Intake and Exhaust:
* Performance Intake Manifold: A high-rise or aftermarket intake manifold improves airflow into the cylinders, leading to better breathing and increased power. Edelbrock Performer RPM and other similar intakes are popular choices.
* Headers: Replacing the restrictive factory exhaust manifolds with headers significantly improves exhaust flow. This allows the engine to breathe more freely and produces a noticeable power gain. Long-tube headers offer the best performance, but may require modifications to the exhaust system and potentially the steering linkage. Shorty headers are a less invasive option.
* Exhaust System: After installing headers, a free-flowing exhaust system (with a suitable muffler for your desired sound level) will maximize the benefits of the headers. A cat-back system is a common choice.
Fuel System:
* Performance Carburetor (if applicable): For carbureted 305s, a larger or more efficient carburetor will provide better fuel delivery. Holley and Edelbrock carburetors are popular options. Proper carburetor tuning is crucial for optimal performance and fuel economy.
* Fuel Injection Upgrade (if applicable): For TBI or throttle-body injected 305s, upgrades such as a larger throttle body or a performance fuel pressure regulator can improve airflow and fuel delivery. A full aftermarket fuel injection system is also possible, but more complex and expensive.
Ignition System:
* Performance Ignition Coil: A higher-output coil provides a stronger spark, leading to better combustion.
* Ignition Wires: High-performance ignition wires reduce resistance and improve spark delivery.
* Electronic Ignition System: Upgrading to an electronic ignition system (if not already equipped) will provide a more consistent spark than a points-based system.
Internal Engine Modifications (More Involved & Costly):
* Cam Shaft Upgrade: A performance camshaft with more aggressive lift and duration will increase power but can also affect low-end torque and idle quality. Choosing the right cam is critical.
* Valvetrain Upgrades: Upgrading to roller rockers, stronger valve springs, and better pushrods can improve valve train efficiency and allow the engine to rev higher.
* Porting and Polishing: Porting and polishing the cylinder heads will smooth out the air flow pathways, improving breathing efficiency. This is generally a professional job.
* Pistons and Connecting Rods: For a significant power increase, upgraded pistons and connecting rods may be necessary, but this is a major undertaking requiring professional machine work.
Important Considerations:
* Budget: Modifications range from relatively inexpensive (exhaust, air filter) to very expensive (internal engine work).
* Goals: Are you looking for more horsepower, better torque, or a specific sound? This will influence your choices.
* Driving Style: A more aggressive camshaft might be great for racing but less enjoyable for daily driving.
* Professional Installation: Some modifications are best left to professionals, especially those involving engine disassembly or machine work.
The Chevy 305 is not a naturally high-performance engine, so expect modest gains relative to the investment, especially compared to modifications on a larger displacement engine like the 350. Focusing on intake, exhaust, and ignition improvements usually yields the best bang for the buck. Consider your budget and goals before undertaking any modifications.
