Can you believe the end of another week is fast approaching? That’s right, another Friday is about to land on our shop floor. Now that Thursday is making its presence known, that means it’s time for another Throwback Thursday.

This week, we are taking a short trip back to March 2017 to check out, MLS Head Gaskets: There’s More To It Than Just Bolting Them In Place. Unlike conventional, composite head gaskets that use a compressible substrate, Multi-Layer Steel (MLS) head gaskets are comprised of layers of embossed steel. Most MLS gaskets consist of between three and five layers of steel, with the embossing localized around key points like cylinder bores and oil and water ports. The outside layers are treated to a thin coating that helps the gasket conform or “cold seal” to any irregularities in the surfaces of the block and head.

MLS is short for Multi-Layer-Steel. Several sheets of stainless steel are layered to give the desired thickness. An MLS gasket’s ability to protect against blow-out in high cylinder-pressure situations is due to the embossed layers acting as a “spring” to account for increased head lift.

According to Cometic Gaskets’ website, the outer layers of their MLS gaskets are embossed and coated on both sides with Viton (a flouroelastomer, rubber-based material that is heat resistant to 482 degrees). Viton is designed to meet the demands of a variety of harsh sealing environments, load conditions, and surface finishes.

In the original article, Ron Rotunno, product manager for Federal-Mogul Motorparts (Fel-Pro) explains the concept of MLS gaskets this way, “head lift occurs in any running engine. As cylinder pressure builds, the cylinder head wants to lift off the block. Some engines exhibit more head lift than others. The internal structure of the head and the number and size of head bolts play a role. What head lift does is unload the combustion seal of the head gasket and allows combustion gases to leak from cylinder to cylinder, to coolant passages, or outside the engine.”

How smooth the surface is will dictate how well the head gasket can seal. There are two measurements of surface roughness (with all values in micro-inch – µin) Ra is the average roughness height, and Rz, is the average peak-to-valley roughness height.

One of the most-asked questions about MLS gaskets has to do with being able to reuse them. We wondered if that special coating might limit the gasket’s use for mock-up and measuring. According to Micky Hale at Cometic, “Cometic head gaskets can be used in a mock-up situation and then used in final assembly with no issue. Once the engine has been run and heat-cycled, we do not recommend the reuse of the gasket. Also, with our special polymer coatings, no additional sealants are recommended.”

The focus article talks more about deck-surface finishes, head bolts and studs, and even a few things to consider when contemplating the use of MLS gaskets like those from Cometic and Fel-Pro. Suffice to say, there’s a lot more in-depth insight into this informative article, and that definitely makes it worthy of a second look. For that reason, I selected MLS Head Gaskets: There’s More To It Than Just Bolting Them In Place as this week’s Throwback Thursday showcase article.