Engine Valve Grinding/Lapping - Hamilton

What is a valve grind?

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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.

 

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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Good engine performance depends on valve condition. Worn guides or stems and burned or badly seated valves allow gas to escape under compression , resulting in poor starting and loss of power.

Valve springs , too, can affect engine performance. Over a period of time they weaken, causing the valves to `bounce' on their seats as they close.

Removing the valves

Compressing a valve spring.

Support the cylinder-head assembly firmly on a suitable bench or work surface. See that there is sufficient space to store parts as they are removed, and cardboard boxes and clean newspaper available to keep them clean and safe.

Undo the nuts or bolts securing the inlet manifold to the side of the cylinder head; remove it, complete with carburettor if possible.

On some engines, the carburettor is unbolted and removed before you can gain access to the manifold nuts or bolts (See Exhaust manifold gasket replacement ).

Put the manifold/carburettor assembly in a clean, safe place preferably on a sheet of newspaper.

Similarly, remove the exhaust manifold from the side of the head and place it with the inlet manifold.

On some engines, the inlet and exhaust manifolds are fitted and removed as one unit.

Undo the nuts or bolts securing the thermostat housing to the cylinder head. Ease off the cover and lift out the thermostat.

If necessary, unscrew and remove the temperature-gauge transmitter from the side of the cylinder head.

Turn the cylinder head on its side and support it on blocks to remove the valves. Place a valve-spring compressor over the valve nearest the front of the head.

Removing the collets.

Compress the valve spring until the two split, tapered collets round the top of the valve stem can be removed. Take care not to drop them, they are easily lost.

Release the compressor slowly until it is free, then remove the valve-spring assembly and withdraw the valve from the head. Place all the valve parts together for examination later. Discard the oil seals (if fitted).

Repeat the valve-removal procedure on the remaining valves in the correct order, and place the components in their order of removal on a numbered sheet of clean paper, or push them into a piece of cardboard.

Alternatively, use the old cylinder-head gasket to&#;store the valves in their correct sequence.

Each valve must be refitted in its original position on reassembly, as individual valves, valve guides and valve seats wear in different ways.

Removing carbon

Cleaning inside the manifold parts

Remove all carbon deposits from the cylinder-head combustion chambers and valve ports , using a suitable scraper, such as a blunt screwdriver, and a wire brush .

Take great care to avoid scoring the surface of the valve seats or the machined face of the head, particularly on an aluminium-alloy head.

Clean the machined cylinder-head face to remove any remains of the old headto store&#; use the smooth side of a hacksaw blade, or a paint scraper.

Again, take care not to scratch or damage the face.

Scrape until the face is smooth and flat. Modem head gaskets have a resin-coated finish which sticks the gasket to the surface and is often difficult to remove. Make sure you remove all of it.

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Cleaning the valve head using an electric drill held in a vice.

Clean the carbon from each valve in tum. Grip the valve stem in the chuck of a stand-mounted electric drill &#; or vice-mounted if necessary. Turn at slow speed, if possible, and scrape off the deposits carefully with a screwdriver.

The valve head can be smoothed using very fine emery cloth. Remember to keep the valves in their order of removal.

Inspect the face and edge of each valve, looking for grooves , pits and for other signs of damage. If the valves are burnt, bent or damaged, renew them.

Check the valve seats in the head, looking for grooves, pitting and particularly for cracking.

Slight pitting can usually be removed by grinding. More serious pitting is removed by having the valve seat recut at an engineering shop.

Wire-brushing the combustion chamber.

Clean all carbon and dirt from inside the inlet and exhaust ports, using a cup-type wire brush mounted in an electric-drill chuck. Protect your eyes with goggles.

Stubborn carbon particles can be removed by gently scraping with a blunt screwdriver, followed by the wire brush.

Checking valve guides

Check the valve stem and guide by trying to move the valve from side to side in the guide.

Check valve guides for wear by first refitting a valve into its respective guide, then raising the valve slightly off its seat.

Try moving the valve head from side to side. If the movement at the valve head is more than 0.007 in. (0.2 mm), the valve guide or the valve stem may be excessively worn - check the manufacturer's specifications, given in a service manual, or consult your local dealer.

Cylinder block with liners

Hold a block of wood over the cylinders to prevent the liners rising.

If there is too much movement, repeat the test using a new valve. If this has less movement, the old valve stem is worn and the valve must be replaced. If there is still too much movement, the wear is in the guide and the cylinder head should be taken to an engineering shop for the replacement of all the guides.

