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When you browse the internet for car parts – high performance or otherwise, you’ll soon discover the choice for many parts proves pretty much cosmic. Gaskets are no different. And in today’s world, gasket technology has evolved rapidly. Consider the head gasket: Where many older engines were manufactured with as many as a half dozen cylinder head bolts surrounding each cylinder, today’s engines are often built with a maximum of four. That means the head gasket has a larger responsibility. Much of that technology has filtered down toward the high performance community. Technology for many gaskets is a lot different than it was even a few short years ago. Some of this resulted in new types of gaskets (MLS or “Multi Layered Steel” is one example). But in other cases, it allowed companies to refine existing gaskets. Some of what you see below might prove to be a wee bit surprising. In addition, some of the practices used to install gaskets have changed. Let’s start at the beginning:
When Chevrolet first started using aluminum heads on production cars (they were one of the first in North America), a need developed for some form of composition head gasket. Standard equipment on those early L88’s and L89’s was a composition gasket (typically made by Victor). Mostly, they started as a metal core with a pliable material such as asbestos applied to both sides. As you can well imagine, Asbestos wasn’t a hot ticket. Still, the concept for a gasket remained the same: Make use of a material that can easily conform to block and cylinder head imperfections and at the same time incorporate a flange or “fire ring” around the cylinder bore opening. This was done to contain cylinder pressure. A sealant was (is) often applied around the coolant and oil passages within the gasket. In the end, the fire ring or flange was (and still is) a separate piece that locked in position within the gasket.
A big problem with the old one-piece steel head gaskets or the early composition gaskets was the fact they mandated a hot retorque (where the engine was cycled to operating temperature and then the head bolts or studs were retorqued). It doesn’t seem like such a big job until you realize things like the headers had to be removed for many applications, simply because they covered up the bottom row of head bolts. In some cases, just removing the headers can prove to be nightmarish. Plus, other components in the engine compartment simply get in the way, making the torqueing process challenging.
What ended all of this was Fel-Pro’s “PermaTorque®” innovation. Fel-Pro came up with a head gasket line up that not only sealed perfectly, it also eliminated the need for a retorque of any sort.
Those gaskets became the most popular race-winning head gaskets on the planet (and they still are today, hence the information presented here). According to Fel-Pro: “The key difference between traditional passenger car head gaskets and our Fel-Pro Performance head gaskets is the wire ring combustion seal. Inserted within a stainless steel armor surrounding each cylinder, the wire ring design provides highly concentrated sealing around the combustion chamber. The pre-flattened wire ring raises combustion sealing force to roughly three times that of standard head gaskets. In addition, the armor is 321 series stainless steel, and can withstand combustion pressures ranging from 1500 to 3000 psi. Gaskets are available with either pre-flattened copper or steel wire rings.”
“These head gaskets include a rubber/fiber facing material reinforced with KEVLAR® fiber, laminated to a solid steel core to resist torque loss and seal fluids. Conformable anti-stick coatings are used on the gasket body to help seal minor surface irregularities. Besides aiding in micro-sealing, these surface coatings make gasket removal and clean-up easier. This is a special advantage in performance applications, where engine changes and maintenance require frequent disassembly.”
“Fel-Pro racing head gaskets are installed dry – sealers are neither required nor recommended. These gaskets have performed flawlessly in engines at well over 1000 horsepower. They are an ideal solution for most street performance and race engines, and are available “off the shelf” everywhere at a very reasonable cost.”
There’s another big advantage too: It’s the sheer number of thicknesses and bore sizes available from Fel-Pro. Fel-Pro notes that by using a thicker-than-stock head gasket, it can prove to be a low cost solution to reduce the compression ratio or to increase piston to valve clearance or to piston to head clearance. Of course, they’re right.
Before going any further, let’s take a short detour here and consider compressed gasket thickness: Compressed thickness of a gasket is the measurement of the gasket once it has been installed and torqued (compressed) to specification. It is not the thickness of the gasket as you receive it from the manufacturer.
When it comes to compression ratio, compressed gasket thickness has an effect and so does the cylinder head gasket bore. The bigger the compressed thickness of the head gasket, the lower the compression ratio. The bigger the gasket bore, the lower the compression ratio. There are limits you can get away with. For example, the piston to deck clearance must be established for a given application is operate properly (you really don’t want to be whacking the cylinder head with the piston), and at the same time, the need for quench in many engine combinations must also be taken into consideration. If the gasket bore is too small for the cylinder bore, it won’t work. But if the bore is too large, you’re throwing away compression.
In an upcoming issue, we’ll complete our look at Fel-Pro head gasket technology. What we’ll delve into is how to properly install them. Additionally, we’ll also explore other gaskets in the mix, beginning with examples for intake manifolds. In the meantime, check out the accompanying photos:
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