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Friction Discs

Friction Discs or Diamond Washers – A New Era

 

Component downsizing and cost saving during manufacture has pushed vehicle manufactures to look for other ways of carrying out what used to be a simple undertaking. One example is moving away from keyways on high load components such as camshafts, crankshafts and injector pumps.

The main fastening bolts need to be firmly attached so that they can absorb the applied torque without slipping, and the manufacture will always specify a torque setting on these bolts, which can be as high as 240nm or higher on some applications (plus a degree setting if the bolt is TTY).   With the keyways gone, the bolt itself is not always enough to transfer the load and prevent slipping.   Usually if we want to transfer greater torque, we need larger and therefore heavier and costlier components.

 

However using a friction disc or washer in between the components locks them together firmly and allows for the transmission of four times the amount of torque. These friction discs or washers are coated on both sides with a nickel matrix. The nickel is embedded with a fixed amount of diamond particles that have a specified size. If the disc is mounted between two engine parts, the hard diamond particles are pressed into the mating surfaces and locks them together. To ensure the washer works reliably it is important to replace it whenever the connected components are removed or their positions disturbed.

 

Not all engines require friction disks so be sure to check with the manufacturer.  We have many customers re-fit cylinder heads and balancers, only to have the crank or cam pulley slip and bend valves or cause other internal damage.  If your unsure give Southside Cylinder Heads a call, were happy to help in any way

 

Warning – because these washers and shims are located behind pulleys or sprockets they can easily fall when the larger component is removed.  They could end up in the sump or jammed into an awkward spot without being noticed.

 

 

 

 

 

 

 

 

 

 

 

 

 

A Basic Guide to Engine Valve Failure

Auto-Engine-Valves-320x200

Engine Valves

The valves in your cylinder head are a vital component of your engine and undergo enormous stresses, opening and closing up to 2500 times every minute under normal operating conditions. When one or more of these valves are damaged, the result can be anything from reduced power and poor fuel consumption, to complete engine failure.  The two most common types of valve failure are bent/broken valves and burnt valves.

Bent Valves

The most common failure of valves is bending or breaking as a result of contact with the pistons. The valves contacting the top of a piston is due to incorrect engine synchronization caused by timing chain/belt breakage and incorrect fitting of new belts and chains. If you suspect your engine may have bent or broken valves, it is crucial not to attempt to start the engine as this may result in more costly damage being caused to the cylinder head, pistons and cylinder bores.

The bent valves above are a result of a fatigued timing belt that has broken. Your timing belt doesn’t last forever and needs to be replaced according to the manufacturer’s service guidelines. Replacing your timing belt is cheap insurance against costly engine damage.

Burnt valvesValve-Piston-Diagram

The other common type of valve failure is valve burn, or burnt valves. Essentially this is caused by combustion gases escaping between the valve and valve seat when they are not sealing correctly. The hot combustion gases are forced past the valve which starts to burn away the edge of the valve, progressively getting worse the longer it is left without being rectified. Normally this type of failure affects the exhaust valves only, but it can also damage the intake valves.

A burnt valve will cause issues with your vehicle’s performance and fuel consumption. Rough idle, reduced power, backfiring, and misfire are all symptoms of valve burn. If your engine is showing symptoms like these, we recommend you get your car checked by a trusted mechanic, as continual driving with a burnt valve will cause more damage to your engine, and will in turn cost more to repair in the long run.


Possible causes of burnt valves are:

Bent-Valves-Caused-By-A-Broken-Timing-Belt-320x200

Bent valves caused by broken timing belt

  • Excessive localized heat
  • Combustion gases escaping past the valve and concentrated at only one point
  • Irregular valve sealing with cylinder head valve seat. Carbon residues generated by irregular combustion (poor mixture) will appear at the seat region and will jeopardize the sealing between the valve and its seat
  • Deficient refrigeration is another factor, due to partial obstruction of the cylinder head cooling.  As a consequence, the valve is cooled inadequately
  • Incorrect valve clearance can jeopardize the valve sealing and also cause this type of failure
  • Running a dry fuel such as L.P.G resulting in inadequate lubrication of the valve seat, causing the valv
    A-Valve-Starting-To-Burn4

    A Valve Starting To Burn

    e seat to fail and consequently, the valves

To help prevent this type of failure, there are a few things you can do. Maintain a clean, efficient cooling system so the engine does not run too hot,  use good quality fuels to help prevent carbon build up on the valve seats, and have your mechanic regularly check the valve clearances are within specifications.

If your vehicle is using an aftermarket L.P.G fuel system, you must check that the engine is L.P.G compatible (most are NOT). In the event your engine is running L.P.G but is not L.P.G compatible, valve failure is imminent. It will generally be less costly to have your cylinder head removed and modified for L.P.G before the valves start to burn, rather than wait until the damage is done. Once the L.P.G modifications are complete, it will be safe to use

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Burnt Exhaust Valve

the L.P.G without damaging your engine.