Everything You Need To Know About Modern Gaskets: Part 1

Click Here to Begin Slideshow When we left you in the last issue, we were deep into header gaskets, intake gaskets and valve cover gaskets from the folks at Mahle Performance. Given today’s rapid advances in technology, there were considerable improvements over what we’re used to. Mahle’s R&D program truly marched those gaskets forward. And the same can be said for oil pan gaskets. While Mahle offers a wide range of oil pan gaskets for various engines, one of the neatest is their one piece setup. Here, the side rails and the end seals are combined in one assembly. What really makes it work is the rigid carrier that is used inside each pan rail. That carrier is sandwiched by a silicone rubber layer. Each pan bolt hole is reinforced. If you examine the accompanying photos, you’ll note the rails as well as the end seals also have multiple sealing beads. This setup, coupled with the fact the end seal and the rails are one piece pretty much prevents oil leaks. Finally, the example shown in the photos is manufactured with the side rails “notched” for rod clearance (stroker crank). As far as other oil pan gaskets are concerned, Mahle offers them in rubberized fiber as well as a steel core laminate with a Teflon coating on one side. They come in several different thicknesses – from 0.062-inch, all the way up to 0.185-inch, dependent upon the application and the gasket type. While we’re downstairs, let’s ponder the rear main seal for a minute. There are two different high performance materials available from Mahle – Silicone and Viton. Standard main seals were once manufactured from Nitryl rubber, but they were limited in heat resistance. That’s why most OEM’s switched to a form of polyacrylate. It offered (and still does) good heat resistance (up to 350-degrees or so) and reasonably good abrasion resistance. Silicone seals on the other hand can withstand temperatures up to 480-degrees F or so. Viton seals combine the abrasion resistance of polyacrylate with high heat resistance (up to approximately 450-degrees F or so). With silicone seals, you have to ensure the seal is properly installed. In the case of Mahle, their silicone seals include a small plastic “shoe horn”. The idea here is to use it during the installation to prevent seal damage that can be caused by contact with a sharp end on either the cylinder block or the main cap. Mahle also recommends you initially torque the main cap bolts to 10-12 foot-pounds. Then tap the crankshaft rearward (using a soft hammer). Then tap the crank forward. At this point, you can continue to torque the fasteners to spec. In any case, with a two piece rear main seal, it’s always a good practice to offset the parting line in relation to the cap. In addition, a small dab of silicone on the seal parting lines is a good idea in order to prevent leaks. On the front end of the engine, Mahle high performance and race timing covers are different than traditional paper gaskets (although they still offer paper gaskets). Here, the gaskets are composite. But there’s a twist: The timing cover gasket is based upon an embossed aluminum core with a laminated fiber exterior. The embossing works just like the embossing on the MLS head and header gaskets, sealing potential leak paths. Mahle uses the very same process for their high performance water pump (to block) gaskets, mechanical fuel pump (to block) gasket, distributor gasket along with their thermostat housing gasket. Speaking of thermostat housing gaskets: One place that’s prone to leaks on many hot rods is the thermostat housing gasket. It’s usually the result of a warped chrome housing, but there can be other factors as well. Sometimes, no amount of persuasion (or sealant) can resolve the issue. Mahle has a really cool (no pun intended) solution: It’s a composite gasket based upon a cast aluminum core with a silicone sealing surface. The gasket is 0.117-inch thick (in comparison to the previously mentioned aluminum core gasket that measures 0.034-inch thick). No additional sealer is required and obviously, the gasket is re-useable. As you can see, Mahle offers a huge array of extremely high quality gaskets for the racing and high performance world. Many of them bring innovative sealing solutions and technology to the racing world. And while we zoomed in on the Chevy big block for this series, Mahle offers gaskets for all popular high performance applications. You can download a copy of their high performance catalog (GA-40-20) HERE. For a closer look at the gaskets discussed in this segment, Click Here to Begin Slideshow.

Everything You Need To Know About Modern Gaskets: Part 1

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

Everything You Need To Know About Modern Gaskets: Part 1

Head gaskets are critical. No secret. There are a lot of different gaskets out there, but when it comes to modern tech, you can’t beat MLS gaskets such as these manufactured by the folks at Mahle.

Everything You Need To Know About Modern Gaskets: Part 1

MLS gaskets are made up of two to five very thin sheets of spring or carbon steel stacked and riveted together.

Everything You Need To Know About Modern Gaskets: Part 1

Mahle’s MLS head gasket consists of three separate pieces – all manufactured from 301-series stainless steel.

Everything You Need To Know About Modern Gaskets: Part 1

The two outside layers (one that faces the cylinder head – the other that faces the cylinder block) are coated. Mahle uses a proprietary FKM or “Flouroelastomer” coating. See the text for details.

Everything You Need To Know About Modern Gaskets: Part 1

You’ll also note the gaskets are riveted together. Those rivets are placed outside of the mating surfaces of the gasket, as shown here.

Everything You Need To Know About Modern Gaskets: Part 1

Measuring the thickness of a gasket fresh out of the package doesn’t really mean much. When gaskets are selected, they have a “compressed thickness” thickness. That’s the thickness once its torqued into place.

Everything You Need To Know About Modern Gaskets: Part 1

Aside from compressed thickness, the bore size of the gasket also has an effect upon engine static compression ratio. The text offers more insight.

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