2003 Mitsubishi Evo 8 – Diagnosing Engine Failure

mitsubishi evo 8 engine sl autoworks

This 2003 Mitsubishi Evo 8 was brought into SL Autoworks because it was running very rough, had a cylinder 3 misfire, and the engine was eating a quart of oil roughly every 100 miles. The Evo already had some work done (listed below) so we started with running some tests and ended up performing a full engine teardown. Read on for details!

Existing Mods: 

  • Forged bottom end, HKS 272 cams
  • FP Black turbo
  • FP log manifold
  • FIC2150’s
  • Single Walbro 450, e85

Identifying The Problem

exhaust valve burnt cylinder 3 sla

After doing a leakdown test we removed the cylinder head and found one of cylinder 3’s exhaust valves damaged (burnt exhaust valve). We also identified damage to the top of the piston. 

burnt pistons mitsubishi evo 8 sla

After sharing our findings with Andrew and laying out all of his options, he decided to rebuild the bottom end of the engine in addition to the cylinder head repair. We removed the engine and performed a full teardown.

improper ring end gaps evo 8 sla

During the engine teardown, we found improper ring end gaps and damaged main/rod bearings. The previous builder caused damage to the car by dropping in the new Manley Turbo Tuff Rods, the Wiseco Pistons, and ACL Rod Bearings without refreshing the main bearings, honing the cylinder walls, or any proper “blueprinting” of parts.  

New Parts Going In

  • New 85.5mm 9.1:1 Wiseco 1400HD pistons
  • torqued plate honed
  • King PMAX Kote bearings
  • polished original crank
  • inspected and reusing turbo tuff rods
  • ARP 625 head studs
  • balance shaft delete
  • GSC S2 cams
  • Curt Brown ported and built head
  • clean and flow test FIC2150’s
  • new ID fuel filter

The new .020 overbore pistons will allow for the proper piston to wall clearance from machining to suit the needs of the power output and longevity. The new King PMAX Kote bearings are a new protective polymer coating for additional bearing protection. New bearings and a refreshed crank will allow us to set target bearing tolerances for the power and use of the car.

The Curt Brown head will allow for more airflow to the engine and a more usable power curve accompanied with cams for the turbo and allow for a larger turbo in the future. The 625 studs help keep the head on the block from the added cylinder pressure.

Finished build details coming soon!

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