The BMW B46 Head Stud Thread Insert Kit provides your machine shop everything needed to repair or upgrade the engine block threads on B46 engines. Designed for precision and durability, this kit allows you to restore damaged threads or prepare the block for oversized head studs for improved clamping strength. Please note, this product does NOT include head studs. Head Studs are available for purchase here. Each BMW B46 Head Stud Thread Insert Kit includes: (1) Specialized drill bit for proper thread preparation (1) High Speed Steel 3-Flute Tap (1) High Speed Steel Extended 3-Flute Tap (10) Precision stainless-steel thread inserts Red threadlocker Available in 11mm for OEM-spec head stud thread repair or 12mm for use with our Oversized Head Stud Kit, this thread insert kit ensures a secure and permanent repair capable of withstanding extreme cylinder pressure and torque loads. How these inserts work: Our insert design supports the use of both factory head bolts and high-quality aftermarket ARP head studs. These fasteners use rolled threads, which are up to 20% stronger than cut threads, and are engineered to flex and return to shape as the engine heats and cools—maintaining consistent clamping pressure on the head gasket throughout every heat cycle. Benefits of Installing Oversized Head Studs: Repair Worn or Damaged ThreadsWhen an engine block’s head bolt holes become stripped or elongated from repeated torque cycles or overheating, a standard-size stud may no longer hold properly. By drilling and re-tapping the holes to a larger diameter and using oversized studs, you restore proper thread engagement and strength—often stronger than original. Increase Clamping ForceOversized studs can have a larger shank diameter, which increases tensile strength and reduces stretch under high cylinder pressures. This is particularly beneficial for high-boost turbo where combustion pressures are extreme. Reduce Head Gasket FailureStronger or larger studs provide more uniform clamping across the cylinder head, which improves gasket sealing and minimizes the risk of head lift or gasket blowout. Not all engine blocks are suitable for oversize head stud installation. Due to differences in casting thickness, core shift, and material distribution, some blocks may not have enough surrounding material to be safely machined for larger fasteners. A skilled and experienced machinist must inspect the block and be confident in its integrity before performing any machining. Improper assessment or installation may result in cracking, coolant passage intrusion, or structural failure. All modifications are performed at the installer’s own risk. Please Note: Installing oversized head studs requires precise machining; drilling and tapping the block must be completely straight and to the correct depth.
