That said, the extent of the negative impact varies depending on *which* components are removed and how the engine is tuned (or not tuned) afterwards. Removing some components will have a more pronounced effect than others.
Here's a breakdown:
Components that removing will likely cause significant problems:
* EGR (Exhaust Gas Recirculation) System: This is a major player in emissions control and its removal will drastically alter combustion parameters. It'll likely cause detonation (pinging) under load, potentially damaging the engine, and significantly reduce fuel economy.
* Catalytic Converter: While its removal might seem to give a slight power bump (mostly due to reduced exhaust backpressure), it's illegal in most places and will cause significantly higher emissions, leading to potential fines. It's also likely to create a richer mixture causing fouling of plugs, sensors and increased fuel consumption.
* Air Injection System (AIR): This pumps air into the exhaust manifolds to help burn off unspent fuel. Removal will likely increase emissions and potentially reduce performance under certain conditions.
* Thermostatic Air Cleaner: Removing this part often results in cold air being sent into the engine, which negatively affects fuel mixture and performance.
Components whose removal might have a less noticeable (but still present) effect:
* Vacuum advance on distributor: If you remove or disable the vacuum advance portion of your distributor's timing mechanism, the engine's timing will be static, probably resulting in slightly reduced efficiency and power throughout the engine's rev range.
Important Considerations:
* Legality: Removing emission control devices is illegal in most jurisdictions.
* Engine Tuning: Even if a component is removed, without proper engine tuning (recalibration of the carburetor or fuel injection system), you'll likely see poor performance and other problems. A proper tune is necessary to compensate for the changes in air-fuel ratio and engine timing.
In short, there's no safe way to remove emission controls from a 1977 305 and expect *no* negative effects on performance. Any gains will likely be marginal and overshadowed by the risks of damage to the engine, poor fuel economy, and legal consequences. If you're looking for performance upgrades, focus on modifications that enhance the engine's capabilities *within* the existing emission system (e.g., intake, exhaust, camshaft, carburetor upgrades - but even these need careful consideration and potentially professional tuning).
