Carburetor Conversion for Camaro/Firebird

Embarking on the journey of converting your Camaro or Firebird from Electronic Fuel Injection (EFI) to a carburettor setup is a significant undertaking, often driven by a desire for simpler maintenance, a more mechanical feel, or pure, unadulterated power. While EFI systems offer precise fuel delivery, a well-tuned carburettor can provide a visceral driving experience. This guide will walk you through the process, detailing the necessary parts, the crucial steps involved in routing fuel, and essential considerations for a successful swap.

Essential Parts for the Conversion

Before you begin, ensure you have all the required components. Gathering these beforehand will save you time and frustration during the conversion. Here's a comprehensive list:

Step-by-Step Conversion Process

1. Removing the EFI System

Begin by carefully dismantling the EFI components from the intake manifold upwards. For TBI (Throttle Body Injection) systems, this is relatively straightforward. TPI (Tuned Port Injection) systems are more complex and will require more time. Once removed, thoroughly clean the gasket surfaces on the cylinder heads and the lifter valley edges. Use rags to stuff the ports and lifter valley to prevent any debris from entering the engine – this is a critical step to avoid internal damage.

2. Installing the Carb Intake Manifold

The choice of intake manifold is often a matter of personal preference and intended use. Dual-plane manifolds, such as the Edelbrock Performer or Performer RPM, are generally favoured for their broad powerband and street drivability. If you're using an aftermarket manifold designed for earlier heads (pre-87) on later model heads (87-up), you may need to slightly elongate the four middle bolt holes on the manifold to align correctly. This can be achieved with a Dremel or die grinder, offering a cost-effective solution compared to purchasing a specific 87-up manifold.

3. Installing the Distributor

The new distributor needs to be non-computer controlled. You have a few options: sourcing one from a junkyard, purchasing a remanufactured unit, or opting for an aftermarket performance distributor. GM used suitable distributors from approximately 1974 to 1983. Ensure the distributor is complete with its ignition module, wiring harness, cap, rotor, and coil. When installing, align it with the same tooth as the original distributor. The ignition coil will have two wires; connect these to the new coil's BATT (usually red/pink wire) and TACH terminals. If you can't find the correct plug assembly, crimp-on female spade connectors will suffice. Finally, connect all spark plug wires, ensuring they are in the correct order and on the right terminals.

4. Mounting the Carburettor and Linkage

With the manifold in place, install the carburettor using a new gasket. Tighten the bolts to the manufacturer's specified torque. It's essential to install a throttle return spring. A convenient location is often under one of the rear carburettor mounting bolts to ensure consistent tension on the throttle linkage. Fabricating or adapting the throttle and TV (throttle valve) cable linkage will likely be necessary. For TBI models, small pieces of sheetmetal, drilled with holes at each end, can be used to connect the cables to the carburettor's throttle arm. The TV cable typically snaps onto a bolt head, while the throttle cable has a pre-drilled hole.

5. Connecting Vacuum Lines

Proper vacuum line routing is crucial for drivability and preventing vacuum leaks, which carburettors are particularly sensitive to. Connect the vacuum advance line from the distributor to the appropriate timed vacuum port on the carburettor. Consult your carburettor's manual for the correct port. Do not forget to connect the vacuum line for your power brakes. You might need to repurpose a port on the carburettor or manifold, or use a vacuum block. Ensure all other vacuum ports on the carburettor and manifold are either connected to their intended components or securely plugged. Double-check every connection for leaks.

6. Routing Fuel to the Carburettor

This is arguably the most critical part of the conversion, as carburettors require a specific fuel pressure range, typically 5-8 psi. There are two primary methods to achieve this:

Option A: Using an AFPR (Adjustable Fuel Pressure Regulator)

This is generally the simpler method. You'll install a 3-port, return-style AFPR inline with your existing fuel lines. Locate the three lines coming from the fuel tank on the driver's side: fuel delivery, fuel return, and the charcoal canister vent. The fuel delivery line is usually slightly thicker. Purchase 3/8" pipe thread to 3/8" hose nipple fittings with thread sealant. Connect one fitting to the 'in' port of the AFPR, another to the 'return' port, and the third to the 'pressure' or 'out' port. Route a hose from the car's fuel delivery line to the AFPR's 'in' port. Connect the fuel return line to the AFPR's 'return' port. Run a new fuel line from the AFPR's 'out' port to the carburettor's fuel inlet. For the charcoal canister line, disconnect it from the canister, clamp a length of 3/8" hose onto the hard line, and route it to a safe location outside the engine bay to vent fuel tank pressure. Removing the charcoal canister entirely is also an option.

Option B: Installing a Carb Fuel Pump

This method involves dropping the fuel tank. You'll need to replace the in-tank EFI pump with a carburettor-specific pickup or a length of suitable hose. For the external pump, high-volume electric units like the Holley Red or Blue are excellent choices. Install the pump according to the manufacturer's instructions, ensuring it's plumbed correctly to deliver fuel at the required 5-8 psi. This setup might offer better long-term reliability and capacity for future engine upgrades.

7. Addressing Other Considerations

• Check Engine Light: With the EFI system removed, the Engine Control Unit (ECU) will no longer manage anything, causing the Check Engine light (SES light) to illuminate and remain on. You can either ignore it or remove the bulb from the instrument cluster.
• Torque Converter Lock-up: If your vehicle has an automatic transmission, the computer will no longer control the torque converter lock-up. This typically results in a slight reduction in fuel economy during highway cruising (above 35 mph in 4th gear). You can live with this, install a manual lock-up switch, or purchase a dedicated kit to retain this functionality.

The Moment of Truth

Once all connections are made and secured, perform a thorough double-check of all fuel, vacuum, and electrical connections. Ensure there are no fuel leaks. When you're confident, crank the engine. If everything has been done correctly, it should fire up and run. The immediate next steps involve setting your ignition timing and then tuning the carburettor for optimal performance, which are subjects for separate, detailed guides.

Finally, the ultimate ritual: locate your ECU under the passenger side dash, remove it, and celebrate your successful conversion to a more raw and powerful driving experience. You have now embraced the world of mechanical simplicity and brute force!

Frequently Asked Questions (FAQ)

Q: Will my Check Engine light stay on after the conversion?
A: Yes, as the ECU is no longer controlling any engine functions, the Check Engine light will remain illuminated. You can safely ignore it or remove the bulb.

Q: How will this affect my fuel economy?
A: You may notice a slight decrease in fuel economy, particularly on the highway, because the torque converter lock-up feature controlled by the ECU will no longer function.

Q: What is the correct fuel pressure for a carburettor?
A: Most carburettors require a fuel pressure between 5 and 8 psi.

Q: Can I use an older intake manifold on newer heads?
A: Yes, but you may need to slightly elongate the four middle bolt holes on the manifold to ensure proper alignment with the bolt holes on 87-up cylinder heads.

Q: Is it difficult to fabricate the throttle linkage?
A: It can require some trial and error, especially with different carburettor and throttle body setups, but it's generally manageable with basic fabrication skills and parts.