27/08/2025
“Trust, But Verify” – Lessons From a 1000hp Evo IX Build
We recently had a Mitsubishi Evo IX brought into our shop in pieces. On paper, this was supposed to be a 1000 hp-capable engine, built in the U.S. by a well-known shop with a strong reputation. Before putting it back together, we decided to take a closer look inside to make sure everything checked out.
Pretty quickly, we noticed signs of sloppy workmanship, so instead of taking chances, we tore the engine all the way down and checked every tolerance.
Most of the problems came from poor machine work. The block deck surface was too rough for a proper MLS head gasket seal, and the cylinder hone showed inconsistencies that could have affected ring sealing. The biggest red flag, though, was the piston ring end gap: only 0.35 mm. For an engine designed to make this kind of power, that’s dangerously tight. Under high heat, the rings could expand, butt together, and micro-weld to the piston — which would have ended in catastrophic failure.
To put things right, we resurfaced the block for proper MLS gasket compatibility, refreshed the bores with a plateau finish using flex-hone brushes, and filed the compression rings to the correct spec. After that, we gave the rest of the engine a thorough inspection, and fortunately everything else was fine.
The takeaway? Even engines that come from “big name” shops with thousands of followers online aren’t always built to the standard you’d expect. If you’re investing in a high-performance build, make sure the details are verified — because overlooking them can cost you an engine.
