TECH5 is a regular feature where EngineLabs asks industry leaders five technical questions. This week’s guest is technical sales rep Kevyn Kistner of Cometc Gasket, Inc.

EngineLabs: When an engine builder is switching from composite to MLS head gaskets, is there a way to judge whether or not the block and cylinder head surface finish is compatible without using a profilometer? Also, please remind us Cometic’s recommendations for surface finish with MLS gaskets?

Kevyn Kistner: Generally speaking, using a profilometer is going to be the most accurate way to get a surface finish measurement off of a cylinder head or block-sealing surface. However, this tool is not typically found in your average tool box. It is possible to go to a local Tool and Die shop and purchase a set of comparative tiles. Each set is about the size of a business-card holder and contains about a dozen or so tiles that each have a different surface finish on them. One could use the tiles as a basic starting point and compare to their surfaces and it should get them in the ballpark. Cometic Gasket, Inc recommends a surface finish of 50RA or smoother for our head gaskets.

EngineLabs: What are the drawbacks of reusing MLS head gaskets? And if an engine builders chooses to reuse an MLS gasket, what are warning signs of overuse or damage?

Kistner: Cometic does not recommend the reuse of any head gasket as there is an issue with trying to define what a use is. For some, one use might be a 24-hour endurance road race, for others it could be 200,000 miles in an every day driver. What this means is that each gasket is going to act differently upon teardown and there is no way to determine how much life is let in the gasket or how effective it will be. There is simply too much at stake to take a chance on reusing a head gasket.

EngineLabs: Explain the theory behind Load Control Embossments, and if these gaskets require less clamp load, should you torque down the heads with lower torque-wrench measurements than suggested by the engine or cylinder head manufacturer?

Kistner: Our Load Control Embossment design allows for a great seal and less bore distortion. We do this by carefully designing the embossment shape on each layer to work together, resulting in a better seal at the same torque load and reduced bore distortion. When it comes to the actual torque applied to the bolts or studs that value is more critical to get the bolt or stud into a proper stretch region so that it works properly and attains the correct clamp load.

EngineLabs: Do Cometic MLS exhaust gaskets operate under the same sealing strategy as the head gaskets? Are surface finish requirements still necessary? If no, why not?

Kistner: Our MLS exhaust gaskets do operate under the same theory as our MLS head gaskets in terms of compressing an embossment in a spring stainless steel material to create a sealing element. The surface finish is not as critical though because we do not usually have to worry about sealing any fluids in the exhaust system. The surfaces should be fairly flat and free of defects to ensure a proper seal.

EngineLabs: Are there any new advancements from Cometic in gaskets designed for other parts of the engines, such as valve covers, oil pans or water pumps where leaks are problematic?

Kistner: We are always looking for ways to offer more solutions to common sealing issues found in engines of all types. We recently have brought in some new materials that will allow us to expand our product offerings and provide a better sealing option over the conventional materials currently being offered by our competitors. Advancement in graphite coated products are allowing us to build better options for intake and exhaust gaskets and laminated materials allow us to offer a reboot on the typical cork valve cover gasket. We also have been offering an aluminum foamet material (AFM) that offers great compressibility making it great for sealing imperfect surfaces sometimes found in water pump and oil pan applications. Regardless of the gasket in question Cometic has an improved design over the “parts store norm.”