Valves

Valve levelling plate

Valve levelling plates, also called shims, are used to adjust the valve clearance. These shims are available in different thicknesses in order to have the right thickness for the valve clearance of your engine block. A thicker shim reduces valve clearance and a thinner shim increases valve clearance. Special tools are often required to replace the shims, which are removed with a magnet. This is to prevent a shim from falling into the engine block with all the associated consequences.

Inlet valve

The inlet valve(s) is (are) driven by the distribution and the camshaft to ensure that fresh air (and fuel) enter the cylinder. The inlet valve is usually larger than the outlet valve to allow as much mixture as possible into the combustion chamber. The valves are subjected to high thermal loads which must be removed via the valve stem and valve retainer cap. The inlet valves become less hot than the outlet valves and are therefore made of a different material. In some cases, valves are still filled with sodium for even better heat removal. These valves are also hollow inside. However, this construction is only used in outlet valves, as they become warmer than the inlet valves. When fitting new valves, it is advisable to replace the valve guides immediately, as everything has to be opened at that time.

Valve kit set

Here you will find a complete valve kit set. This set includes new valve stem rubbers which should be replaced when the clearance is too large. This is accompanied by increased oil consumption and, in some cases, even blue smoke from the exhaust when the valve stem rubbers are badly worn.

Valve guides

The valve guide provides the seal between the valve stem and the cylinder head, which must be airtight to prevent leaks. In the event of a defective valve guide, oil can run from the cylinder head along the valve stem into the cylinder, resulting in increased oil consumption. When these valve guides become wider due to wear and tear, they must be replaced. When replacing the valve guides, the cylinder head should usually be removed and the valves removed. For more information and/or advice, please contact one of our product specialists to find a suitable solution for your repair.

Valve spring cotters

The valve is mounted in the spring seat by means of the valve spring cotter. If the valve is removed, the valve spring cotters must also be removed.

Valve spring seats

The valve spring disc is attached at the top of the valve stem and it also keeps the valve spring trapped. By means of the valve spring cotter, the valve stem is fixed in the valve spring disc. The valve spring disc is pushed down by the camshaft when the camshaft twists. In this way, the valve spring is compressed and the valve opens. To disassemble the valve spring disc, a special tool is required to compress the valve spring, as it is under tension.

Valve adjusting screw

There are several ways to check and adjust valve clearance. For example, there is the valve levelling plate (shim) where the individual plate has to be replaced according to the valve clearance. Another way is by using the valve adjusting screw. To do this, a locknut must be loosened so that the rotating eccentric part can be adjusted to modify the valve clearance. When turning, the space between the valve stem and the rocker arm increases or decreases, depending on which way it is turned. When the valve clearance is within specification, re-tighten the locknut to prevent the valve clearance from slipping. When tightening the locknut, make sure that the eccentric part does not twist with it, otherwise the valve clearance may change slightly. There are special tools to stop this; see the "Tools" category.

Valve springs

The purpose of the valve spring is to (quickly) close the valve by applying pressure against the valve spring disc. It is important that the valve closes quickly because otherwise no compression can build up in the cylinder. In addition, the piston may (in an extreme case) touch the valves if they do not close quickly enough. This is the case in racing, where high speeds are realised and the valve springs can't keep up with the RPMs. Stiffer valve springs are then fitted so that they can close more quickly. Stiffer valve springs have the disadvantage that they offer more resistance to pressure and therefore more drive loss. In some cases valve springs can break, with disastrous consequences, as the loose parts in the cylinder head are scattered around.

Set of valve springs

Here you will find a valve spring set for your vehicle for the purpose of replacement. You can also opt for an upgrade valve spring set with, for example, stiffer valve springs, such as those used in racing.

Valve rotors

Due to its off-centre shape, this rotor causes a valve to rotate while being operated by a rocker arm or tappet.

Outlet valve

The valves are subjected to high thermal loads which must be removed via the valve stem and valve retainer cap. The inlet valves become less hot than the outlet valves and are therefore made of a different material. In some cases, valves are still filled with sodium for even better heat removal. These valves are also hollow inside. However, this construction is only used in outlet valves, as they become warmer than the inlet valves. When fitting new valves, it is advisable to replace the valve guides immediately, as everything has to be opened at that time.