Understanding the 4G63 Engine Platform

The Mitsubishi 4G63 engine is a turbocharged inline-four that powered the Eclipse GSX and GS-T, along with the Eagle Talon and Plymouth Laser. Its iron block, closed-deck design, and robust crankshaft make it capable of handling serious power. With proper modifications, a 4G63 can reliably produce 400 to 600 wheel horsepower. However, building to these levels requires a systematic approach and a clear budget. This article provides a detailed cost breakdown for each category of parts and labor, helping you plan a build that meets your goals without hidden surprises.

Core Engine Component Costs

Engine Block and Bottom End

The factory 4G63 block is strong, but for 500+ hp a forged bottom end is mandatory. Stock 4G63 rods are prone to bending past about 450 hp. Budget for the following:

  • Short block (new or used): $500 – $1,500. A clean used block can be machined, but a new aftermarket block (e.g., from Magnus or Dart) costs more.
  • Forged pistons and rods: $600 – $1,200. Common choices include Wiseco, Mahle, and Manley. A direct swap or custom ring gaps affect cost.
  • Forged crankshaft: $300 – $800. The stock crank is strong to about 800 hp, but aftermarket options like Eagle or Crower add safety.
  • Bearings, gaskets, and hardware: $200 – $400. Use ACL bearings, ARP main studs, and a MLS head gasket.

Total for a reliable bottom end: $1,600 – $3,900. Consider a fully assembled long block from STM Tuned if you want a turnkey solution.

Cylinder Head and Valvetrain

The 4G63 head flows well, but high lift cams and stronger springs are needed for 600 hp. Head costs depend on whether you DIY porting or buy a ready-to-run CNC head.

  • Head porting and valve job: $400 – $1,200. A basic street port from a reputable machinist improves flow without sacrificing reliability.
  • Valves, springs, retainers, and cams: $600 – $1,500. Kelford or GSC cams with Supertech dual springs handle 900+ hp.
  • Head studs and surface prep: $100 – $300. ARP studs are standard; a multi-layer steel gasket with O-rings adds safety.

Total headwork: $1,100 – $3,000. Many builders use FFWD Connection for their head services.

Turbocharger and Exhaust Manifold

Choosing the right turbo is critical. For 400 hp a Garrett GT3076R or BorgWarner EFR 6258 fits. For 600 hp step up to a GT3582R or EFR 8374.

  • Turbocharger: $1,000 – $2,500. Include a wastegate ($150–$400) and blow‑off valve ($100–$250).
  • Exhaust manifold: $300 – $900. Tubular stainless steel manifolds (like Punishment Racing) reduce spool time.
  • Downpipe and O2 housing: $200 – $600. A 3‑inch downpipe with a flex section improves flow.

Total turbo system: $1,400 – $3,800.

Fuel System

Fuel delivery must keep up with boost. At 400 hp, stock fuel lines can work with upgraded injectors and a pump. At 600 hp, a full return‑style system is needed.

  • Fuel injectors: $200 – $600. Bosche EV14 or ID1700cc injectors for E85; 1000cc for pump gas.
  • Fuel pump: $100 – $300. Walbro 255 lph is enough for 500 hp; a dual pump or brushless unit (e.g., AEM 340) for 600+.
  • FPR, lines, and rails: $200 – $500. A fuel pressure regulator (Aeromotive) and braided PTFE lines prevent starvation.

Total fuel system: $500 – $1,400.

Intercooler and Induction

Charge air cooling directly affects knock resistance and power. A front‑mount intercooler (FMIC) is the standard upgrade.

  • FMIC core and piping: $300 – $800. Choose a 3‑inch core with cast ends. Upgrade piping to 2.5 or 3 inches.
  • Intake pipe with filter: $100 – $250. A blow‑through MAF or MAP sensor setup may be required for speed density tuning.

Total charge air: $400 – $1,050.

Exhaust System

A free‑flowing exhaust is essential. Stock systems are restrictive above 350 hp.

  • 3‑inch cat‑back and downpipe: $300 – $1,000. Stainless steel lasts longer than aluminized. Include a high‑flow cat if emissions matter.

