Do not use any type of adhesive or sealer on gaskets such as the Ultra Seal head gaskets. The special coatings used on the gaskets are more than adequate to properly seal all fluid passages and minor surface imperfections. Attaching proper clamp load is one of the most important steps to a successful seal. After installing the head gasket along with the cylinder head, tighten bolts/studs following engine manufacturer's recommended torque sequence. Tighten in at least three equal steps moving the torque wrench in a smooth, even pull, which will yield the most accurate torque readings. The use of hardened head bolt washers will further reduce friction and increase torque accuracy.
Rubber Coated Embossed Steel Shim: This is a relatively recent head gasket development. Originally the brainchild of Mark Adelizzi when he worked at Fel Pro, this configuration takes an old-fashioned steel shim head gasket and bonds a very thin rubber coating to the surface. In specific locations, multiple layers of this rubber coated steel shim are incorporated. Generally speaking, the rubber coating protects the steel shim core and helps to seal minor surface imperfections. Rubber coated embossed steel shim head gaskets (commonly called "RCE" gaskets) also provide excellent torque retention. Typically, these gaskets are designed for use on very smooth surfaces (usually a micro inch finish of 30 RMS or less).
Copper: According to Clark Copper Head Gaskets, the primary advantage of copper gaskets is the fact they can be built in a variety of uncommon dimensions. For example, Clark can build gaskets in 0.005-inch thickness increments and offers countless off-the-shelf and custom designs unavailable elsewhere. Further to this, copper head gaskets do not compress after the cylinder heads have been torqued to specification. They do not require a hot retorque, but keep in mind these gaskets must be used in an application where either the cylinder head or the cylinder block has been machined for o-rings. In addition, copper head gaskets mandate silicone is used around each water hole in the respective deck surfaces. Copper head gaskets are unique in the fact they can be reused, but remember, you have to scrupulously clean the block and head deck surfaces as well as the gasket itself. According to Clark, these gaskets are most often used in blown, nitrous, or extreme compression ratio applications.
Rubber Coated Copper: Flat Out Gaskets offers a rubber coated copper head gasket. It’s a relatively new development, and similar in concept and performance to the rubber coated embossed steel shim gasket described above. Flat Out Gasket’s Adelizzi points out that when a manufacturer obtains copper from a mill, it is typically very smooth. It looks nice, but it’s tough to get a rubber material to bond to it. By incorporating a proprietary manufacturing process, Flat Out Gaskets is able to successfully bond rubber to a copper head gasket base. What this gasket does is to seal without add on chemicals. And like a conventional copper head gasket, the rubber-coated jobs can be reused (up to three times according to Adelizzi). Flat Out Gaskets notes that if there is damage to the rubber, you can accomplish minor repairs with simple RTV sealants.
Use Them Once And Throw Them Away?
Aside from copper materials, whenever you reuse a gasket (head gasket or any other gasket), you run the risk of premature gasket failure. Why? Simple. When a new gasket is installed, it conforms to the irregularities found on the sealing surfaces (see below) when compressed. Regardless of the type of gasket material used, the gasket is permanently compressed (this of course, is with the exception of a copper head gasket). Typically, this is called "taking a set".
If the gasket is re-used, it is almost impossible to reinstall it in the position it was originally installed in. Since the material has already been compressed, it cannot "readjust" to the sealing surface irregularities. The result? A gasket failure and of course, a leak.
Gasket Mating Surfaces: No matter how good the machine shop, how accurate the machinist or how expensive the equipment, there will always be irregularities in the various mating surfaces. That's why gaskets are required. We should point out that a surface could actually be too smooth. If it is, then the gasket cannot grip the surface. If the surface is too rough, even the best gasket in the world cannot seal the irregularities. Fel Pro states that a surface micro finish of 60-80 RA is preferred for most conventional head gasket applications.
