Quality over cost when it comes to head gaskets

Premium-quality parts supplier, FAI Automotive, is urging factors and technicians not to cut corners when it comes to head gasket quality, and to ensure correct specification is met to avoid near-certain failure.

As vehicle technicians will be aware, the head gasket on any internal combustion (petrol) engine has two functions. One of these is to maintain a hydraulic and pneumatic seal, keeping the oil, water and combustion gases segregated into their own specific area of the engine.

However, over the past decade, the humble head gasket has evolved into a high specification, high-value operation critical component.

Multi-layered steel (MLS) head gaskets, which are now the preferred head gasket solution on 95 percent of all modern production engines, are well known within the industry.

However, due to ever-reducing exhaust emission controls, OE manufacturers have moved to a single-layer steel (SLS) head gasket.

The benefit of this technology is that it enables the engine to run at a higher compression ratio, which in turn raises the combustion temperature and ultimately results in less CO² being produced.

The challenge has been to make this SLS gasket seal around the cylinder bores, which is where the greatest amount of thermal stress is concentrated.

The solution to this problem has been the development of new technology that utilises very accurate pulse laser welding machines.

These machines fire a laser beam 500 times per second, welding a stainless-steel fire ring to the head gasket. The thickness of which will vary depending on application, but typically measures 0.1 - 0.2mm.

This additional fire ring, albeit very thin, enables enough pressure to be exerted around the cylinder bore, preventing the combustion gases from escaping.

FAI Technical Director, Dominic Moxon, said: “FAI is one of the very few aftermarket gasket suppliers to have this technology available. As each machine can cost upwards of £500,000, it’s a sizeable investment and therefore one that showcases commitment to ensuring the very best products are brought to market, highlighting a quality-driven agenda.”

There has been a similar development in the compression ignition (diesel) engine sector. Although these head gaskets are still using MLS design, the gaskets are getting thinner. And as a result, they are being exposed to greater thermal stress around the fire ring (cylinder bore).

The latest solutions to contain combustion gases in a modern diesel engine, which can reach temperatures of up to 700°C, is cross hatch or to add radial grooves around the bore on the central layer of the head gasket. 

This additional process during the production of the head gasket is costly, as it can only be produced by a dedicated machine and has to be performed as a separate process.

However, the benefit is that these two methods significantly increase the sealing pressure around the cylinder bore. This ensures a long-lasting seal, providing added reliability to the engine.

Moxon added: “With modern engines being far more fuel-efficient, running at higher temperatures and playing more of a part in the combustion cycle, the humble head gasket has become a vital component.

“It is therefore imperative that the correct specification head gasket is fitted, and ‘cheap’ alternatives are not used. To do so would in the long run be false economy, as a head gasket failure would be certain.”

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