The Chevy 350 small-block V8. A legend. A cornerstone of American automotive history. But for those seeking to transcend the boundaries of its already impressive capabilities, the allure of twin turbocharging is undeniable. This isn't just about adding horsepower; it's about transforming a classic into a modern, high-performance powerhouse. This guide will explore the nuances of building a twin-turbo Chevy 350, covering everything from crucial components to tuning considerations.
Choosing the Right Turbochargers
The heart of your twin-turbo setup lies in the turbochargers themselves. Selecting the right ones is critical, impacting performance, reliability, and drivability. Factors to consider include:
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A/R Ratio: This describes the area of the turbine wheel divided by the area of the turbine outlet. A lower A/R ratio offers quicker spool-up (faster boost), ideal for street driving and lower RPM applications. A higher A/R ratio delivers more power at higher RPMs, beneficial for drag racing or dedicated track use. Finding the sweet spot depends on your intended application.
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Compressor Wheel Size: Larger compressor wheels yield higher horsepower potential but often at the cost of slower spool-up. Smaller wheels provide quicker boost but may limit ultimate horsepower. Consider your engine's displacement and desired power goals when making this selection.
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Turbine Wheel Size: Similar to compressor wheels, the turbine wheel size influences spool-up and power potential. Matching the turbine wheel size to the compressor wheel is vital for balanced performance.
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Turbocharger Type: Consider the type of turbocharger (ball-bearing, journal-bearing) which affects efficiency and lifespan. Ball-bearing turbos generally offer better response and longevity but come at a premium price.
Turbo Manifold Considerations
The exhaust manifold is a crucial component. A well-designed twin-turbo manifold ensures efficient exhaust gas flow to the turbochargers, maximizing performance and minimizing backpressure. Options include:
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Log-Style Manifolds: Offer individual runners for each cylinder, potentially improving flow characteristics, but often more expensive and complex.
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Merging Manifolds: Combine exhaust gases into fewer runners before reaching the turbochargers. Generally less expensive but may compromise flow compared to log-style manifolds.
Careful consideration of material (stainless steel is preferred for durability and heat resistance) is also crucial.
Internal Engine Upgrades: Building a Solid Foundation
Simply bolting on turbos won't unlock the full potential of your Chevy 350. Internal upgrades are essential to handle the increased power and stress:
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Forged Internals: Forged pistons and connecting rods are paramount to withstand the higher cylinder pressures and temperatures generated by forced induction.
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Strengthened Crankshaft: A robust crankshaft is crucial to prevent catastrophic failure under high loads.
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High-Flow Oil Pump: Ensuring adequate lubrication is critical under increased stress, so a high-flow oil pump is essential.
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Head Studs: Replace the factory head bolts with head studs to provide increased clamping force and prevent head gasket issues.
Fuel System & Management: Controlling the Power
With forced induction, fuel management becomes critically important. You'll need:
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High-Flow Fuel Injectors: These are needed to supply the increased fuel demands of the engine under boost.
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Fuel Pump: An upgraded fuel pump capable of delivering a sufficient volume of fuel is essential.
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Engine Management System (EMS): A standalone engine management system (such as an aftermarket ECU) is necessary for precise tuning and control of fuel delivery, ignition timing, and boost pressure. This allows for adjustments tailored to your specific setup.
Cooling System Enhancements: Keeping it Cool Under Pressure
Increased power means increased heat. You'll need upgrades to manage heat:
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Larger Radiator: A larger radiator with increased cooling capacity is critical.
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High-Flow Water Pump: A high-flow water pump ensures adequate coolant circulation.
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Intercooler: An intercooler is essential to cool the compressed intake air, minimizing the negative effects of heat on performance and reducing the risk of detonation.
Tuning and Dyno Testing: Fine-tuning for Optimal Performance
Professional dyno tuning is crucial to optimize performance, ensuring safe and reliable operation. A tuner can adjust fuel maps, ignition timing, and boost levels to maximize power and efficiency while preventing engine damage.
Conclusion: The Journey to Twin-Turbo Perfection
Building a twin-turbo Chevy 350 is a rewarding but challenging undertaking. It requires careful planning, attention to detail, and potentially significant investment. However, the result—a potent, responsive, and exhilarating machine—is well worth the effort. Remember to consult with experienced engine builders and tuners throughout the process. This ensures a successful build and ultimately, the unleashing of the beast within your classic Chevy 350.