Check the valve stem and guide by trying to move the valve from side to side in the guide.

If the guides are an integral part of the cylinder head, they can be reamed - opened out - to a larger size to take new valves with oversize valve stems. This work should also be entrusted to an engineering shop.

Grinding and refitting the valves

Generally valves should be ground , or 'lapped', into their respective seats to ensure a gas-tight seal . Grind-in each valve (including new valves) by hand, using a valve-grinding tool and valve-grinding paste.

Attach the sucker on the grinding tool to the valve face.

On some modern cars the valve faces have a thin coating which must not be removed. When fitting coated valves, use an old valve to grind the valve seat.

Smear clean engine oil on the valve stem, and attach the valve head to the sucker on the end of the grinding tool.

Smear a thin film of grinding paste round the chamfered edge of the valve head and insert the valve fully into its guide.

Grind the valve in its seat by rotating the grinding tool back and forth between the palms.

Rotate the grinding tool back and forth between the palms of the hands, pressing the tool and valve into its seat at the same time.

After a minute of continuous grinding, raise the valve off its seat, revolve it about 45 degrees, then continue the grinding process for another minute.

Repeat the grinding procedure, altering the position of the valve periodically until both the valve-head flange and the valve seat have an even, matt-grey appearance, which indicates that the valve and seat are making good contact all the way round.

The valve and seat

The seat should have a matt-grey finish with no pitting or other blemishes. The valve head should have a small step between the face and the seat. A knife-edged valve should be replaced.

If slight pitting remains on the seat, use a coarser grinding paste, followed by fine paste.

When all the valves have been ground-in, remove them and place each in its order of removal.

Wash the cylinder head, combustion chambers and valve ports thoroughly with paraffin, to remove all traces of grinding paste.

Dry the head with compressed air from a tyre foot pump , and blow through all oilways and bolt holes.

Clean all traces of grinding paste from the valves, remembering to keep them in their removal order.

Smear each valve stem with clean engine oil and refit the valves to their respective positions in the head.

Fit the oil seal over the valve stem.

If there are oil seals, fit new ones over the valve stems, taking care to avoid damaging the seal lips. Always fit new valve springs.

Place the new valve spring and spring cap in position over the valve stem, noting that the close-coiled end of the spring is usually fitted next to the head.

Compress the valve spring with the compressor tool until the two split, tapered collets can be slipped into position between the spring cap and the valve stem.

Slowly release the compressor tool until both collets are locking the spring cap and valve stem together.

Remove the compressor tool and repeat the valve installation procedure on the remaining valves, in the order in which you removed them.

Cleaning the pistons and cylinder block

Scrape any carbon deposit from the piston crown.

Clean the piston crowns and cylinder-block face to remove any excess carbon and old head-gasket remains before replacing the cylinder head.

To prevent dirt or carbon particles entering the engine during cleaning, seal oil and water passages in the cylinder-block face with pieces of clean, lint-free cloth as necessary.

The cylinder bores , too, should be plugged with clean cloth to prevent dirt particles falling between the pistons and cylinder walls.

Use a scraper tool, such as the smooth side of a hacksaw blade, to carefully remove all traces of head gasket from the cylinder-block face. Take great care not to scratch or damage the face.

Rotate the crankshaft with a spanner or socket on the crankshaft pulley bolt to bring each piston to the top of its cylinder.

On engines with removable cylinders (wet-liners), hold a block of wood down firmly over the top edge of all the cylinders as the crankshaft is turned.

This prevents the cylinder liners from being lifted as the pistons rise up the bores, and ensures that the coolant seals at the bottom of the cylinder liners are not broken.

When each piston is at TDC , use a soft scraper such as a wooden block to carefully scrape carbon deposit from its crown, leaving a small ring of carbon round the outer edge adjacent to the cylinder wall.

Polish each piston crown with fine-grade emery cloth.

Cylinder block with liners

Hold a block of wood over the cylinders to prevent the liners rising.

Clean all carbon and dirt from the cylinder bores and bolt holes, using either compressed air from a tyre foot pump, or a vacuum cleaner.

Make certain there are no carbon particles lodged in the bores.

Clean the block face, cylinder bores and piston crowns with a petrol or paraffin-moistened clean cloth, and then dry them.

Be careful not to risk a fire - do not smoke, for example.

Smear a thin film of clean engine oil on each cylinder-bore wall and then remove the pieces of cloth from the oil and water passages.

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