Engine Valves / Guides / Springs

Valve cotter half. 
Sold each - 2 required per engine valve

Fits:
Porsche 356C / SC - 1963 to 1965
Porsche 911 - 1965 to 1989
Porsche 964 - 1989 to 1994
Porsche 944 - 1982 to 1991
Porsche 928 - 1978 to 1986

Click 'Zoom in' for large parts diagram.
Diagram ref no 16

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90110541700

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Valve Cotter Half.

The TRW Valve Cotter Half is a replacement valve-spring retaining collet for selected classic Porsche engines.
Sold Each.
x2 Required Per Engine Valve.

Fits:

• Porsche 356C / SC - 1963 to 1965
• Porsche 911 - 1965 to 1989
• Porsche 964 - 1989 to 1994
• Porsche 944 - 1982 to 1991
• Porsche 928 - 1978 to 1986

Diagram Ref No 16

Also known as a valve keeper, valve collet or valve lock, this small but critical component fits into the machined groove near the top of the valve stem and locks into the valve spring retainer.

Each valve requires two cotter halves. When installed together, the two halves form a tapered locking arrangement that secures the valve spring and spring retainer to the valve stem.

What This Product Does:
The valve cotter forms part of the cylinder-head valvetrain.

Its job is to mechanically lock the valve spring retainer to the valve stem.

The assembly typically consists of:

• Engine valve
• Valve spring
• Spring retainer
• Two valve cotter halves

When the valve spring is compressed during assembly, the two cotter halves are installed around the valve-stem groove.

As the spring compressor is released, the spring retainer presses against the tapered outside surface of the cotters and locks them securely into position.

This allows the spring to remain attached to the valve while the engine operates at high speed.

Symptoms Of Wear Or Failure:
Valve cotters usually do not produce gradual external symptoms in the same way as a bearing or seal.

Problems are most commonly discovered during cylinder-head inspection or after another valvetrain fault develops.

Possible warning signs include:

• Unusual valvetrain ticking
• Metallic noise from the cylinder head
• Valve spring retainer sitting incorrectly
• Visible cotter movement
• Uneven cotter seating
• Damaged valve-stem groove
• Cracked or chipped cotter
• Wear marks around the locking surfaces
• Spring retainer sitting at an abnormal angle
• Valve clearance changing unexpectedly
• Misfire following valvetrain damage
• Loss of compression
• Serious mechanical noise after a cotter releases

A correctly installed cotter should remain securely locked and should not visibly move relative to the spring retainer.

Why Replacement Matters:
A damaged valve cotter should never be ignored.

If the cotter loses its grip on the valve stem, the spring retainer can release.

This can allow the valve to drop into the cylinder.

Potential consequences include:

• Valve-to-piston contact
• Bent valve
• Damaged piston
• Broken valve guide
• Cylinder-head damage
• Combustion-chamber damage
• Severe engine failure

Because the possible consequences are so serious, questionable cotters should be replaced during cylinder-head service rather than reused.

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90110541700

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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

• 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)

Diagram Ref No 2 and 2A.

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.        

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

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93010432100

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Valve guide standard. Inlet and exhaust.
12 per engine

Fits:
Porsche 911 1965-89

Inner diameter 9,00 mm
Outer diameter 13,05 mm
Total Length 51,00 mm

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

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93010432100

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Valve lash adjuster fixture for Porsche 911

The established method of setting valve lash with a feeler gauge often provides for a "close enough" result and rarely provides for accurate, consistent, and easy to obtain precision. STOMSKI RACING's new version of an old-standby takes the "feel" out of setting valves and provides absolute precision, speed, ease of use, and consistency. By conveniently mounting a travel indicator over the adjuster of the rocker arm, STOMSKI RACING's 911 Valve Lash Adjuster allows you to quickly and accurately set and confirm the actual valve lash without settling for "close enough" or wondering whether your feel is consistent while trying to contort a feeler gauge into the far reaches of the 911 engine.

The SR097 is precision machined from 6061 aluminum and anodized for years of service on all 911 engines including 964s and 993s. Also available are a range of dial indicators including metric, digital, and compact travel indicators for use in restricted areas (pictured).

PLEASE NOTE:  this tool does not come with the gauge

Rennline valve lash tool.

Fits:
Porsche 911 - 1965 to 1989
Porsche 964 - 1989 to 1994

Product Description

Valve lash adjustments on the air-cooled 911 engine can be a frustrating and time consuming experience, even for the seasoned Porsche mechanic.
Working in close, cramped quarters can make valve adjustments an unpleasant procedure.

Finally, there is a simpler, faster and more exacting way to adjust valve lash on all air-cooled Porsche 911 engines! From the professional mechanic to the owner/enthusiast, this easy-to-use device is made to last for many years and will prove to be a valuable addition to your 911 toolbox.

