F80 M3 Bent Rods – Building the S55 Engine for Big Boost

Ahmad’s F80 M3 came to us from another local shop, after hitting a wall diagnosing a reoccurring misfire. Initially they had suspected that the car had slipped timing. They removed the front crankshaft hub and re-timed the motor but there was no change. The car also suffered from excessive oil consumption so we suggested a complete tear down.

With the engine out of the car we discovered a bent rod on the misfiring cylinder. This car was running meth injection and the Pure Stage 2 turbos so we weren’t surprised to see this. Fortunately the minor bend in the rod did not cause significant damage to the cylinder wall.

We were able to clean up the cylinder walls with just .002″ of boring and honing. Once that was complete we ordered a custom set of CP pistons designed to handle 1000whp. Fortunately the S55 has twin arc wire sprayed steel cylinder bores. That allows a standard piston to be used unlike the previous generation S65 engine requiring special pistons to work with Alusil.

To ensure that this bottom end could handle whatever our customer decided to do in the future, we replaced the weak stock rods with some Carrillo rods rated for 1500 horsepower. After dyno tuning the car produced 750whp reliably on a dynoject. If you have an S55 engine in your F80 M3, F82 M4, or your M2 please contact us if you plan to hit 750whp or more. It’s best to build your bottom end up in advance prior to big turbo modifications.