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Exhaust hex nut for heat exchanger. Porsche 911/964/993 1965-98 - 99908500103
99908500103/1
Vehicle Group
- 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 964 (911) C2 1989-93
- Porsche 964 (911) C4 1989-93
- Porsche 993 (911) C2 1994-97
- Porsche 993 (911) C4 1994-97
- Porsche 993 (911) C2S 1994-97
- Porsche 993 (911) C4S 1994-97
- Porsche 993 (911) TURBO 1994-96
- Porsche 993 (911) TURBO S 1994-97
Information
Exhaust hex nut for heat exchanger
OE Match exhaust hex nut designed as a direct-fit replacement fastener for the exhaust heat exchanger studs on classic Porsche 911 (1965–1998) engines. This hex nut secures the heat exchanger to the cylinder heads and exhaust studs, ensuring reliable fastening in the high-heat exhaust system environment.
Sold individually. 4, 5, or 6 required, depending on car model.
Fits:
Porsche 911 1965-89 (6 for both heat exchangers)
Porsche 964 Carrera 1989-94 (4 for both heat exchangers)
Porsche 993 Carrera 1994-98 (5 for both heat exchangers)
Porsche 993 Turbo 1994-98 (4 for both heat exchangers)
Diagram ref no 5
The hex nut is used in conjunction with the heat exchanger studs and exhaust system components to clamp the exhaust heat exchanger securely in place and maintain a sealed joint between mating parts.
The exhaust hex nut’s role may seem simple, but it’s critical to the integrity of the heat exchanger and exhaust assembly:
• Secures the heat exchanger studs to the engine block/exhaust flange
• Maintains clamp force under thermal cycling and vibration
• Helps prevent exhaust leaks at the heat exchanger interface
• Resists corrosion and heat exposure typical of exhaust temperatures.
Proper fastening ensures that the heat exchanger - which routes exhaust gasses away from the cylinders and towards the muffler system - remains sealed and aligned throughout engine operation.
Function
• Fastening: Threads onto the exhaust/heat exchanger stud to clamp components
• Retention: Holds joint integrity under vibration and thermal expansion
• Seal support: Helps maintain exhaust system seal and prevents leaks
• Heat resilience: Engineered from heat-resistant material for exhaust applications.
Worn, rusted, or missing hex nuts can lead to loose exhaust joints, exhaust leaks, poor performance, and increased noise.
Although small, exhaust hex nuts play a critical role in maintaining proper heat exchanger sealing and long-term exhaust durability. Over time, exposure to extreme heat and exhaust gases can cause nuts to corrode, seize, lose clamping force, or break during removal, leading to exhaust leaks and compromised sealing at the cylinder head. Replacing them with OE Match hex nuts restores secure fastening, helps prevent leaks, protects surrounding engine components from excess heat, and preserves overall exhaust performance.
Exhaust hex nuts should be replaced whenever the heat exchanger or exhaust system is removed, if the existing nuts are corroded, seized, rounded, or damaged, or when exhaust leaks are detected at the heat exchanger interface.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99908500103
The product you are viewing cross references to these numbers
OE Match exhaust hex nut designed as a direct-fit replacement fastener for the exhaust heat exchanger studs on classic Porsche 911 (1965–1998) engines. This hex nut secures the heat exchanger to the cylinder heads and exhaust studs, ensuring reliable fastening in the high-heat exhaust system environment.
Sold individually. 4, 5, or 6 required, depending on car model.
Fits:
Porsche 911 1965-89 (6 for both heat exchangers)
Porsche 964 Carrera 1989-94 (4 for both heat exchangers)
Porsche 993 Carrera 1994-98 (5 for both heat exchangers)
Porsche 993 Turbo 1994-98 (4 for both heat exchangers)
Diagram ref no 5
The hex nut is used in conjunction with the heat exchanger studs and exhaust system components to clamp the exhaust heat exchanger securely in place and maintain a sealed joint between mating parts.
The exhaust hex nut’s role may seem simple, but it’s critical to the integrity of the heat exchanger and exhaust assembly:
• Secures the heat exchanger studs to the engine block/exhaust flange
• Maintains clamp force under thermal cycling and vibration
• Helps prevent exhaust leaks at the heat exchanger interface
• Resists corrosion and heat exposure typical of exhaust temperatures.