• Repeatable 0.1 mm (.004 in) lash clearance settings on every valve
• Saves time and provides more accurate over traditional feeler gauge methods
• Aluminum and steel construction
• Zinc plated finish provides corrosion protection
• Laser engraved markings
• Durable box with foam insert for safe storage

Valve spring kit - high performance. 

Fits:
Porsche 911 - 1965 to 1989
Porsche 964 - 1989 to 1994
Porsche 993 - 1994 to 1998

Our Valve Springs are designed and manufactured to specifically fit the envelope of a Porsche application not a spring from another use. 

It operates a higher natural frequency than the original spring for racing and at the very least minimizes damage from over rev in track day situations. 

Please note
993 - must use 8mm Ti retainers and Aasco Seats

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HP109

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9mm Titanium valve spring retainer disc kit - high performance. 

Fits:
Porsche 911 - 1965 to 1989
Porsche 964 - 1989 to 1994

9mm Porsche 911 titanium valve spring retainers for 9mm valves. 

Can be used to directly replace OE retainers but we recommend using in conjunction with Aasco HP109  valve springs and HPSS spring seats.

Set of 12

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HP10T9

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Valve spring seat inlet and exhaust. 

Sold each - 12 per car

Fits:
Porsche 911 - 1965 to 1989
Porsche 911 turbo - 1975 to 1989
Porsche 964 - 1989 to 1994
Porsche 914/6 - 1970 to 1976

Click 'Zoom in' for large parts diagram.
Diagram ref no 14

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90110542104

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Valve spring seat kit - high performance. 

Fits:
Porsche 911 - 1965 to 1989
Porsche 964 - 1989 to 1994
Porsche 993 - 1994 to 1998

Our Steel Spring Seats pocket the inner spring of our Aasco High Performance Valve Springs.

Our Valve Springs are designed and manufactured to specifically fit the envelope of a Porsche application not a spring from another use. 

It operates a higher natural frequency than the original spring for racing and at the very least minimizes damage from over rev in track day situations. 

Please note
993 - must use 8mm Ti retainers and Aasco Seats

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HPSS

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Valve spring.
This spring pair fits all 911's from 1965 to 1994.

Fits:
Porsche 911 1965-89
Porsche 964 1989-94

Click 'Zoom in' for large parts diagram.
Diagram Ref No 13.

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90110590151

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Valve Spring
Sold each

The Porsche Valve Spring is a critical component of the valve train system fitted to numerous Porsche 911 and Porsche 964 models from 1965 to 1994. Designed to maintain precise valve operation throughout the engine's RPM range, the valve spring ensures that intake and exhaust valves close correctly after being opened by the camshaft.

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 964 (911) C2 1989-93
• Porsche 964 (911) C4 1989-93
• Porsche 964 (911) RS 3.6L 1991-93
• Porsche 964 (911) RS 3.8L 1991-93
• Porsche 964 (911) TURBO 3.3L 1991-93
• Porsche 964 (911) TURBO 3.6L 1991-93

Diagram Ref No 13

In Porsche's legendary air-cooled flat-six engines, accurate valve control is essential for maintaining combustion efficiency, engine performance, reliability, and long-term durability. The valve spring works continuously under extreme mechanical stress, cycling thousands of times per minute to keep the valve train operating correctly.

Whether you're rebuilding a classic Porsche engine, restoring a 911, or carrying out a cylinder head overhaul, replacing worn valve springs helps maintain factory performance and reduces the risk of costly engine damage.

What Does the Valve Spring Do?

The valve spring is responsible for returning the intake and exhaust valves to their closed position after each opening cycle generated by the camshaft.

Its key functions include:

• Maintaining correct valve timing operation
• Ensuring valves close fully and consistently
• Keeping the valve train under proper tension
• Preventing valve float at higher engine speeds
• Supporting engine compression and combustion efficiency
• Protecting the valve train from instability and excessive wear

Without adequate spring tension, valves may not close correctly, leading to poor performance and potential engine damage.

Why Does the Valve Spring Fail?

Valve springs are constantly subjected to compression, heat, vibration, and high engine speeds. Over time, these factors can lead to material fatigue and a gradual loss of spring tension.

Common causes of valve spring failure include:

• Metal fatigue from repeated cycling
• High mileage wear
• Prolonged exposure to engine heat
• Over-revving the engine
• Corrosion or contamination
• Performance modifications increasing valve train loads
• Age-related weakening of spring material
• Improper engine assembly or valve train geometry

As spring pressure decreases, valve control becomes less precise, particularly at higher RPM.

