Race Pages: What are the differences between head gasket materials, and how do you
pick which type is right for a particular application?
SCE; There are two major groups of head gasket construction (Composite & Metal) with a few sub-sets in each.
1. So called "composite" head gaskets are made several ways;
A. Thin gasket sheeting bonded to a steel core with a fire ring at the cylinder bore and various kinds of coatings to seal fluids.
B. Perforated metal with a compressible core such as flexible graphite again with a coating for sealing and a fire ring around the bores.
C. Perforated metal core with facing material such as flexible graphite mechanically “clinched” to the core and fire rings around the bores.
There are some variations in the construction and materials but those are the major differences. Composite gaskets are “user friendly” in that they require no additional sealants and are capable of sealing less than perfect surfaces due to the overall compressibility and capillary sealing qualities of the facing materials. At SCE we chose the 3rd method of construction for its simplicity and resistance to heat, also in the racing environment additional sealants should not be covering the fire ring as they can eventually burn away and unload the combustion seal.
2. Metal head gaskets which are strongest, consist of several types;
A. Shim steel, the oldest of the pure metal gaskets is simply a thin (.015” to .020”) stamping that is embossed around the openings to achieve load differential. These gaskets require use of a sealant, “back in the day” they were sprayed with silver paint & the tiny flecks of aluminum did the sealing work.
B. Multi layer steel or MLS, this relatively new method of construction consists of two or more embossed stainless sheets riveted to a flat metal core. This method offers some advantages over the shim steel, they are available in different thicknesses so the builder can adjust compression height, and they require no additional sealant due to a micro thin layer of nitrile rubber or flouroelastomer sealant applied to the facings. Due to the hardness of stainless steel MLS gaskets require a very smooth finish surface or leaks may result.
C. Solid copper is the strongest of the metal head gaskets, when used with an o-ring these gaskets control the explosive force of top fuel engines exceeding 15,000psi in the combustion chamber which compares to approximately 1800psi in a pro stock engine. Copper gaskets offer the most options to the engine builder for bore & thickness combinations and the material is malleable allowing it to conform well. Coolant leaks typically associated with copper gaskets are no longer an issue. The new SCE TITAN head gasket is the world's first self sealing copper head gasket offering the racer the best of both worlds, ultimate strength and built in fluid sealing for leak proof performance.
Race Pages: When you're talking about head gaskets, is there such a thing as "too
much" gasket for a particular use, or is it mostly cost issues that keep
everyone from running a high-performance O-ring setup?
SCE; In my opinion you can’t be too safe. The choice of head gasket may be the only limiting factor to performance when good components are used throughout the rest of the engine. If the customer does not intend to better the performance of the car by adding or increasing nitrous, a blower, or turbo charging then a good composite head gasket is sufficient. However, in my experience the nature of our customer is to push the envelope.
Race Pages: What's available in the way of exhaust gaskets, and why would you pick,
say, a copper gasket over a conventional material?
SCE; This and other industries are still suffering the effects of trial lawyers and asbestos so no company big enough to be a target will touch the stuff. Because of that there are now several good non-asbestos alternatives the best being metal reinforced graphite which is what we offer for our upscale composition gasket. Copper exhaust gaskets work well simply because of the properties of the metal, copper conforms to the surfaces being sealed and there are no binders to cook out so the gasket will not shrink from heat cycling and blow out. Copper is also a great heat conductor so an added benefit is that the flange stays the same temperature as the head resulting in less warpage.
Race Pages: Sealant or no sealant: Which gaskets need goo applied to them to work
properly, and why? Also, which sealants do you recommend for the gaskets
that need them?
SCE; As I mentioned above, our Self Sealing TITAN copper head gasket requires no goo, it has precision seals tightly bonded to both sides of the gasket around each coolant and oil passage. The seals are staggered top & bottom rather than stacked allowing the soft copper to conform around the seal as the head is torqued forming a containment trough which locks it in place somewhat like an o-ring groove. This patented design allows the gasket to have metal to metal contact at the o-ring which is critical to sealing the combustion pressures associated with racing.
Conventional copper head gaskets require additional sealant when the engine in question is running coolant. Many people use silicone however there are pitfalls to be avoided when doing so. You don't want the head “riding” on a layer of cured silicone; it won't begin to seal combustion pressure. We recommend a light coat of anaerobic sealer (copper coat, Hylomar) that does not cure so it will push out of where it's not needed and stay where it needs to be.
Races Pages: Any other question you get asked a lot that you'd like to pass along...
Paul, I could go on for pages & pages, I’m kind of a “gasket geek”. Hopefully this will help with your article, thanks again for the opportunity.
Associate Editor, ProMedia Publishing
Head Gasket considerations when adding Nitrous Oxide to an engine.
An item too often overlooked in planning for the addition of power enhancers such as Nitrous Oxide is the cylinder head gaskets that actually seal the resultant higher combustion pressure.Â SCE Gaskets offers two “stages” of performance head gaskets for use in Nitrous applications.
- Stage 1; SCE Pro Seal composite head gaskets. These gaskets utilize a high density flexible graphite body mechanically “clinched” to a steel core, then wrapped with 321 stainless fire ring armor. This combination of base materials and methods of manufacture provide a gasket that is strong enough to seal a 150 to 200HP shot of nitrous while offering unsurpassed protection against heat damage.
- Stage 2; SCE Pro Copper solid copper head gaskets. These are the bad boys of drag racing. When used in conjunction with a stainless steel o-ring and receiver groove SCE Copper gaskets will seal the biggest multi stage nitrous system you can fit between the fenders. Also, SCE now offers the worlds first self sealing copper head gaskets. Just introduced, the SCE TITANâ„¢ self sealing copper head gasket not only seals off-the-scale combustion pressure, it also assures leak-free coolant and oil sealing.
