Removing and Grinding Valves

Removing and grinding valves
What you'll need
 Wire Brush
 Rag
 Newspaper
 Spanners
 Emery Cloth
 Wood Block
 Electric Drill
 Scraper
 Valve-spring compressor
 Paraffin
 Foot pump
 Valve-grinding tool
 Grinding paste

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
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.
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
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.
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.
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 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.

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.
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.
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.
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.
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.
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

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.
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.