1. Properties of Copper
As we know, Copper is an excellent conductor of heat, in fact it is the standard by which all conductors are measured. Superior conductivity gives the racer the ability to tune better because the head & block are a more even temperature than in the case of either a composite gasket or an MLS gasket which, though it is metal, has a coating of sealant (.001” Viton) that acts as an insulator. Copper has other properties that make it a very suitable choice for head gasket sealing, the tensile strength of copper in the alloy we use is approximately 32,000psi, compared to a tensile strength of 1250psi in the facing material of conventional composite head gaskets. Copper has a 25% coefficient of elasticity; this allows a copper gasket to stretch considerably before failing. This beneficial property has permitted many SCE customers to finish a race event, only to find upon servicing the engine thereafter that the head gaskets had ”pushed” but not failed, the copper body gasket allowed them to finish the event and pointed them to a tuning issue as well.
2. Surface Finish
MLS gaskets require sealing surface finishes much finer than the ICS or a conventional composite head gasket. Fel-Pro recommends 15 to 30 Ra surface finish for their MLS gaskets, to give you a visual, crankshaft journals are finished to about a 12Ra, so, for proper installation of an MLS head gasket you will see your reflection in the sealing surfaces. One reason MLS gaskets require such smooth surfaces is that the gasket layers are made of stainless steel, which is harder than either the block or head, thus the gasket will not conform to irregularities. Further, the sealant coating is only .001” thick which is not sufficient to seal leak paths under the gasket formed by standard head surfacing of 60Ra. Ra stands for roughness average and it is measured in microns or “millionths of a meter”, a surface finish with a roughness average of 60 will have peaks and valleys of .002362” whereas the much finer surface finishes of 15 to 30 Ra will have peaks and valleys of .000590” and .001181” respectively. As one can see from these figures, MLS gaskets would leak fluids on a standard “out of the box” cylinder head surface finish of 60Ra. In addition the normal surface finish will quickly abrade or “scuff” the black fluoroelastomer (Viton) sealant coating on the MLS gasket exacerbating the fluid leak problem. Many machine shops do not have the equipment necessary to produce the surface finish required for MLS head gaskets; the venerable Storm-Vulcan requires a retrofit feed which slows the travel to produce these finishes. Bottom line; ICS requires no special surface finishes, rather, those found on new parts out of the box or easily produced by standard equipment are well within the preferred range, the ICS is easier to use.
3. Combustion Seal
The patented combustion seal in the ICS is a “two stage” dynamic seal; the first stage of sealing is due to load concentration from the wire inserted into the gasket around the bore. This has much the same effect as installing an o-ring in the block or head, it simply creates a load differential under the tightening head bolts. Secondly, the upper & lower flanges of the ICS remain open to combustion pressure to form a gas seal upon which high pressure gases are allowed to act against the opposing flanges of the seal forcing the flanges to remain in contact with the sealing surfaces as shown in the center diagram below. This action of the ICS seal was proven in our initial testing and in subsequent engine builds where extreme combustion pressure (over 3000psi) has been achieved. The ICS head gasket has been proven to outperform the competitors’ gaskets in head-to-head leak down testing where the competing MLS gaskets regularly leak 8% and the ICS head gasket leaks less than 1% in the worst case. In addition, the gasket body of the ICS is one, solid piece of metal, not multiple layers. The one piece metal body and seal construction of the ICS head gasket traps combustion gases in the cylinder. The unique construction of the ICS prevents combustion pressure from escaping, whereas MLS gaskets allow combustion gases to migrate between the layers of the gasket in those cases where clamp load is relieved from cylinder head lifting under extreme combustion pressure.
ICS head gaskets have no sealant on the combustion seal. Metal-to-metal combustion sealing is a subtle but important factor in high compression racing engines. An examination of MLS head gaskets prior to installation reveals that the flouroelastomer sealant coating covers the entire gasket body as well as the combustion seal area. Properly constructed MLS head gaskets have a more pronounced embossment at the combustion seal than at other areas of the gasket body where a less aggressive embossment will suffice for low pressure fluid sealing. Sealant coating around the bores has a tendency to scrub off the more aggressive embossment of the combustion seal the as seen in the lower photo. The result after a relatively short period of run time is a gasket that, in effect, is .002” thinner in the combustion seal area than the rest of the gasket body due to the loss of sealant coating on the combustion seal of the MLS head gasket. The loss of sealant coating on the combustion seal of MLS head gaskets is accelerated by, and is most detrimental in cases such as the small block Chevrolet where two exhaust valves are side by side causing a build up of heat in the center of the cylinder head.
5. Less Damage
MLS gaskets can severely damage cylinder heads when combustion leaks occur due to the fact that stainless has a much higher melting point than aluminum. As seen in the accompanying photos, the cylinder heads were severely damaged by superheated combustion gases leaking between the bores, the head gaskets subsequently melted as well. The application in these photos is a small block Ford on nitrous. This was the result from the first outing after the customer was convinced to try the Com***c MLS gaskets after successfully using SCE copper head gaskets for several years prior. He is once again a satisfied SCE customer. Conversely, when combustion leaks do occur in the ICS, the conductive copper body dissipates heat quickly enough that the cylinder head is spared, or in extreme cases the softer copper gasket body becomes the sacrificial metal, once again saving the much more expensive cylinder head from costly damage.