Competition Coatings QLD
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Competition Coatings QLD
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Competition Coatings - valves
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The advantages of coating a valve is to extend the part life and to reduce friction.

INTAKE valve seals the combustion chamber on the intake port side of the head, prior to that it is opening to allow air and fuel to enter the combustion chamber. Intake valves usually do not suffer as severely as exhaust valves which see combustion chamber temperatures. Therefore, the primary concern is lubricating the valve stem and seat. We do this by the application of a dry film lubricant. This reduces the friction particularly in engines where oil flow is restricted to the head. the dry film takes over the bulk of the lubrication chore. It is still advisable to coat the face of the valve in the combustion chamber to help retain combustion chamber heat in the combustion chamber. This also reduces the temperature of the back of the valve so that the incoming air/fuel mixture does not pick up as much heat from the valve, as it would, if is were not coated. Normally it is not necessary to thermal barrier coat the back of the valve, though it can be done if you wish.

EXHAUST valves experience a more severe environment because the valve is seeing combustion chamber temperatures, which on a normally aspirated engine can easily reach 730 degrees Celsius. So the face of the valve definitely gets a thermal barrier coating to reduce the amount of heat the valve will absorb. The back of the stem is coated with dry film lubricant. Again this is critical on the exhaust valve stem because the heat can reduce the ability of your oil to lubricate. Consequently the permanently bonded, high pressure, high temperature lubricants work extremely well at reducing friction and wear on the valve and the guide. In some cases, it is advisable to coat the back of the exhaust valve (such as with titanium valves where metal erosion can occur due to hot gas and flame passing over the valve). On other valves it is still preferable to coat the back with a dry film to contribute to the carbon shedding so a build up of carbon does not occur on the back of the valve which can create turbulence in the exhaust flow.

By coating the back of both intake and exhaust valves after all machining work is done you permanently bond the lubricant to the areas that will contact the valve seat thus reducing wear in this area and creating a better long term seal.    This page last modified Monday March 11, 2013 at 07:36:31 PM