What is a grinding valve?

A valve job is the colloquial term for resurfacing the mating surfaces of the poppet valves and their respective valve seats that control the intake and exhaust of the air/fuel mixture in four stroke internal combustion engine, replacing valve oil seals, replacing any deficient valve springs, and otherwise bringing the components of a cylinder head up to manufacturer&#;s spec.[1] A resurfacing of the head&#;s meeting surface with the engine block to true it is often done at the same time if a head has been removed from the engine.

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Some reasons that may induce the need for a valve job in a modern passenger car include: excessive RPM, high mileage, overheating, material failure, corrosion, and foreign object damage (FOD).

History

In the earliest automotive engines, the valves needed to be removed and the sealing surfaces sanded, ground or lapped multiple times during the life of a typical engine. As the decades passed, however, engines ran cleaner and the addition of tetraethyllead in gasoline meant that such maintenance became less frequent. Today, valve jobs are rarely done on passenger cars for the purpose of maintenance, although they are still quite common with high-performance cars.

Description

A valve job is best done with grinding stones and either electric or pneumatic tools. Lapping compound and a lapping tool may be used, and is more economical for home auto repair, however lapping will only provide limited results and will not be effective on a valve or seat with anything more than very light wear or damage.

Modern engines have cylinder heads made of either iron or aluminum. Iron cylinder heads most often have integral iron valve seats. These seats are the softest and most susceptible to wear among modern engines. Much softer yet aluminum cylinder heads, however, have replaceable pressed-in hardened steel valve seats. These are significantly stronger than the integral seats of an iron head, and can be relatively easily swapped out as needed. If an integral iron seat needs to be replaced, the seat must be milled to allow the insertion of a new seat. The new seat is then installed with application of a high-strength metal glue/adhesive. Once installed, the seat is ground to the correct angle and width.

Valves and seats must have the same angle to mate properly. That angle is usually 45 degrees, but 30 degrees can be found in many modern applications. The mating angle is often accompanied by top and bottom angle cuts that are 15 degrees from each side of the mating angle (e.g. for a 45 degree seat, the top and bottom angles would be 30 and 60 degrees respectively). This method increases air-flow, which gives mild horsepower, response, and efficiency improvements.

Valves are inspected for damage such as cracking, pitting, channeling, and burning that will prevent proper operation and could lead to catastrophic failure. Pitting is permissible in small amounts, but should not be present on the valve face, margin, or stem. Channeling is a result of uneven heating of a valve (typically from improper seating during operation), and is evident by heat discoloration in an oval shape on the bottom of the valve and often visible at the base of the valve stem. Channeling that continues will lead to a burnt valve (the melting away of a portion of the valve). If an engine has been subjected to excessive RPM or sudden stoppage, all valves should be inspected for straightness, as a bent valve or valve stem will quickly lead to failure, and often damage other parts such as pistons, cylinder walls, other valves, valve guides, and valve-train components.

Some older cars have relatively soft valve seats that wear faster when operated without leaded fuel. These usually can be updated with hardened valve seats that resist wear, regardless of whether leaded or unleaded fuel is used.

References

What is a valve grind?

The valves in an engine have several functions. First, they must allow the intake of fuel and air. Then they must seal the engine. As engine combustion takes place, the exhaust valve must also allow the burned gases to leave the combustion chamber.

A valve grind (commonly referred to as a valve job or valve lap) can be crucial for proper functioning valves/seals. It is the process of smoothing out the engine valves so that they are effectively able to seal in the valve seat in the cylinder head to completely seal the engine&#;s combustion chamber.

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When do you need a valve grind / job?

As your vehicle&#;s mileage increased, the valves can degrade and need repair. This is due to constant movement and engine heat. Due to advances in valve metal technologies, most modern engines will never need a valve grind. However if there is a problem with the valve, valve seat or valve tappet or rocker arm, then the cylinder head might need to be removed to fit a new intake or exhaust valve. At this point the valve(s) may need to be lapped in, or have a valve job / grind. 

Older vehicles (pre &#;s) where far more prone to burning valves, and often needed valve grinds on a regular basis.

A valve job gives mechanics the opportunity to thoroughly inspect the rest of your engine including the cylinder heads and engine block. Any cracks or leaks in these components can lead to oil leaking out of your car and overheating.

Symptoms of valve damage include:

• Increased fuel consumption

• Engine running rough

• White exhaust smoke

• Chuffing noise from the engine exhaust pipe

• Lack of engine power

Learn more about engine valve failure >

What does a valve grind consist of?

During a valve grind, the engine cylinder head is typically removed to access the valves. The process involves the following steps:

1. Valve Inspection: Each valve is inspected for signs of wear, pitting, or damage. This helps determine whether the valve can be restored or if it requires replacement.
2. Valve Lapping: Valve lapping involves applying a lapping compound (a fine abrasive paste) to the valve face and rotating it against the valve seat. This back-and-forth motion helps grind and smooth both the valve and seat surfaces, promoting a proper seal.
3. Valve Clearance Adjustment: While performing a valve grind, it is common to check and adjust the valve clearances (also known as valve lash or tappet clearance). This ensures that the valves open and close at the correct intervals and reduces the risk of valve interference with the pistons.
4. Valve Seal Replacement: In some cases, worn or damaged valve seals may need to be replaced during a valve grind. Valve seals help control oil consumption and prevent oil from entering the combustion chamber.
5. Reassembly and Testing: After the valves are ground and any necessary replacements or adjustments are made, the cylinder head is reassembled, and the engine is tested for proper operation.

The valve grind process aims to restore optimal sealing and improve engine performance by enhancing compression and reducing leaks. It can be performed as part of regular maintenance or as a repair procedure when valve-related issues are identified.

Benefits of an Engine Valve Grind:

• Improved Compression: Valve grinding restores the proper sealing between the valves and valve seats, improving compression within the engine cylinders. This leads to enhanced engine performance and power.
• Enhanced Fuel Efficiency: With improved compression, the engine operates more efficiently, leading to better fuel economy. Properly sealed valves reduce the risk of fuel leakage and optimize the combustion process.
• Restored Valve Seating: Valve grinding removes irregularities and wear from the valve and valve seat surfaces, ensuring proper contact and sealing. This helps prevent compression loss, oil consumption, and potential engine misfires.
• Increased Valve Lifespan: By grinding the valves, their seating surfaces are renewed, reducing wear and promoting longevity. This extends the lifespan of the valves and can delay the need for valve replacements.
• Smoother Engine Operation: Properly ground valves result in smoother engine operation, reducing vibrations, noise, and potential valve-related issues. This contributes to a more comfortable and enjoyable driving experience.
• Prevention of Oil Leaks: Valve grinding eliminates gaps and imperfections that can lead to oil leaks into the combustion chamber. This helps maintain proper lubrication and prevents oil contamination, enhancing engine reliability.
• Restored Valve Timing: During a valve grind, valve clearances are checked and adjusted if necessary. This ensures that the valves open and close at the correct intervals, maintaining proper valve timing and preventing interference with the pistons.

Engine Valve Grinding, Servicing & Maintenance in Hamilton

Proper engine maintenance can greatly extend the life of your vehicle.  At Grimmer Motors, we can remove your engines cylinder head and organise reliable, high-quality valve repair and replacement. This will allow for your engine to run healthily. 

For engine valve grinding and maintenance in Hamilton, contact Grimmer Motors today!

Please Note &#; we don&#;t generally stock or supply just &#;parts only&#; for this service. We are a general automotive repair workshop. If you are able to bring your vehicle to us, we can diagnose the problem, find and fit the necessary parts, or organise the appropriate service for you.

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