Cylinder Head Sealing 101: Head Gaskets, Spacers, O-Ringing and Fire Ringing

Head Gaskets

Head Gaskets are one of the most overlooked and inexpensive components to buy when building a performance street or race engine, yet are easily one of the most important. Head gaskets are responsible for containing millions of explosions during their lifetime, compensating for the expansion and contraction of dissimilar metals, and resisting decay from exposure to chemicals and extreme temperatures.

When you increase the compression or boost of your engine setup for increased performance, cylinder pressure increases exponentially. This increased cylinder pressure puts strain on the components that are in charge of sealing the cylinder head to the engine block, including the head gasket. This is why traditional gaskets, made out of softer materials and composites, are prone to ‘blowing out’ of high performance engines.

This leaves the engine builder three main options when choosing a head gasket for performance applications: Multi-Layered Steel (MLS), Cut-Ring (also known as ‘Cooper Ring’), or Copper. Read on to learn more about each:

MLS Head Gaskets

Recommended Applications: Within Factory-Spec and Naturally Aspirated

Today, most engines are assembled with MLS Gaskets from factory as they are made of more durable materials and seal better than traditional composite gaskets. MLS Gaskets allow for load distribution to saturate across the sealing area evenly and reduce bore distortion. The embossments that you notice on the gasket are also designed to enhance sealing once the cylinder head is torqued into place on the engine block.

5150 AutoSport recommends and carries Cometic Mutli-Layered Steel Head Gaskets. Cometic Gasket is a leading worldwide supplier of gaskets and engine sealing solutions for the Automotive Performance, Powersports, Original Equipment and Remanufactured Engine Industries.

Cometic MLS Gaskets are composed of multiple embossed layers of both proprietary, high-temperature coated and uncoated stainless steel. The specialized coating used on Cometic Gaskets conforms to the surfaces of the cylinder head and engine block on the first heat cycle, creating a chemical bond.

Cometic MLS Gaskets are composed of multiple layers of stainless steel. The number of layers used vary by application. Additional layers increase active seal height and can be used to fine-tune compression. MLS Gaskets protect against blow-out because the embossed layers act as a spring.

The number of layers used in the construction of the gasket varies based on the application. Additional layers increase active seal height and can be used to fine-tune compression. MLS Gaskets are able to prevent blow-outs in engines with high cylinder pressure because the embossed layers act as a ‘spring’ and compensate for increased head lift. 

Cut Ring Head Gaskets

Recommended Applications: Turbo-Conversions and Increased Boost

Cut Ring Gaskets consist of stainless steel cut rings and a pliable, perforated metal-core composite gasket. The stainless steel rings bite into the cylinder head under clamp load to form a positive barrier against combustion pressure leaks while the gasket effectively seals coolant and air.

The stainless steel rings on the SCE Gasket bite into the cylinder head under clamp load to form a positive barrier against combustion pressure leaks while the gasket effectively seals coolant and air.

5150 recommends and carries SCE Gaskets’ Vulcan Cut-Ring Head Gaskets. SCE Gaskets were developed as a response to the need for gaskets that can maintain seal under high-pressure applications. 

SCE’s gasket features a special polymer coating and silicone beading to improve sealing around water and air passages. Their stainless rings feature micro-ridges that bite into the cylinder to eliminate movement at the most critical sealing points. The combination of these two elements make for excellent sealing properties without the need for additional sealants.

Copper Head Gaskets

Recommended Applications: With O-Rings, Ultra High-Boost Turbo

Copper Head Gaskets have been used in competition engines for decades, and when combined with steel O-Rings, have proven themselves where other gaskets have failed. Made from 99% Pure Copper, these gaskets feature bead seal on both sides to ensure proper water jacket sealing. It is important to note that these are not a drop-in component; unlike MLS and Cut Ring Head Gaskets, Copper Head Gaskets require a skillful machine shop capable of installing O-Rings into the block or cylinder head to ensure proper sealing. 

Copper Head Gaskets can be installed in engines with or without a receiver groove. For Ultra High-Boost Applications, a receiver groove is recommended.

As the cylinder head is clamped down onto the engine block, the Copper Head Gasket conforms to the O-Ring in the cylinder Head or Block to form a secure seal around the combustion chamber. 

Choosing Your Head Gasket

Not sure which gasket is best for your application? Contact our sales team with the details of your build and one of our dedicated engine build advisors will assist you with selecting the correct sealing configuration for your engine.

Notes on Replacing Head Gaskets

The mating surfaces of your cylinder head and engine block must be professionally smoothed and straightened by a machine shop prior to installing a new head gasket. Metal gaskets are not able to compensate for imperfections the same way that softer gaskets do, and will not mate correctly with an uneven surface.

Upgrading your hardware is a must when reassembling a performance engine. While metal gaskets are able to handle much greater cylinder pressure than softer gaskets, the other components responsible for sealing the cylinder head are also under increased strain. We highly recommend ARP Hardware.

Ringing 

In addition to a performance head gasket, engine builders may choose to have the cylinder head and/or engine block O-Ringed or Fire Ringed in ultra-high performance builds that are generating intense cylinder pressure. These are both processes in which the cylinder head and/or engine block are machined, and wire rings are installed into the surface to provide an additional barrier for sealing the combustion chamber.

O-Ringing

O-Ringing is a process in which a narrow, circular groove is machined into the cylinder head surface, and a circular wire is then pressed into the groove, protruding slightly from the cylinder head surface. When the cylinder head is reinstalled onto the engine block, the O-Ring wire puts additional pressure on the steel ring in the head gasket, creating an improved head-to-block combustion seal.

Fire Ringing

Fire Ringing is similar to O-Ringing but provides a more dependable, stronger seal. It is a process that occurs when a circular groove is machined into the cylinder head and/or engine block surface, depending on the engine and demands of the build. Once the groove is cut, a circular ring is set into the cut grooves. When the cylinder head is torqued back down onto the engine block, these rings crush, creating a strong seal around the combustion chamber. 

Choosing O-Ring vs Fire Ring

In order to best determine the ringing method for your engine, your engine builder will look at the build as a whole. The factors that they will consider are things like boost, fasteners, cylinder pressure, what fluids need to be sealed, and so on.

There is no hard and fast rule for knowing which ringing method is best for your build, which is why it is necessary to work closely with an experienced engine builder.

If you still have questions or would like to discuss your build, contact our knowledgeable engine build advisors with the details of your build and the proper steps to preparing your engine for high performance and high power applications.