So you see, there are products to make your street driven bottle rocket as dependable as it is quick. It just requires a little planning.
FAQ's (FREQUENTLY ASKED QUESTIONS)
- When using a copper head gasket, do I have to O-Ring my motor?
- SCE always recommends using an O-Ring (SCE part # 31542) and an anaerobic sealer such as Hylomar (SCE part # 81998) or Copper Coat.
- Can I install an O-Ring the head or must it be in the block?
- The o-ring seals equally well in either the block or head, however it is usually easier to install in the block using a boring bar or a manual o-ring cutter.
- Are there any recommendations on how to O-Ring an engine?
- Detailed instructions are available on the Internet @ http:/www.scegaskets.com under Tech Tips. (They are also attached to the end of these questions)
- Are copper head gaskets reusable?
- Yes, they can be reused several times as long as there are no signs of failure, such as carbon tracking beyond the o-ring.
- When installing embossed copper exhaust gaskets, which side goes toward the head?
- The flat side of the embossed copper exhaust gasket faces the head. The embossing allows for any irregularities in the manifold or header.
- Are copper exhaust products reusable?
- Yes, Copper exhaust gaskets can be reused several times as long as they are re-installed on the same flange from which they came.
- Do you recommend a re-torque on head gaskets?
- Yes, since our gaskets live in the extreme conditions found in High Performance engines, SCE recommends a re-torque on all head gaskets.
8. Does SCE have a high performance head gasket other than copper?
- Yes, our Pro-Seal performance head gasket is designed specifically for street/strip or naturally aspirated racing engines.
Tech Tips; Pro-Copper Head Gaskets
- WHEN IS A PERFORMANCE HEAD GASKET NECESSARY?
- Whenever cylinder pressure is substantially increased, usually as a result of performance enhancing modifications. In our conversations with customers we've heard the same numbers repeated quite often. Over 8 pounds boost, or over 150hp of nitrous oxide.
- WHAT TYPE OF HEAD GASKET IS RECOMENDED?
- SCE manufactures the full range of performance head gaskets, from our Pro-Seal composite for moderate performance increases such as Street blowers or 150hp nitrous kits, all the way to our Pro-Copper head gaskets which provide superior sealing in extreme conditions.
3. REASONS FOR CHOOSING A COPPER HEAD GASKET.
- Extreme performance enhancing modifications; 15:1 or higher compression ratios, high levels of boost, or nitrous kits exceeding 200hp.
- Piston to head clearance adjustments. If for example, @ TDC, the piston and rod assembly is too close to the head, a thicker head gasket can restore the proper clearances. SCE copper head gaskets are available as thick as .093”.
- Compression ratio adjustments can be made by using thicker or thinner gaskets. However, reason must be used when adjusting compression ratios with gasket thickness, as every .010” change in thickness will net a change in volume of about 2.5cc. This method will never raise an 8.5:1 street engine to a 12.5:1 race engine but small adjustments are possible.
- BENEFITS OF COPPER HEAD GASKETS
- Conductivity. Copper is the standard by which all other conductors are measured, therefore a copper gasket provides superior thermal conductivity, acting to stabilize head and block temperatures which makes tuning easier.
- 25% coefficient of elasticity. One of the properties of copper is that it stretches before a catastrophic failure, thereby providing an extra measure of safety in case of severe detonation.
- Strength. Copper (in the form we use) has a tensile strength of approximately 32,000 psi, compare this to the 1,200 to 1,800psi tensile strength of most facing materials used on conventional performance head gaskets.
- Clean flat surfaces are essential to seal any performance engine. A solvent such as brake cleaner should be used on the block and head prior to assembly.
- O-rings are generally required to make a copper gasket system work to potential. SCE sells stainless steel O-ring wire in a kit to do one V-8 engine or spools for the engine builder. SCE stainless steel O-ring wire is preferred over copper wire that can flatten or dentÂ to form a leak path.
- O-ring grooves may be cut in either the block or cylinder head. When using copper head gaskets thinner than .050”, O-ring height should be no more than 25% of gasket thickness. For instance, the proper dimensions for an .043” thick gasket using .041” wire would be; a .038” to .040” groove width (provides a .001” interference fit), and a .032” groove depth (leaves .008”-.010” of the wire protruding above the deck). This machining can be done at most high performance machine shops
- When receiver grooves are necessary, alignment of O-ring and receiver groove is critical, as is the depth and width of the receiver groove. Generally receiver groove depth should be 75% of the O-ring protrusion and the receiver groove should be 1.5 times the wire width. Example: If the O-ring is .041” wide and .015” above the deck; receiver groove should be .012” deep and .060” wide.
- While the machining of O-ring and receiver grooves must be done by a machinist, the installation of the O-ring wire can be done by anyone, using common hand tools. When tapping O-ring wire into the groove, use care to avoid denting the wire. SCE provides an O-ring installation kit, (SCE PART #31542) which includes instructions, an installation tool and O-ring wire. When cutting stainless O-ring wire, file the ends square to provide the tightest possible seal.
- Head gaskets should be re-torqued after initial run-in regardless of type, solid copper or composition. SCE recommends using factory torque specs. Do not over torque. Allow the heads and block to cool for accurate torque readings. Always use a torque wrench and have it calibrated often. Premium grade head bolts or studs, with hardened washers are recommended.
- SCE copper gaskets can be reused 4 to 5 times simply by cleaning in common solvent. DO NOT use a torch or household oven to “re-anneal” copper gaskets. The annealing process requires special vacuum ovens to achieve satisfactory results.
These installation tips may seem like a lot of information for head gaskets, however, installing a copper head gasket and O-ring system is really easier than degreeing a cam, and just as important.