1. Internal Engine Components:
* Larger Displacement: While you're starting with a 350, you could increase displacement by stroking the crank (longer stroke) or boring the cylinders (larger bore). This is a more involved process requiring machining and potentially new pistons and connecting rods. A 383 stroker is a popular and relatively easily achievable option, providing a solid horsepower increase base.
* Forged Internals: Stock internals are typically not strong enough to handle the increased power and stress of a 400hp build. You'll need forged pistons, connecting rods, and a forged crankshaft to withstand the higher cylinder pressures and RPM.
* High-Performance Camshaft: A camshaft tailored to your intended RPM range and power band is critical. A larger camshaft with more aggressive lift and duration will improve airflow, boosting horsepower.
* High-Flow Cylinder Heads: Factory heads are restrictive. You'll need aftermarket cylinder heads (e.g., AFR, Edelbrock, Dart) with larger valves, better porting, and improved flow characteristics. Porting the existing heads is an option but requires specialized tools and expertise.
* High-Compression Pistons: Higher compression ratios improve combustion efficiency and power, but require higher-octane fuel. This must be carefully balanced with the camshaft selection to avoid detonation.
2. External Engine Components:
* High-Performance Intake Manifold: A high-flow intake manifold (e.g., Edelbrock Performer RPM, Holley) is essential to ensure sufficient airflow into the engine. The manifold should be matched to the cylinder heads and camshaft.
* High-Performance Carburetor or Fuel Injection: A properly sized carburetor (if using carburetion) or a fuel injection system is needed to deliver the required fuel for the increased horsepower. Fuel injection offers better control and efficiency.
* Exhaust System: Headers with a suitable exhaust system (pipes, mufflers) are necessary to efficiently remove exhaust gases. Long-tube headers are generally preferred for performance gains.
* Ignition System: An upgraded ignition system (e.g., MSD) provides better spark energy and control, essential for proper combustion at higher RPMs.
3. Other Considerations:
* Cooling System: A high-performance cooling system, including a larger radiator and higher-capacity water pump, is crucial to prevent overheating.
* Oil System: A high-volume oil pump and a suitable oil cooler might be necessary to ensure proper lubrication under higher loads.
* Professional Tuning: After installing all the parts, professional dyno tuning is absolutely necessary to optimize the engine's performance, fuel delivery, and ignition timing. This ensures the engine runs safely and efficiently at peak horsepower.
In short: Reaching 400hp from a 350 requires a substantial overhaul, not just a few upgrades. The cost can easily reach several thousand dollars depending on the components used and the level of professional labor required. It's a project best undertaken by someone with significant engine building experience or with the help of a professional engine builder.