Proper fastening ensures that the heat exchanger - which routes exhaust gasses away from the cylinders and towards the muffler system - remains sealed and aligned throughout engine operation.
Function
• Fastening: Threads onto the exhaust/heat exchanger stud to clamp components
• Retention: Holds joint integrity under vibration and thermal expansion
• Seal support: Helps maintain exhaust system seal and prevents leaks
• Heat resilience: Engineered from heat-resistant material for exhaust applications.
Worn, rusted, or missing hex nuts can lead to loose exhaust joints, exhaust leaks, poor performance, and increased noise.
Although small, exhaust hex nuts play a critical role in maintaining proper heat exchanger sealing and long-term exhaust durability. Over time, exposure to extreme heat and exhaust gases can cause nuts to corrode, seize, lose clamping force, or break during removal, leading to exhaust leaks and compromised sealing at the cylinder head. Replacing them with OE Match hex nuts restores secure fastening, helps prevent leaks, protects surrounding engine components from excess heat, and preserves overall exhaust performance.
Exhaust hex nuts should be replaced whenever the heat exchanger or exhaust system is removed, if the existing nuts are corroded, seized, rounded, or damaged, or when exhaust leaks are detected at the heat exchanger interface.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99908500103
99908500102
99908500103
99908500101
The product you are viewing cross references to these numbers
Price: €2.68
In stock
Related products
Vehicle Group
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
Information
Exhaust Manifold Bolt. M8 x 26.
EACH - 12 Per car
Fits:
Porsche 997 C2 / C4 / C2S / C4S
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99907507400
The product you are viewing cross references to these numbers
EACH - 12 Per car
Fits:
Porsche 997 C2 / C4 / C2S / C4S
Porsche Boxster 987 2.7L 2005 -08/08
Porsche Boxster 987 3.2/3.4L 2005-08/08
Porsche 997 Carrera 2 3.6L 2005>>
Porsche 997 Carrera 2S 3.8L 2005>>
Porsche 997 Carrera 4 3.6L 2005>>
Porsche 997 Carrera 4S 3.8L 2005>>
Porsche Cayman 2.7L 987C 2006-08
Porsche Cayman S 3.4L 987C 2005-08
Diagram ref no 4.
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
99907507400
99907507400
The product you are viewing cross references to these numbers
Price: €3.65
In stock
Vehicle Group
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche Boxster 987 MKII 2.9L 2009-12
- Porsche Boxster S 987 MKII 3.4L 2009-12
- Porsche Boxster 981 2.7L 2012-16
- Porsche Boxster 981 S / GTS 3.4L 2012-16
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche 997 MKII Carrera C2 3.6L 2009-12
- Porsche 997 MKII Carrera C4 3.6L 2009-12
- Porsche 997 MKII Carrera C2S 3.8L 2009-12
- Porsche 997 MKII Carrera C4S 3.8L 2009-12
- Porsche 991.1 Carrera C2 3.4L (350 Bhp) 2012-16
- Porsche 991.1 Carrera C2S / GTS 3.8L (400/430 Bhp) 2012-16
- Porsche 991.1 Carrera C4 3.4L (350 Bhp) 2012-16
- Porsche 991.1 Carrera C4S / GTS 3.8L (400/430 Bhp) 2012-16
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
- Porsche Cayman 2.9L 987C MKII 2009-12
- Porsche Cayman S / R 3.4L 987C MKII 2009-12
- Porsche Cayman 2.7L 981 2013-16
- Porsche Cayman S / GTS 3.4L 981 2013-16
Information
Exhaust Manifold to Catalytic Converter Bolt.
M8 x 30. EACH
Fits:
Porsche 997 MKI C2 / C4 / C2S / C4S
Porsche 997 MKII C2 / C4 / C2S / C4S
Porsche 991 MKI C2 / C4 / C2S / C4S
Porsche 987 Boxster MKI
Porsche 987 Boxster MKII
Porsche 981 Boxster MKI
Porsche 987C Cayman MKI
Porsche 987C Cayman MKII
Porsche 981C Cayman MKII
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
N01024426
The product you are viewing cross references to these numbers
M8 x 30. EACH
Fits:
Porsche 997 MKI C2 / C4 / C2S / C4S
Porsche 997 MKII C2 / C4 / C2S / C4S
Porsche 991 MKI C2 / C4 / C2S / C4S
Porsche 987 Boxster MKI
Porsche 987 Boxster MKII
Porsche 981 Boxster MKI
Porsche 987C Cayman MKI
Porsche 987C Cayman MKII
Porsche 981C Cayman MKII
Related reference numbers
Related, superseded, cross reference or alternative numbers for comparison.
