Everything You Need To Know About Modern Gaskets: Part 1
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If you haven’t been around race or high performance engines for some time, we have some news for you: Gasket technology is a lot different than it was even a few short years ago. Some of what you see below might be surprising. And with that, some of the practices used to install gaskets are different too. Are the gaskets and tech really that much different? You bet. With that in mind, we spoke with one of the innovators in the field, Mahle Performance regarding today’s gasket technology. Check it out.
A really good example is the all-important head gasket. Not that long ago, it wasn’t possible (or at least advisable) to run an engine with aluminum heads on an iron block fitted with a steel head gasket. You had to use some form of composition head gasket or a copper head gasket. Composite gaskets are (and were) the most common. They typically began as a basic metal core with a pliable material such as asbestos applied to both sides. Asbestos was quickly rejected in favor of less hazardous composites however the design elements are still similar: Incorporate a material that easily conforms to the imperfections of the block and cylinder heads surfaces. Install a flange or “fire ring” around the cylinder bore opening in order to retain cylinder pressure. Other types of sealant was (is) commonly applied around coolant and oil passage openings in the gasket, however the fire ring or flange is (still) typically a separate segment that must be locked in position on the gasket. That was then.
Basically, the hot ticket today is the MLS or “Multi-Layer Steel” gasket. It is a head and shoulders improvement over vintage single piece steel, copper sheet or even composite gaskets. Essentially, MLS gaskets are made up of two to five very thin sheets of spring or carbon steel stacked and riveted together. But that’s the basics.
How they came to be is this: Car manufacturers changed the way cylinder block decks are laid out. Mahle has considerable insight: “The design criteria for the later LS and many open deck applications was to limit bore distortion and extend reliability and improve performance at the same time. The days of the wire ring and flange, while functional in older designs can cause some genuine havoc in the later open deck style applications. Engineering was done with the entire assembly in mind. Older engines could survive with the bore shaped like an hour glass because the tolerance of piston clearance and ring design allowed it. The improvement to the assembly worked, so not only sealing combustion and fluids but offering a foundation for the entire engine package.”
Some of the best head gaskets in the biz are manufactured by Mahle. Case-in-point are their MLS examples. Each layer of the Mahle head gasket is constructed from 301-series stainless steel. 301-series stainless is a higher carbon content alloy that can withstand considerable mechanical force (think of cylinder pressure). Two of the layers are typically coated with a FKM or “Flouroelastomer” coating. Stop for a minute. What is a “Flouroelastomer”? It is technically called a fluorocarbon-based fluorelastomer. This polymer coating has its roots in Viton, which, as many know is a form of high tech rubber. There are now at least five different types, all with different properties. Mahle’s FKM is a proprietary example.
As pointed out above, the two outside gasket sheets are coated. The outer layers are also embossed. This is obviously done for sealing purposes (for example, around each cylinder, and adjacent to coolant and oil passages). The embossments found on the gasket actually work as “springs” to ensure that there is no leakage of fluids or combustion pressure if the cylinder head moves or expands while the engine is under heavy load. The coating helps seal off small imperfections in the machined surfaces of both the block and the cylinder heads, effectively eliminating compression, coolant or oil leaks. Meanwhile the inner center or “shim layer” is uncoated stainless steel. It is not embossed. The thickness of the inner shim layer can vary for the application. And that means the compression ratio can be juggled for the combination (more on this later). Finally, during manufacture, the outer layers are stress relieved following the embossing process. This ensures the gasket remains flat plus it provides for even pressure across the head.
What about the rivets? In the case of Mahle, the rivets are placed outside of the mating surfaces of the gasket. For example, in a big block Chevy application, there are four rivets – two on the exhaust side of the engine and two on the lifter valley side. None of the rivets interfere with sealing surfaces (or anything else for that matter).
That’s a wrap for this issue. In our next segment, we’ll dig into cylinder block and head prep for different gasket types and we’ll also investigate proper installation techniques. You might be surprised to find that modern technology has eliminated some traditional old school practices. Watch for it!
MAHLE Aftermarket Inc.
