Horsepower levels have an impact on everything when it comes to choosing the right engine components. Head gaskets and the sealing practices used to keep cylinder pressures inside the engine are no different. It seems very few builds these days remain in stock form, therefore, more often needs to be done to ensure cylinder head sealing doesn’t become a limiting factor to how much boost pressure and power your engine can make.
The high boost and high horsepower seen these days can easily cause flex in the cylinder head or block, which can result in a blown head gasket. This typically means significant damage to the engine block and head. Due to the extreme conditions of many racing engines, head gasket failures happen enough that engine builders, and the gasket manufacturers, work to make sure they happen less. We caught up with a few gasket manufacturers to understand the latest in head gasket manufacturing and technology, as well as the best techniques used to seal engines these days.
Looking back at 2024 and into early 2025, gasket manufacturers haven’t slowed done in terms of releasing new products that cover more engines and vehicles. In the case of Mahle Aftermarket, the company has eight new head sets, either out now or coming soon, that cover over 3.7 million vehicles in operation between 2019-2024. Additionally, Mahle has seen a high demand for a comprehensive head gasket set for the 2017-2021 6.6L Duramax.
“Mahle’s continuing market strategy benchmarks ‘coverage’ by whether a head gasket set is available for a particular engine application,” says Ron McCrum, gasket team product manager for Mahle Aftermarket North America. “Other gasket suppliers may claim ‘coverage,’ but that could be defined as an oil pan gasket, or a water outlet gasket, or another ancillary sealing product, whereas a head set should be the defining minimum for coverage.”
As OE manufacturers and aftermarket suppliers continue to utilize multi-layer steel (MLS) gaskets for a majority of applications, manufacturers like Cometic also continue to add engines to their growing list of part numbers.
“We’re always exploring new applications, like expanding options for the Ford Godzilla platform and the new Dart Gen III Hemi block,” says Micky Hale of Cometic Gasket. “Staying in close contact with other block and head manufacturers keeps fresh ideas and innovative products flowing our way. We’ve been putting a lot of focus on our MLX gaskets to ensure maximum sealing. Our dual-stopper MLX has proven to be a success in high-boost applications and diesel engines. Plus, we’re continuing to expand the MLX line to cover even more new applications.”
MLS gaskets consist of multiple layers of stainless steel, sometimes with a special coating to improve their sealing ability, such as nitrile rubber or an elastomer. Depending on the gasket, there will be anywhere from two to about seven layers riveted to a central metal core. These multiple layers are designed to take up the space created by the cylinder head flexing away from the block.
“Cometic MLS, MLX and HP head gaskets are built to handle minor surface irregularities, but need a carefully prepped surface for the best results,” Hale notes. “When installing one, it’s essential to ensure the surface finish of the block and cylinder head is smooth to achieve a proper seal and avoid leaks. We recommend a surface finish of 50 Ra or finer for optimal performance, regardless of the head or block material. As a reminder, always check with the fastener manufacturer for the correct torque values. Proper torque is critical when installing any gasket.”
MLS gaskets require precise surface prep, but also require a certain amount of surface roughness to achieve a good seal. All aftermarket gasket manufacturers will recommend the right Ra number to aim for.
“Our MLS head gaskets are made of fully hardened stainless-steel material, engineered to OEM form, fit, and function,” McCrum says. “With the newest coatings being developed with embossed sealing beads, our gaskets can be adapted to less than perfect surfaces of up to an 80 Ra sealing surface.”
While MLS gaskets continue to be the most popular choice for most engine builds from the low end of the power spectrum through moderately high-powered engines, new technology is helping keep these gaskets on even more builds.
“The newest standard developments which Mahle fully supports include ‘form-in-place’ gaskets, which are produced by chemically binding or injecting the gaskets on a dedicated carrier to ensure proper placement and consistent sealing surface heights,” McCrum says. “Another widely used technology are ‘press-in-place’ gaskets. These are precision-molded gaskets that fit into factory-machined grooves such as the water pump, thermostat housing or other locations that require a precisely placed gasket every time.”
Similarly, the folks at Cometic have found new ways to improve their manufacturing processes while keeping the high-quality standards customers expect.
“Recently, we’ve upgraded our manufacturing capabilities with additional equipment and expanded our tool and die department,” Hale says. “These improvements ensure we can continue to handle custom gasket requests from engine builders with the same integrity we’re known for.”
In order to help seal some of those higher-horsepower engines, many builders may employ o-rings, or what are sometimes known as Top Fuel hoops, along with MLS head gaskets. These rings can be copper or stainless steel, and sit in a machined groove around the outside diameter of the cylinder. When clamped, they are pushed up towards the cylinder head, which can improve the seal. However, if the o-ring is too big, the protrusion is too great, or the o-ring applies pressure in the wrong area of the MLS gasket, it can have the opposite effect and compromise the seal.
Due to a few of those potential failure points, neither Mahle nor Cometic recommend using o-rings or Top Fuel hoops with their MLS gaskets. If you choose to go this route, just know the risks of doing it incorrectly.
Of course, given today’s ever-growing horsepower levels, MLS gaskets can’t seal every engine, so for those extreme high-horsepower applications, copper gaskets are the common weapon. When using copper gaskets, an o-ring needs to be used as well. The protrusion should be about 25% of the diameter of the wire you’re using while the receiver groove should be 75% of the protrusion. To enable the protrusion to fit, the receiver groove will be set to 150% the width of the wire so the gasket can deform and be pushed outwards to lock it into that groove. This requires precise machining, and should be re-machined every time the cylinder head or block surface is machined.
While copper gaskets seal combustion gases well, they do a poor job of sealing fluids. This is why copper gaskets are best suited to high-horsepower drag race engines where the blocks have no coolant.
As mentioned by Micky Hale of Cometic, in any case of sealing a cylinder head to the engine block, you’ll want to ensure you’re torquing the head down properly, and using quality fasteners to do so.
“As horsepower levels continue to increase, so does the demand for better fastener materials,” Hale notes. “Most fastener manufacturers now offer a variety of materials tailored to different performance levels to ensure the head and block interface stays sealed. Using high-quality fasteners is key to achieving optimal performance and reliability. In some cases, it’s not uncommon to see 1,000 horsepower on stock block and head castings. For maximum horsepower, moving to an aftermarket block or head is often the next step, but it all comes down to building the right combination of parts for your specific goals. It’s also essential to make sure machined surfaces are perfectly flat, parallel, and meet the required specs.”
Even when all the right steps have been followed, horsepower, torque and pressure seem to find a way to still mess things up from time to time, so monitoring head gasket seal is critical too. If you get a head gasket failure, you will typically know about it, but not all leaks end in a catastrophic failure, so hopefully you will detect the issue before it gets to that stage.
One option is a pressure sensor on the cooling system, which allows you to data log the pressure and make it easy to tell if any combustion pressure is leaking. The sensor can be paired with a warning on the dash to alert the driver to back off the throttle and avoid further damage. If you run a dry engine with no cooling system, this isn’t an option. That said, at the power levels those engines typically run, catastrophic failure happens quickly.
When pulling your engine apart, there are a couple of things to watch out for. The most likely area for a head gasket to fail is between the studs, so check for burnt areas on either side of the gasket and also on the engine block and cylinder head.
Since every engine and application is different, there are a lot of options to choose from when it comes to head gaskets, cylinder head sealing techniques and technology, so make sure you consult with an engine builder or the gasket manufacturer to know what is right for your engine and application. EB
