B38 Main Stud Kit by ARP

The BMW B38 engine is compact, turbocharged, and capable of impressive performance, but its factory main bolts are a weak point when power levels increase. The ARP Main Stud Kit upgrades your B38 engine with race-proven studs, providing superior clamping force, block stability, and protection under extreme conditions.

Key Benefits of ARP Main Studs for the B38:

• Uniform Clamping Force: Ensures even pressure across main bearing caps for precise crank alignment and long-term reliability
• Improved Block Stability & Rigidity: Maximizes power transfer, improves throttle response, increases horsepower and torque
• Prevents Main Cap Walk: Keeps main caps securely in place, protecting crankshaft and engine integrity
• Reduced Fastener Stretch: High-quality ARP studs resist deformation under high RPM and high-load applications
• Protects Engine Block Threads: Precision machining and unmatched tensile strength reduce risk of stripped or deformed threads

Whether building a BMW i8, 118i, 218i, or MINI Cooper B38, ARP Main Studs provide the reinforcement your engine needs to handle boosted, high-RPM, and high-horsepower builds. This simple upgrade offers peace of mind and long-term durability for any B38 performance project.

When opting for main studs instead of factory bolts, it's important to note that the engine builder should mic the bores. Using studs may require a line hone to ensure proper fitment and alignment. A line hone is a machining process that can be used to resize and reshape the main bearing bores, ensuring that they are perfectly round and concentric. This is crucial for ensuring proper oil clearance and preventing premature bearing wear. By mic'ing the bores and performing a line hone if necessary, engine builders can ensure that the main studs are installed correctly and that the engine will perform reliably and at its best.

Installation Instructions

1. Thoroughly clean all threaded holes in the engine block. If necessary, use an ARP thread chaser to ensure clean threads and proper engagement.
2. Inspect all studs, nuts, and washers for damage and verify proper fit, length, and dimensions before installation.
3. Install the main studs into the engine block by hand until snug. Do not overtighten.
4. Install the main caps and check for proper fit, alignment, and any binding.
5. Apply ARP Ultra-Torque Fastener Assembly Lubricant to the stud threads, nuts, washers, and washer contact surfaces.
6. Install the washers and nuts and tighten them by hand. Do not substitute motor oil or other lubricants for ARP Ultra-Torque.

7. Following the manufacturer's recommended main-cap tightening sequence, torque all main stud nuts progressively in three steps using ARP Ultra-Torque:

   Step 1: 20 ft-lbs
   Step 2: 40 ft-lbs
   Step 3: 60 ft-lbs

8. After final torque, measure the main bearing bores and verify proper size, roundness, and alignment.
9. If necessary, line hone the main bores with the ARP main studs installed and torqued to specification.
10. Verify final main bearing oil clearances before engine assembly.