High Performance Coatings offers two coatings for pistons and valves that can be used together, or separately of each other based on needs and some class regulations in racing. HPC’s thermal barrier coating (TBC) is applied to the combustion face of the piston and a wettable solid dry film (SDF) applied to the skirt.

Probably no part of an engine undergoes greater thermal shock than pistons and valves. Yet this has no effect on the bonding properties of HPC’s TBC which has the same coefficient of expansion as aluminium. Particles are bonded with an inorganic binder which is unaffected by petroleum products. With a bond strength of 10,000 psi, this coating’s non-porous ceramic matrix improves flame travel and combustion efficiency as well as reduces oil temperature and prevents carbon buildup. HPC’s TBC process also prevents excessive heat from reaching the piston rings reducing radial tension loss due to the ring overheating. TBC applied to the combustion face of the valve prevents overheating of the exhaust valve and heat transfer from the intake valve to incoming cool air and fuel, thus providing a denser air/fuel charge. The process works equally well on both two-cycle and four-cycle pistons, is applicable to new and used parts and is repeatable.

Coating the Combustion Chamber, Face and Ports

Using HPC’s Thermal Barrier coating in the combustion chamber, inlet and exhaust ports will improve the total combustion efficiency of the engine.

Thinking of the TBC as a reflector of heat, when the spark plug ignites the fuel charge, heat from the burning fuel is reflected back into the combustion chamber causing a more complete burn. For economy adjust the engine tuning to suit or for more power increase the fuel going in.

Our SDF is applied to the skirts of the piston to reduce friction and prevent scuffing. This wettable matrix coating is a Molybdenum Disulfide based coating rather than PTFE. Moly is a higher pressure lubricant and does not “cold flow” even under pressures exceeding 150,000 psi. Also Moly attracts oil keeping an adequate film of oil on the part. PTFE will shed oil and thus becomes the only lubricant between the piston and the cylinder wall. The Moly is suspended in a thermosetting polymer binder which hardens during curing providing a permanent lubricant unlike break-in Moly sprays. SDF can also be applied to the stem of the valve to reduce friction and wear. Engine bearings are another excellent application for HPC’s SDF coating.

Valve Springs

A valve spring’s biggest enemy is heat. Heat is generated in the spring from three sources. First by cycling the spring through compression and extension. For example, try bending a paper clip back and forth, you will feel it get hot at the flex point. Second is heat generated by the friction between the coils on double and triple springs and the dampener. Third is heat absorbed by the spring from the cylinder head, especially the exhaust spring being right over the exhaust port. Cooling is achieved from oil being splashed over the spring by the rocker arms.

Many coatings have been used on valve springs. Most are PTFE based coatings, and this is fine for reducing friction between coils and dampeners, but oil will be shed by the PTFE eliminating any cooling the spring may see. Our SDF Solid Dry Film Lubricant coating is the answer. SDF not only acts as a superior high pressure lubricant but also attracts oil like steel to a magnet. Valve springs coated with SDF can retain their seat pressure up to tree times longer than uncoated valve springs.

Many camshaft manufacturers now offer coated valve springs in their line-up (we should know, HPC in USA coat many of them). But usually only their most radical springs for all out competition are coated. However, street driven cars see just as much benefit. By performance standards, a valve spring on a daily driven car is worn out by 40,000 miles. At this point even though the motor runs fine it will be down on peak horsepower and RPM capability due to the spring’s loss of tension. Remember, it is the cams job to open the valve but the valve spring’s job to close it at the right time. SDF is an excellent choice for any motor being built and is very affordable.

Oil Shedding Coatings

For those applications where you want a coating that sheds oil and other petroleum liquids, rather than retaining it, HPC has developed SO2. A major component of this coating is polytetrafluoroethylene (PTFE). This process works well in eliminating exfoliation/corrosion and oxidation on zinc, aluminium and magnesium. SO2 can be applied directly over more conventional pre-treatments such as anodising, phosphating and electroplating. It is a black-pigmented coating with temperature stabilities from –100°F (-79°C) to +700°F (371°C).

SO2 Applications :

• Inside Oil Pans
• Windage Trays
• Blower Rotors
• Inside Valve Covers
• Inside Heads & Blocks
  

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