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Heat Exchangers

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99908400202
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Heat Exchanger Hexagon Nut – M10
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Ensure a secure and reliable exhaust installation with this Heat Exchanger Hexagon Nut. Manufactured to original equipment specifications, this high-quality replacement hexagon nut is used to securely fasten the heat exchanger to the engine's exhaust studs, ensuring a tight, leak-free connection.

Fits:

  • 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 924 2.0L 1976-79
  • Porsche 914 (1970-1976)

Diagram ref no 7

Heat exchanger mounting hardware is continually exposed to extreme exhaust temperatures, moisture, road salt and vibration. Over time, the original nuts can corrode, seize or lose their clamping force, making removal difficult and increasing the risk of exhaust leaks. Replacing worn or damaged hardware whenever the exhaust system is removed is considered best practice for both servicing and restoration work.

Manufactured from durable, corrosion-resistant materials, this OE Match hexagon nut provides dependable clamping force and long service life, making it ideal for routine maintenance, exhaust repairs and concours restorations.

What Does the Heat Exchanger Hexagon Nut Do?

The hexagon nut secures the heat exchanger to the cylinder head via the exhaust studs.

Its primary functions include:

  • Securing the heat exchanger firmly in position.
  • Maintaining correct gasket compression.
  • Preventing exhaust gas leaks.
  • Resisting loosening caused by vibration and heat cycling.
  • Supporting proper exhaust alignment.
  • Helping maintain engine performance and efficiency.

Correctly tightened exhaust hardware is essential for a safe and reliable exhaust system.

Why Should the Heat Exchanger Nut Be Replaced?

Exhaust mounting hardware operates under extremely demanding conditions.

Common reasons for replacement include:

  • Corrosion caused by moisture and road salt.
  • Heat cycling leading to material fatigue.
  • Seized or rounded nuts during removal.
  • Damaged threads.
  • Reduced clamping force.
  • Exhaust system restoration.
  • Heat exchanger replacement.

Replacing the hardware during exhaust work helps avoid future maintenance issues and ensures a secure installation.

Symptoms of Worn or Damaged Exhaust Hardware

Typical signs include:

  • Rusted or heavily corroded nuts.
  • Seized fixings.
  • Exhaust leaks.
  • Loose heat exchanger.
  • Rattling exhaust components.
  • Broken or damaged fasteners.
  • Difficulty removing existing hardware.

Renewing the mounting hardware helps restore the integrity of the complete exhaust system.

When Should the Heat Exchanger Hexagon Nut Be Replaced?

Replacement is recommended whenever:

  • Heat exchangers are removed.
  • Exhaust gaskets are replaced.
  • Exhaust manifold repairs are carried out.
  • Engine rebuilds are performed.
  • Restoring a classic Porsche.
  • Existing nuts show signs of corrosion or damage.

Installing new hardware during reassembly helps ensure reliable sealing and long-term durability.



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99908400202
99908400202

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90007514803
Product Information
Product Information
Hexagon headed heat exchanger bolt to muffler.

Fits:
Porsche 911 1969 - 1977
Porsche 914-6 1970 - 1976
Porsche 924 1976 - 1979

Diagram ref no 6

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

90007514803
90007514802
9000751480Y
0057103
90007514803

The product you are viewing cross references to these numbers
90007514803/1
Product Information
Product Information
Hexagon headed heat exchanger bolt to muffler.

Fits:
Porsche 911 1969 - 1977
Porsche 914-6 1970 - 1976
Porsche 924 1976 - 1979

Diagram ref no 6

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

90007514803
90007514802
9000751480Y
90007514803

The product you are viewing cross references to these numbers
DISPLAYING 1 to 3 (of 3 products)
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About Heat Exchangers

Exhaust Heat Exchangers for Porsche | Engine Efficiency & Cabin Comfort

Exhaust heat exchangers play a crucial role in your Porsche’s exhaust and heating systems. They recover heat from the exhaust gases and use it to warm the cabin or assist in managing engine temperature. Built for both performance and comfort, these components ensure efficient energy transfer without compromising exhaust flow or emissions.

At Design911, we stock a wide selection of high-quality exhaust heat exchangers designed for classic and modern Porsche models. Each unit is precision-engineered for optimal heat transfer, corrosion resistance, and long-term durability. Whether you’re restoring a classic air-cooled 911 or servicing a newer model, our heat exchangers maintain proper exhaust gas routing and cabin warmth with efficiency and reliability.

What Do Exhaust Heat Exchangers Do?

An exhaust heat exchanger captures waste heat from exhaust gases and uses it to warm air before it’s directed into the cabin or engine system. This helps improve comfort and overall energy efficiency, particularly in air-cooled Porsche engines.

Core Functions:

  • Transfers exhaust heat for cabin heating or auxiliary systems.
  • Maintains consistent engine temperature by controlling heat flow.
  • Improves thermal efficiency and reduces warm-up time.
  • Supports emissions control by stabilising combustion conditions.
  • Preserves performance by ensuring balanced exhaust back pressure.

A properly functioning heat exchanger enhances both driving comfort and exhaust efficiency — essential for performance and reliability.

Why Do Exhaust Heat Exchangers Fail?

Due to continuous exposure to heat, moisture, and exhaust gases, exhaust heat exchangers naturally deteriorate over time.

Common Causes of Failure Include:

  • Corrosion and rust from condensation or road salt.
  • Cracks or leaks caused by metal fatigue or impact damage.
  • Carbon buildup restricting airflow and heat transfer.
  • Warping from repeated heating and cooling cycles.
  • Exhaust gas leakage leading to fumes entering the cabin.

A failed heat exchanger can cause loss of cabin heating, reduced efficiency, or even exhaust gas contamination inside the vehicle, making timely replacement vital for safety and comfort.

Why Replace or Upgrade Your Exhaust Heat Exchanger?

Replacing a damaged or leaking exhaust heat exchanger ensures optimal heat transfer, clean air circulation, and continued engine efficiency.

Key Benefits:
Restores heating performance for air-cooled Porsche systems.
Prevents exhaust leaks and cabin gas contamination.
Improves exhaust gas flow and efficiency.
Crafted from high-grade stainless steel for corrosion resistance.
Precision fitment for Porsche 911, 914, and other classic models.
Essential for safe, efficient operation of vintage air-cooled engines.

Modern replacements offer improved materials and engineering, ensuring greater reliability and longer service life than older designs.

Highlights:

  • High-quality replacement exhaust heat exchangers for Porsche.
  • Restores cabin heating and improves exhaust efficiency.
  • Constructed from stainless or aluminised steel for longevity.
  • Prevents harmful exhaust leaks into the vehicle cabin.
  • Perfect fit for air-cooled and modern Porsche applications.
  • Ideal for restorations, rebuilds, and performance maintenance.

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