N01024426
90007536502
N01024426
The product you are viewing cross references to these numbers
Price: €2.46
In stock
Vehicle Group
- Porsche Boxster 986 2.5L 1997-99
- Porsche Boxster 986 2.7L 1999-02
- Porsche Boxster S 986 3.2L 1999-02
- Porsche Boxster 986 2.7L 2003-04
- Porsche Boxster S 986 3.2L 2003-04
- Porsche Boxster 987 2.7L 2005-08/08
- Porsche Boxster 987 S 3.2/3.4L 2005-08/08
- Porsche 996 C2 3.4L 1997-08/01
- Porsche 996 C4 3.4L 1997-08/01
- Porsche 996 C2 3.6L 09/01-2005
- Porsche 996 C4 3.6L 09/01-2005
- Porsche 996 C4S 3.6L 09/01-2005
- Porsche 996 TURBO 2000-05
- Porsche 996 GT2 2001-05
- Porsche 996 GT3 MKI 1999-02
- Porsche 996 GT3 MKII 2003>>
- Porsche 996 GT3 RS 2003-04
- Porsche 997 MK1 Carrera 2 3.6L 2005-08
- Porsche 997 MK1 Carrera 2S 3.8L 2005-08
- Porsche 997 MK1 Carrera 4 3.6L 2005-08
- Porsche 997 MK1 Carrera 4S 3.8L 2005-08
- Porsche Cayman 2.7L 987C 2006-08
- Porsche Cayman S 3.4L 987C 2005-08
Information
Exhaust bolt repair kit for Boxster / 996 / 997 Carrera & Cayman Gen1 1997- 2009 (Not GT3, GT2 or TT engines)
With more and more broken exhaust bolts reported on the water-cooled engines, the headache of repairing a broken bolt is becoming epidemic. Tasks ranging from a simple exhaust system update through an engine removal, are consistently plagued by snapped, rusted, and broken exhaust manifold bolts. Rarely can an accurate removal of the broken bolt be performed with the engine in the car, and even after removal, the task is time consuming and if not done carefully can lead to a damaged head or faulty repair. STOMSKI RACING's answer to these problems is the SR067, a kit that easily, accurately, and flexibly allows you to drill out the broken bolts - with the engine still in the car- saving time and headaches. A CNC milled plate indexes precisely off the broken bolts and/or bolt holes. Using our uniquely designed Thumb Screws, the SR067 plate is locked in place (by threading a Thumb Screw over a broken bolt or by using a supplied bolt threaded through the SR067 Thumb Screw). With the included pilot drills and drill guides, the faulty bolt can be drilled out, producing a perfectly perpendicular and centered hole that if necessary can be chased with an included M8x1.25 tap.
Kit includes : anodized aluminum fixture, drill bits, tap with extension, drill jigs/guides, Thumb Screws, and hardware in a sturdy storage case.
Now also includes our SR065D drill guide.
With more and more broken exhaust bolts reported on the water-cooled engines, the headache of repairing a broken bolt is becoming epidemic. Tasks ranging from a simple exhaust system update through an engine removal, are consistently plagued by snapped, rusted, and broken exhaust manifold bolts. Rarely can an accurate removal of the broken bolt be performed with the engine in the car, and even after removal, the task is time consuming and if not done carefully can lead to a damaged head or faulty repair. STOMSKI RACING's answer to these problems is the SR067, a kit that easily, accurately, and flexibly allows you to drill out the broken bolts - with the engine still in the car- saving time and headaches. A CNC milled plate indexes precisely off the broken bolts and/or bolt holes. Using our uniquely designed Thumb Screws, the SR067 plate is locked in place (by threading a Thumb Screw over a broken bolt or by using a supplied bolt threaded through the SR067 Thumb Screw). With the included pilot drills and drill guides, the faulty bolt can be drilled out, producing a perfectly perpendicular and centered hole that if necessary can be chased with an included M8x1.25 tap.
Kit includes : anodized aluminum fixture, drill bits, tap with extension, drill jigs/guides, Thumb Screws, and hardware in a sturdy storage case.
Now also includes our SR065D drill guide.
Price: €481.14
In stock