Common Symptoms of Worn Valve Springs

A weakened or damaged valve spring may cause:

• Loss of engine performance
• Valve float at higher RPM
• Rough idle
• Engine misfires
• Increased valve train noise
• Reduced power output Inconsistent compression readings
• Premature wear of valves, guides, and camshaft components

In severe cases, a broken valve spring can result in valve-to-piston contact and major engine damage.

When Should You Replace Valve Springs?

Valve springs should be inspected whenever the cylinder heads are removed and replaced if any signs of fatigue or wear are detected.

Replacement is strongly recommended:

• During complete engine rebuilds
• During cylinder head refurbishment
• On high-mileage engines
• When installing performance camshafts
• If valve float is present
• When spring tension falls below specification
• During preventative maintenance on restoration projects
• Whenever a spring shows signs of corrosion or damage

Many experienced Porsche engine builders replace all valve springs during rebuilds to ensure consistent valve train performance and long-term reliability.

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90110590151

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OE Match valve stem seals control oil flow between the valve stems and guides. They are replacement sealing components for cylinder-head repairs and engine rebuilding work.

Supplied each.

Fits

• Porsche 911 1968-89 (12 Per Engine)
• Porsche 924S (8 Per Engine)
• Porsche 944 (8 Per Engine)
• Porsche 944 2.7L (8 Per Engine)
• Porsche 964 3.6L (12 Per Engine)
• Porsche 964 Turbo (12 Per Engine)
• Porsche 928 (16 Per Engine)
  
  Check fitment for your specific vehicle (model, year, engine) before ordering.
  
  Diagram ref no 19
  
  What Is This Part?

A valve stem seal is a small sealing component fitted around a valve stem at the valve guide in the cylinder head. It meters the oil reaching the sliding stem-to-guide contact, allowing lubrication while restricting excess oil from passing into the engine's gas passages. The seal works alongside the valve and guide, so their condition matters to successful sealing. During cylinder-head work, the seals should be assessed together with valve-stem and guide wear rather than treated as an isolated cure for oil consumption.

What Does This Part Do?

• Meters lubricating oil: Controls the amount of oil reaching the valve stem and guide contact.
• Restricts excess oil: Helps limit oil passing down the valve guide towards the inlet or exhaust passage.
• Seals around a moving stem: Maintains its sealing contact as the valve opens and closes.
  
  Why Replace This Part?

A damaged sealing lip or a seal that no longer seats correctly can allow too much oil past the valve guide. Replacement is appropriate when inspection identifies deterioration, damage or leakage at this point, including damage sustained during dismantling or installation.

Worn guides can allow excessive sideways valve movement and prevent a replacement seal from controlling oil correctly. Check guide clearance and valve-stem condition during repairs; fitting seals alone will not correct mechanical wear in those components.

When to Replace This Part?

• Visible damage: Replace a seal with a torn lip, cracking or other deterioration found during inspection.
• Poor seating: Investigate seals that are displaced or no longer retained correctly on the guide.
• Oil consumption or blue exhaust smoke: Inspect the seals and guides as possible causes, while checking other sources of oil burning.
• Valve-guide repairs: Assess the seals when valves or guides are removed and renew those damaged or unsuitable for refitting.
• Installation damage: Replace any seal whose lip has been cut or distorted while passing over the valve-stem grooves.
  
  Where Is This Part Fitted?

Location: In the cylinder head, around the valve stem at the upper end of the valve guide, within the valve-spring area.

FAQs

• Can I replace only the valve stem seals?
  Yes, if inspection confirms the seals are responsible and the valves and guides remain serviceable. Excessive guide clearance needs separate attention.
• Does exhaust smoke always mean these seals need replacing?
  No. Smoke and oil consumption can have several causes. Confirm the source before deciding on seal replacement or more extensive engine work.
• What matters during installation?
  Follow the engine-specific procedure, protect the sealing lip from the valve-stem grooves and use the appropriate fitting tool to seat the seal without damage.
  
  Product Summary

• Product: Valve stem seals.
• Brand: OE Match.
• Supply: Each.
• Purpose: Controls oil flow at the valve stem and guide.
• Repair context: Cylinder-head sealing repairs and engine rebuilding.

Related reference numbers
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96410411107

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Valve stem seals. Price shown is for each.

Fits:
Porsche 911 1968-89 (12 Per Engine)
Porsche 924S (8 Per Engine)
Porsche 944 (8 Per Engine)
Porsche 944 2.7L (8 Per Engine)
Porsche 964 3.6L (12 Per Engine)
Porsche 964 Turbo (12 Per Engine)
Porsche 928 (16 Per Engine)

Click 'Zoom in' for large parts diagram.
Diagram Ref No 19.

Related reference numbers
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96410411107

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