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Engine Bolts / Studs

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90110438204/1
Product Information
Product Information

Cylinder Head Nut 
Sold each - 24 required for the 911

Maintain the integrity and reliability of your Porsche engine rebuild with this OE Match Cylinder Head Nut 90110438204. Designed for use on Porsche 356B, 356C, 912 and classic 911 air-cooled engines, this precision-engineered fastener plays a critical role in securing the cylinder head assembly to the engine.

Fits:

  • Porsche 911 1965-1968 2.0L / 912 SWB (F)
  • Porsche 911 1968-1973 2.2L / 2.4L / 2.7L RS LWB (F)
  • Porsche 911 1974-1977 2.7L / 1976-77 3.0 Carrera
  • Porsche 911 1978-1983 3.0L / SC
  • Porsche 911 1984-1986 3.2L
  • Porsche 911 1987-1989 3.2L G50
  • Porsche 911 1975-1977 3.0L Turbo (930)
  • Porsche 911 1978-1989 3.3L Turbo (930)
  • Porsche 356B 1959-63
  • Porsche 356C 1963-65

Diagram Ref No 17

Although small in size, cylinder head nuts are among the most important fasteners in any engine. They provide the clamping force required to maintain an effective seal between the cylinder heads, cylinders and engine case, ensuring correct compression, combustion efficiency and long-term engine reliability.

Manufactured to OE Match specifications, this cylinder head nut is ideal for engine rebuilds, top-end overhauls, cylinder head refurbishment and concours restorations.

What Does a Cylinder Head Nut Do?

The cylinder head nut secures the cylinder head assembly to the engine using the cylinder head studs.

Its primary functions include:

  • Maintaining cylinder head clamping force
  • Ensuring correct cylinder sealing
  • Supporting combustion chamber integrity
  • Maintaining engine compression
  • Preventing cylinder head movement
  • Supporting reliable engine operation
  • Helping prevent oil and combustion leaks

Correct clamping force is essential for maintaining engine performance and durability.

Why Do Cylinder Head Nuts Fail?

Cylinder head nuts are exposed to repeated heat cycles, vibration and engine loads throughout their service life.

Common causes of deterioration include:

  • Corrosion
  • Thread wear
  • Fatigue from repeated heat cycles
  • Over-tightening
  • Incorrect installation procedures
  • Engine overheating
  • Age-related degradation
  • Damage during previous rebuilds

In older air-cooled Porsche engines, decades of service can leave original hardware weakened or unsuitable for reuse.

Symptoms of Worn or Damaged Cylinder Head Hardware

Potential warning signs include:

  • Loss of cylinder sealing
  • Compression leaks
  • Oil seepage around cylinder heads
  • Difficulty achieving correct torque settings
  • Damaged threads
  • Corroded hardware
  • Uneven clamping loads
  • Engine rebuild inspection failures

Many of these issues are discovered during engine disassembly rather than during normal operation.

When Should Cylinder Head Nuts Be Replaced?

Replacement is strongly recommended when:

  • Rebuilding an engine
  • Carrying out a top-end overhaul
  • Replacing cylinder head studs
  • Refurbishing cylinder heads
  • Corrosion is present
  • Threads show signs of wear
  • Factory specifications require replacement

Most professional Porsche engine builders replace critical fastening hardware during major engine work to ensure long-term reliability.

Why Replacement Matters

Reusing worn or damaged cylinder head hardware can compromise engine sealing and reliability.

Benefits of replacement include:

  • Correct clamping force
  • Improved sealing performance
  • Reduced risk of leaks
  • Improved engine reliability
  • Professional rebuild standards
  • Long-term durability
  • Factory-correct restoration quality
  • Greater peace of mind

For classic Porsche engines, replacing critical hardware is inexpensive insurance against future engine issues.



Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

90110438204
90110438203
90110438202
61610438200
90110438200
93010438201
90110438204

The product you are viewing cross references to these numbers
53901118/1
Product Information
Product Information
Cylinder head stud. Porsche 912 / 356B / 356C

oematch

Fits:
Porsche 912
Porsche 356 B
Porsche 356 C

Click 'Zoom in' for large parts diagram.
Diagram ref no 2

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

53901118
53901118

The product you are viewing cross references to these numbers
90008214201L
Product Information
Product Information
HEX HEAD BOLT M12X1,5X110MM (extra long)

This Item is an Original Porsche Part found by using our original Porsche Part Number Search. If you are ordering parts via this method it is your responsibility to make sure that you enter and purchase the correct products for your vehicle. Please only use the searched product if you are sure of the part numbers as parts cannot be returned if ordered incorrectly.

Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.

90008214201L
91137504300
90008214201

The product you are viewing cross references to these numbers
DISPLAYING 1 to 3 (of 3 products)
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About Engine Bolts / Studs

Precision Engine Bolts & Studs – Strength, Accuracy, and Reliability for Porsche Engines

Engine bolts and studs are the unsung heroes of your Porsche’s powerplant — small but vital components that ensure structural integrity under extreme stress. From securing cylinder heads and connecting rods to fastening crankcases and manifolds, every fastener must deliver uncompromising strength, precision, and clamping force to maintain your engine’s performance and reliability.

At Design911, we offer a comprehensive selection of standard and high-performance bolts, studs, nuts, and fasteners designed specifically for Porsche engines. Each high performance component is precision-engineered from high-tensile steel, titanium, or ARP-grade alloy, delivering exceptional resistance to heat, vibration, and torque fatigue.

Whether you’re rebuilding a classic air-cooled 911 or tuning a modern GT model, our manufacturer-quality fasteners guarantee secure fitment, consistent torque retention, and long-term durability.

What Do Engine Bolts and Studs Do?

Engine bolts and studs hold critical components together under immense pressure. They maintain precise torque and tension, ensuring the engine block, heads, and internal assemblies remain perfectly sealed and aligned.

Core Functions:

  • Provide secure clamping force for key engine assemblies (head, crankcase, rods, etc.).
  • Maintain torque integrity under thermal expansion and vibration.
  • Prevent component movement, preserving internal clearances and sealing surfaces.
  • Support rebuild precision, allowing components to be serviced repeatedly without distortion.

Motorsport-grade fasteners are designed to handle repeated torque cycles and extreme stress, making them essential for both performance tuning and professional engine restoration.

Why Do Engine Bolts and Studs Fail?

Over time, fasteners experience stretching, fatigue, and corrosion from heat, oil exposure, and repeated torque cycles. Even the strongest bolts have a finite service life — and failing to replace them can lead to catastrophic engine damage.

Common Causes of Failure Include:

  • Metal fatigue or stretching from repeated torque applications.
  • Corrosion and oxidation, especially in humid or high-heat environments.
  • Over-tightening or under-torquing, compromising clamping force.
  • Thread wear or damage from improper installation or debris.
  • Thermal cycling, weakening material structure over time.

Replacing aged or stressed bolts and studs during every rebuild or major service ensures your Porsche’s engine remains structurally sound and leak-free.

Why Replace with Precision-Engineered Bolts and Studs?

Upgrading to high-performance fasteners delivers the security and strength demanded by Porsche engines. Precision-engineered bolts and studs ensure consistent torque retention, improved reliability, and extended component life — especially in high-load or high-temperature conditions.

Key Benefits:
Superior clamping strength and torque retention for critical assemblies.
High fatigue resistance, preventing loosening or failure under pressure.
Improved corrosion protection with zinc, nickel, or black oxide coatings.
Ideal for rebuilds, upgrades, and performance tuning applications.
Precision-thread machining ensures repeatable installation and alignment.
Available in titanium and high-tensile steel for maximum strength-to-weight ratio.

These bolts and studs provide the perfect balance of motorsport-level performance and road-going durability, keeping your Porsche engine secure mile after mile.

Highlights:

  • Comprehensive range of bolts, studs, and fasteners for Porsche engines.
  • Manufactured from ARP-grade steel, titanium, or high-tensile alloy.
  • Precision-machined threads for perfect alignment and consistent torque.
  • Improved resistance to heat, corrosion, and vibration.
  • Essential for rebuilds, tuning, and restoration projects.
  • Designed for air-cooled and water-cooled Porsche engines.

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