Understanding the Tri-Five Chevy and Its Performance Legacy

The Chevrolet Tri-Five (1955–1957) is more than a classic car; it is a cornerstone of American automotive culture. Its combination of handsome styling, unibody construction, and the introduction of the small-block V8 created a platform that remains a favorite among builders. The small-block Chevy, especially the 350 cubic‑inch version, is legendary for its light weight, compact dimensions, and immense aftermarket support. The 400‑horsepower target is a natural goal because it roughly doubles the output of a stock 1950s small-block while remaining streetable and reliable. Building to 400 hp requires a systematic approach to component selection, engine balance, and supporting systems. This guide provides a detailed cost breakdown, performance expectations, and practical advice for completing a 400‑hp small-block build for a Tri-Five.

Setting Clear Goals for a 400‑hp Small-Block Build

Before ordering parts, define what “400 hp” means for your driving style and budget. A street‑focused build prioritizes low‑end torque and drivability, while a track‑oriented build might favor peak horsepower at higher RPMs. Decide whether you want a long‑block assembly (fully built short‑block with heads and cam installed) or a short‑block that you assemble yourself. Other key decisions include:

  • Intended use: Daily street driving, weekend cruising, autocross, or drag racing.
  • Fuel type: Pump gas (91–93 octane) is recommended for street builds; race gas or E85 may be needed for higher compression.
  • Transmission and rear end: Ensure your TH350/TH400 or manual transmission and the 10‑ or 12‑bolt rear can handle the torque.
  • Cooling system: Larger radiators and electric fans are often required to manage the extra heat.

Having clear goals prevents overspending on parts that don’t match your driving needs and ensures the build stays within budget.

400‑hp Small-Block Build Cost Breakdown

The following cost range reflects mid‑quality parts from reputable brands (e.g., AFR, Trick Flow, Comp Cams, Edelbrock, Holley). Prices vary widely based on brand, materials, and whether you buy new, used, or refurbished. Labor estimates assume professional engine assembly and installation; do‑it‑yourself builds can save $1,000–$2,000.

Base Engine Block

  • Stock 350 block (rebuildable core): $200–$500
  • Aftermarket cast‑iron block (e.g., Dart SHP): $1,500–$2,500
  • Billet main caps, machine work (bore, hone, deck): $300–$600

A production 350 block can be machined to 400 hp with proper machining. Aftermarket blocks offer thicker cylinder walls and better material but are usually not necessary for a 400‑hp street build.

Rotating Assembly

  • Forged pistons (flat‑top or dish, depending on chamber volume): $400–$700
  • H‑beam connecting rods (e.g., Scat, Eagle): $300–$600
  • Forged steel crankshaft (cast is sufficient at 400 hp): $400–$800 (for forged)
  • Balancing the rotating assembly: $200–$400

Total rotating assembly cost can range from $1,300 to $2,500 depending on material choices. A cast crank is acceptable for 400 hp and saves $200–$400.

Cylinder Heads

Heads are the single most impactful component for power. For a 400‑hp 350, a 185–200 cc intake runner with 2.02/1.60 valves works well.

  • Aluminum aftermarket heads (AFR 195, Trick Flow 195, Edelbrock E‑Street): $1,000–$1,800 (pair)
  • Iron heads (e.g., Vortec L31, Bowman rebuilds): $600–$1,000 (used with machining)
  • Valve job, guides, springs compatible with cam: $200–$400

Aluminum heads are lighter and allow higher compression without detonation. Budget $1,200–$2,200 for a set ready to bolt on.

Camshaft and Valvetrain

  • Hydraulic roller camshaft (e.g., Comp Cams XR288HR, Lunati Voodoo): $300–$600
  • Lifters (hydraulic roller), pushrods, rocker arms: $400–$800
  • Timing chain set: $80–$150

A hydraulic roller cam with approximately 230°–236° duration at 0.050” and 0.480–0.510” lift provides strong mid‑range torque and a smooth idle. Expect to spend $800–$1,600 on the complete cam kit.

Intake Manifold and Carburetor

  • Single‑plane or dual‑plane intake (e.g., Edelbrock Performer RPM, Weiand Stealth): $200–$500
  • Carburetor (600–750 cfm vacuum secondary or mechanical): $300–$700 (e.g., Holley 750 Street HP or Edelbrock 750 Thunder Series)

A dual‑plane intake favors low‑end torque for street driving; a single‑plane helps top‑end power. For 400 hp on a 350, a 650–750 cfm carburetor is ideal.

Exhaust System

  • Headers (long‑tube or shorty for Tri‑Five chassis): $400–$800 (e.g., Hooker, Hedman)
  • Mandrel‑bent exhaust pipes, mufflers, X‑pipe: $400–$1,200

Subframe clearance is tight on Tri‑Fives; many builders prefer shorty headers that fit without requiring steering column modifications. Expect $1,000–$2,000 for a complete exhaust system.

Fuel System

  • High‑volume mechanical fuel pump (or electric pump): $80–$200
  • Fuel lines, regulator, filters: $150–$300
  • Upgraded fuel tank (if necessary for electric pump): $200–$500

An electric fuel pump with a pressure regulator ensures consistent fuel delivery at high RPMs. Budget $300–$700 for the fuel system.

