needle valve regulates fuel flow into the carburetor bowl. Wear or damage can prevent it from properly shutting off flow, leading to an overflow.
• Float level is off: Check the float level. The level is different for most vehicles. Find the actual measurement here

Internal Passages:

• Clogged Passages: Dirt and debris can accumulate in the carburetor's internal passages, disrupting the air-fuel metering. This can lead to a rich mixture if the fuel passages are less restricted than the air passages.

• Power Valve Issues: The power valve regulates additional fuel flow during acceleration. A malfunctioning power valve can stay open, allowing too much fuel into the engine. We see frozen power valves often. **Use heat to loosen the power valve.** Find everything you need to know about the **power circuit here.**

  

External Adjustments:

• Incorrect Idle Mixture Setting: The idle mixture screw controls the amount of air entering the engine at idle. An improperly adjusted screw can cause a rich mixture.
• Vacuum Leaks: Leaks in hoses connected to the carburetor can introduce unmetered air, causing the engine to compensate with more fuel (rich condition) to maintain idle speed.

Main Jet:

• Before replacing your jet you should think through as to why.