Seal ring Genuine Porsche part 93010431700

Valve guide standard. Inlet and exhaust. 12 required per engine (price is each)

This is the standard valve guide used in early air-cooled Porsche 911/930 cylinder heads. It’s a plain (non-hydraulic) guide that locates the valve stem in the head; when worn it causes oil burning, loss of compression and poor valve seating — so they’re commonly replaced whenever heads are rebuilt.

What the part is (technical data / dimensions)

Application: Porsche 911 / 930 from about 1965–1989 (varies slightly by model and year; early cars both intake & exhaust, later years sometimes exhaust only). Standard size (typical OE): ID ≈ 9.00 mm, OD ≈ 13.06 mm, length ≈ 51.2 mm.        

• 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)

Why these guides should be replaced

• Valve guides are a wearing item. Replace them when any of the following occur or when you rebuild the engine head.
• Excessive valve stem play — worn guide ID internal diameter lets the valve rock and misalign with the seat , poor sealing, reduced compression and power.
• Oil consumption / smoking — worn guides allow oil to wick down the stem into the combustion chamber, causing blue/grey smoke and fouled plugs.
• Hard starting, rough idle, misfire — poor sealing / valve timing irregularities from misaligned valves.
• Valve wobble that leads to premature valve stem wear or valve seat damage — once stems or seats are damaged you need deeper surgery.
• If a guide is cracked, broken, or has excessive ovality — must be replaced.
• Whenever you remove and refinish seats / replace springs / do a full head rebuild — replacing guides at that time is cheap insurance and ensures correct alignment. 

Inner diameter 9,00 mm
Outer diameter 13,06 mm
Total Length 51,20 mm

Click 'Zoom in' for large parts diagram.
Diagram Ref No 2 and 2A.

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Related, superseded, cross reference or alternative numbers for comparison.

93010432100

The product you are viewing cross references to these numbers

Valve guide 1st oversize. Inlet and exhaust.
12 per engine. Price shown is for each.



Fits:
Porsche 911 1965-89

Outer diameter: 13,26 mm,
Bore Ø: 9,00 mm,
Length: 51,20 mm,
Fitting Position: Intake Side

Click 'Zoom in' for large parts diagram.
Diagram Ref No 2.

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Related, superseded, cross reference or alternative numbers for comparison.

93010432150

The product you are viewing cross references to these numbers

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

The product you are viewing cross references to these numbers

Fits:
Porsche 911 SC 3.0L 1974-83
Porsche 911 (930) Turbo 3.0L 1975-77

Click 'Zoom in' for large parts diagram.
Diagram ref no 25

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

93010431701

The product you are viewing cross references to these numbers

Cylinder head nut.
24 per engine. Price is for each.



Fits:
Porsche 911 1965-89 all models

Click 'Zoom in' for large parts diagram.
Diagram Ref No 17.

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

90110438204

The product you are viewing cross references to these numbers