Engine Management and Tuning

Stock ECU can be chipped, but standalone or piggyback systems unlock full potential. Tuning costs also cover dyno time.

  • ECU (standalone like Link, AEM, Haltech): $1,000 – $2,000. Includes harness and software.
  • Tuning (dyno or remote): $400 – $1,500 Custom tuning from shops like ECMTuning compensates for fuel quality and altitude.

Total management: $1,400 – $3,500.

Supporting Modifications

Transmission and Clutch

The stock F5M33 or W5M33 transmission can handle 400 hp with careful driving, but 600 hp will break gears. The following upgrades are common:

  • Upgraded gear set (PPG, Jacks Transmissions): $1,500 – $3,000. Straight‑cut gears reduce whine but increase cost.
  • Clutch kit (ACT, Southbend, Clutch Masters): $300 – $800. A twin‑disc clutch holds more torque but costs more.
  • Flywheel (lightweight): $200 – $400. Reduces rotational mass for quicker spool.

Total transmission: $2,000 – $4,200.

Suspension and Brakes

More power demands better handling and stopping. Upgraded suspension prevents torque steer and improves cornering.

  • Coilover suspension: $600 – $1,500. Tein, BC Racing, or Ohlins. Corner balancing adds $300.
  • Big‑brake kit (Brembo or Wilwood): $800 – $1,800. 13‑inch rotors with 4‑piston calipers are common for 500+ hp.
  • Stainless brake lines and pads: $150 – $300. Less fade during repeated stops.

Total suspension/brakes: $1,550 – $3,600.

Wheels and Tires

Proper tires transfer power to the ground. Drag radials or 200‑TW summer tires are recommended.

  • Wheels (17x8 or 17x9): $500 – $1,200. Lightweight options like Enkei RPF1 or Konig.
  • Tires (e.g., Mickey Thompson ET Street, Michelin PS4S): $500 – $800 for a set.

Total wheels/tires: $1,000 – $2,000.

Labor Costs: DIY vs Professional

Doing the work yourself saves $1,000–$3,000 but requires tools, a clean workspace, and mechanical experience. Common professional labor estimates:

  • Engine short block assembly: $400 – $800
  • Head assembly and install: $300 – $600
  • Turbo and exhaust installation: $200 – $500
  • Wiring and ECU installation: $300 – $800
  • Dyno tuning: included in $400–$1,500 above
  • Full build (engine, drivetrain, suspension): $1,500 – $3,500

Factor in the cost of specialty tools (engine stand, torque wrench, lift rental) if you DIY.

Total Cost Estimates by Power Target

The table below aggregates the ranges discussed above for three common power goals. All figures assume a mix of new and used parts plus professional labor unless noted as DIY.

  • 400 HP Build (streetable, pump gas): $3,000 – $6,000. Uses stock block, mild head work, 255 lph pump, 1000cc injectors, and a GT3076R. Stock clutch and transmission acceptable with careful driving. DIY labor keeps cost low.
  • 500 HP Build (street/strip, E85 optional): $5,000 – $8,000. Forged rods/pistons, upgraded cams, twin‑disc clutch, and an aftermarket ECU. Tuning is essential. Expect near the upper end if you pay for professional assembly.
  • 600 HP Build (high boost, race fuel or E85): $7,000 – $10,000. Full forged bottom end, CNC head, large turbo (GT3582R or EFR), fuel system upgrade to return style, upgraded transmission, and big brakes. Professional labor almost mandatory for reliability.

Many builders spend closer to $10,000 on a 600 hp Eclipse when including unexpected costs like broken parts, extra sensors, and multiple dyno sessions. Plan for a 10–15% contingency.

Conclusion and Final Advice

Budgeting for a 4G63 Eclipse build requires understanding the trade‑offs between reliability, power, and cost. A 400 hp build can be achieved on a tight budget with careful part selection, while a 600 hp build demands a comprehensive plan and professional execution. Always factor in supporting mods like fuel system and transmission—neglected areas that cause failures. Use forums like DSMTuners for part reviews and build logs, and consult with shops like ExtremePSI for reliable sourcing. With proper planning, your Eclipse will deliver the performance you expect without exceeding your budget.