23030 MAHLE Drive, Farmington Hills, MI 48335
Phone: (800) 338-8786
Website: Mahle Performance
Click Here to Begin Slideshow
If you haven’t been around race or high performance engines for some time, we have some news for you: Gasket technology is a lot different than it was even a few short years ago. Some of what you see below might be surprising. And with that, some of the practices used to install gaskets are different too. Are the gaskets and tech really that much different? You bet. With that in mind, we spoke with one of the innovators in the field, Mahle Performance regarding today’s gasket technology. Check it out.
A really good example is the all-important head gasket. Not that long ago, it wasn’t possible (or at least advisable) to run an engine with aluminum heads on an iron block fitted with a steel head gasket. You had to use some form of composition head gasket or a copper head gasket. Composite gaskets are (and were) the most common. They typically began as a basic metal core with a pliable material such as asbestos applied to both sides. Asbestos was quickly rejected in favor of less hazardous composites however the design elements are still similar: Incorporate a material that easily conforms to the imperfections of the block and cylinder heads surfaces. Install a flange or “fire ring” around the cylinder bore opening in order to retain cylinder pressure. Other types of sealant was (is) commonly applied around coolant and oil passage openings in the gasket, however the fire ring or flange is (still) typically a separate segment that must be locked in position on the gasket. That was then.
Basically, the hot ticket today is the MLS or “Multi-Layer Steel” gasket. It is a head and shoulders improvement over vintage single piece steel, copper sheet or even composite gaskets. Essentially, MLS gaskets are made up of two to five very thin sheets of spring or carbon steel stacked and riveted together. But that’s the basics.
How they came to be is this: Car manufacturers changed the way cylinder block decks are laid out. Mahle has considerable insight: “The design criteria for the later LS and many open deck applications was to limit bore distortion and extend reliability and improve performance at the same time. The days of the wire ring and flange, while functional in older designs can cause some genuine havoc in the later open deck style applications. Engineering was done with the entire assembly in mind. Older engines could survive with the bore shaped like an hour glass because the tolerance of piston clearance and ring design allowed it. The improvement to the assembly worked, so not only sealing combustion and fluids but offering a foundation for the entire engine package.”
Some of the best head gaskets in the biz are manufactured by Mahle. Case-in-point are their MLS examples. Each layer of the Mahle head gasket is constructed from 301-series stainless steel. 301-series stainless is a higher carbon content alloy that can withstand considerable mechanical force (think of cylinder pressure). Two of the layers are typically coated with a FKM or “Flouroelastomer” coating. Stop for a minute. What is a “Flouroelastomer”? It is technically called a fluorocarbon-based fluorelastomer. This polymer coating has its roots in Viton, which, as many know is a form of high tech rubber. There are now at least five different types, all with different properties. Mahle’s FKM is a proprietary example.
As pointed out above, the two outside gasket sheets are coated. The outer layers are also embossed. This is obviously done for sealing purposes (for example, around each cylinder, and adjacent to coolant and oil passages). The embossments found on the gasket actually work as “springs” to ensure that there is no leakage of fluids or combustion pressure if the cylinder head moves or expands while the engine is under heavy load. The coating helps seal off small imperfections in the machined surfaces of both the block and the cylinder heads, effectively eliminating compression, coolant or oil leaks. Meanwhile the inner center or “shim layer” is uncoated stainless steel. It is not embossed. The thickness of the inner shim layer can vary for the application. And that means the compression ratio can be juggled for the combination (more on this later). Finally, during manufacture, the outer layers are stress relieved following the embossing process. This ensures the gasket remains flat plus it provides for even pressure across the head.
What about the rivets? In the case of Mahle, the rivets are placed outside of the mating surfaces of the gasket. For example, in a big block Chevy application, there are four rivets – two on the exhaust side of the engine and two on the lifter valley side. None of the rivets interfere with sealing surfaces (or anything else for that matter).
That’s a wrap for this issue. In our next segment, we’ll dig into cylinder block and head prep for different gasket types and we’ll also investigate proper installation techniques. You might be surprised to find that modern technology has eliminated some traditional old school practices. Watch for it!
MAHLE Aftermarket Inc.
23030 MAHLE Drive, Farmington Hills, MI 48335
Phone: (800) 338-8786
Website: Mahle Performance
Click Here to Begin Slideshow
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