Ignition System

  • HEI distributor (e.g., MSD Pro‑Billet, DUI): $200–$400
  • Wires, spark plugs (e.g., NGK V‑Power, Accel): $60–$120

A tuned HEI or a computerized distributor works well for 400 hp. Consider a CDI box (e.g., MSD 6AL) for reliable high‑RPM spark, adding $200–$400.

Labor and Miscellaneous

  • Machine work (bore, hone, line bore, deck, balance): $600–$1,200
  • Engine assembly (if not done by owner): $800–$1,500
  • Installation, dyno tuning, break‑in: $400–$1,000
  • Gaskets, seals, fluids, hardware: $200–$400

Total labor and machine work: $2,000–$4,100.

Complete Build Cost Summary

  • Basic street‑build (rebuilt short‑block, Vortec heads, dual‑plane intake, good cam): $4,500–$6,000
  • Medium‑performance (aftermarket block, AFR heads, forged rotating assembly, roller cam, fuel system upgrades): $7,500–$10,500
  • Top‑end budget (billet block, custom cam, all new supporting systems, professional dyno tuning): $10,000–$13,000

These ranges assume you are starting with a core or complete engine. A turnkey crate engine from BluePrint Engines or ATK delivers 400 hp for $5,500–$7,500, often cheaper than a custom build when labor is factored in.

Performance Gains: What to Expect

A well‑sorted 400‑hp 350 small‑block transforms a Tri‑Five from a boulevard cruiser into a legitimate performer. Key metrics:

  • Horsepower and torque: 400 hp at approximately 5,600–6,000 RPM; 420–450 lb‑ft of torque at 3,800–4,200 RPM.
  • 0–60 mph: 5.5–6.5 seconds (with proper gearing and traction).
  • Quarter‑mile: 12.5–13.5 seconds at 105–112 mph (street tires to drag radials make a big difference).
  • Throttle response: Upgraded valvetrain and optimized carburetion eliminate bogging and hesitation.
  • Drivability: A hydraulic roller cam with 112–114 LSA provides a smooth idle at 700–800 RPM, making the car pleasant in traffic.

Additionally, the sound from headers and a free‑flowing exhaust is unmistakably aggressive. The Tri‑Five’s classic appearance combined with modern power makes every drive an event.

Critical Considerations for a Successful Build

Compression Ratio and Fuel

To make 400 hp on pump gas, target 9.5:1–10.5:1 static compression with aluminum heads. Avoid exceeding 10.0:1 with iron heads. Use a dynamic compression calculator to ensure your cam selection bleeds off enough pressure to run 93 octane.

Camshaft Selection

A cam that’s too aggressive will hurt low‑end torque and make the car annoying on the street. For a Tri‑Five that sees street time, choose a hydraulic roller with 220–230° duration at 0.050” and 0.480–0.510” lift. Lobe separation of 112°–114° provides a strong idle and good vacuum for accessories.

Supporting Drivetrain Upgrades

The stock Tri‑Five rear end (often a 10‑bolt) should be rebuilt with stronger axles, a limited‑slip differential (e.g., Eaton TrueTrac or Auburn Pro), and a performance gear set like 3.55:1 or 3.73:1. The transmission (TH350/TH400) should be freshened with a shift kit, higher‑stall torque converter (2,500–3,200 RPM for 400 hp), and an auxiliary cooler.

Suspension and Brakes

400 hp bends a Tri‑Five’s stock suspension. Upgrade the front coils to a 1‑inch drop spring, add a rear sway bar, and install modern disc brakes (e.g., Wilwood or CPP) for safe stopping. Subframe connectors tie the unibody together and reduce flex under hard acceleration.

Cooling System

Tri‑Fives originally ran 180°F thermostats with a small radiator. For 400 hp, use a 3‑core or aluminum radiator (e.g., Dewitts or Champion), a high‑flow water pump (Weiand or Flow‑Kooler), and a 16‑inch electric fan with a thermostat controller. Overheating is the number one killer of otherwise solid builds.

Fuel Delivery and Pressure

If you run a mechanical pump, ensure it delivers at least 6–8 psi at WOT. An electric pump (e.g., Holley Red or Blue) mounted near the tank is more reliable for high‑power applications. Upgrade the fuel line to 3/8‑inch from the tank to the carburetor.

Tuning and Dyno Time

After assembly, a professional dyno tune ($$400–$800) optimizes air/fuel ratio and ignition timing. This step can add 15–30 hp and improve drivability. Many builders skip dyno time and rely on a ”tune by ear,” but that often leaves power on the table.

External Resources for Parts and Guidance

Use these sources to research components and compare prices:

  • Summit Racing – extensive inventory of small-block Chevy parts, with customer reviews and build articles.
  • JEGS High Performance – competitive pricing on crate engines, heads, and complete rotating assemblies.
  • Chevy Hardcore – tech articles and dyno tests specific to small-block builds.
  • MotorTrend How‑To – step‑by‑step guides for small-block assembly and Tri‑Five restoration.

Conclusion

Building a 400‑hp small‑block for a Tri‑Five Chevy is a rewarding project that marries classic style with modern performance. The cost ranges from $4,500 for a smart budget build to $11,000 or more for a premium, dyno‑tuned engine. By investing in good cylinder heads, a proper camshaft, a balanced rotating assembly, and supporting systems (fuel, cooling, exhaust, drivetrain), you can achieve a reliable 400 hp that transforms the driving experience. Whether you do the work yourself or hire a shop, careful planning and realistic budget expectations will ensure your Tri‑Five runs strong for years to come.