BMW S58 Cylinder Head Restoration & Upgrade

From Detonation Damage to Track-Ready: Restoring a Cylinder Head the 5150 Way

Not all damaged heads are destined for the scrap bin. One of our recent customers brought in a cylinder head that had suffered serious damage after a fueling issue led to detonation. The result? A melted piston, a beat-up combustion chamber, and a valvetrain that was far from healthy. But as soon as we inspected it, we knew this head still had potential—and with the right treatment, we could bring it back stronger than ever.

The Diagnosis

The initial visual inspection told us a lot: severe signs of detonation, significant chamber damage, and bent valves. But there was more. The intake and exhaust ports had clearly been “hand ported”—someone took what looked like a Home Depot Dremel to the ports and gave it their best shot. Unfortunately, while the intention may have been to improve airflow, the result was wildly inconsistent flow characteristics across all runners.

The 5150 Solution

We started by flow-testing the head to understand exactly how the DIY porting had affected performance. As expected, the airflow varied cylinder to cylinder, causing imbalance that could hurt performance—or worse, cause another failure. Using our state-of-the-art 5-axis Rottler CNC equipment, we re-machined the ports with precision, restoring symmetrical flow across all intake and exhaust runners.

Next, we tackled the damage from detonation. The combustion chamber was reconditioned, and we repaired the spark plug threads to factory-spec integrity. We then installed new high-performance valve guides to replace the worn factory units.

Since the customer supplied GSC cams and springs, we completed the valvetrain upgrade with new performance valves to replace the bent originals. Everything was measured, installed, and torqued to exact specs, ensuring this head would be ready for high-power, high-RPM operation.

 

Back in the Game

With the head fully restored, precision-machined, and equipped with performance valvetrain components, it’s now ready to go back on the engine and return to the kind of driving it was built for. Whether it’s the track, the strip, or the street—this head’s not just fixed. It’s better.

At 5150 AutoSport, we don’t just repair damage—we optimize for performance. If you’ve got a cylinder head that’s been through it, get in touch. We’ll let you know what’s salvageable, and what it will take to bring it back to life.