Head gasket
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Copper and brass were originally used as head gaskets, followed by asbestos/steel gaskets in the 1950's, and composite metal and impregnated fiber or graphite composites in the 1980's. In the 1990's the Multi-Layer-Steel gasket (MLS) came into widespread use. Most new engines today are designed with MLS gaskets. | Copper and brass were originally used as head gaskets, followed by asbestos/steel gaskets in the 1950's, and composite metal and impregnated fiber or graphite composites in the 1980's. In the 1990's the Multi-Layer-Steel gasket (MLS) came into widespread use. Most new engines today are designed with MLS gaskets. | ||
| − | In MLS gaskets, multiple thin layers of cold-rolled steel are coated with a very thin layer of | + | In MLS gaskets, multiple thin layers of cold-rolled steel are coated with a very thin layer of elastomeric material. The elastomer "micro-seals" the surface imperfections in the metal, and resists gases, oils, coolants, and high combustion temperatures. |
====Copper head gaskets==== | ====Copper head gaskets==== | ||
| − | Copper head gaskets provide the strongest combustion seal which is why they are used in all | + | Copper head gaskets provide the strongest combustion seal which is why they are used in all nitromethane (Top Fuel) and methanol (Blown Alcohol) applications. They're commonly used in high-performance applications where extreme cylinder pressures will be encountered, such as very high static compression ratios on naturally-aspirated motors or where superchargers or turbochargers are used. Copper head gaskets are re-usable, and they do not have to be re-annealed, however since they are made from a flat sheet of copper, they require relatively flat deck surfaces (no more than .002" differential in any direction). Copper head gaskets are quite forgiving of machining imperfections from higher RA (Roughness Average) surfaces or small scratches in the head and deck surfaces since they are made of malleable (soft) copper which conforms readily to surface irregularities under the compressive clamp load of the tightened head bolts. |
To accomplish combustion sealing with standard copper head gaskets, grooves are machined into the block or the head outside of the combustion sealing area to a width that will retain a stainless wire by friction resistance (usually .039" to .040" wide), the depth of the groove is determined by subtracting the desired protrusion (height) of the installed o-ring from the wire diameter. Stainless steel wire (most often .041" diameter) is then seated into the groove by tapping with a soft faced hammer or other interface tool such as plastic or wood (hard faced hammers can cause dents which create combustion leakage paths). It is advisable to begin and end the o-ring nearest a bolt location to take full sealing advantage of increased loading near the bolt upon the joint in the o-ring. Although copper is a relatively soft material, there is a limit to which it can be displaced by an o-ring. Generally speaking, this limit is about 25% of the gasket thickness. For instance, with a 0.032" thick gasket, you would want to limit the height of the o-ring to about 0.008" above the head or deck surface. For an .043" thick head gasket which is the most common thickness, set the o-ring protrusion at 0.010", for an .050" thick gasket about .012", for an 0.062" thick gasket about 0.015" and so forth. If the groove is cut into the head for the wire, a "receiver groove" can be machined into the block. If the groove is cut into the block deck for the wire, then a receiver groove can be machined into the head surface. When the head is bolted to the block, the wire pushes some of the copper up into the receiver groove and makes a very effective seal. However most street / strip applications do not require receiver grooves, receiver grooves are only required on the most extreme racing applications. You'll also need a good sealer around the water passages (K&W Copper Coat is easy to use and easy to find). Copper head gaskets can be re-used several times, simply use a solvent such as brake cleaner to remove any sealant and inspect the area of the gaskets around the combustion seal to insure that there is no 'carbon tracking' which will appear as a shadow on the head gaskets, this is evidence of combustion leaking. If combustion leakage has occurred, the gasket(s) must be replaced. | To accomplish combustion sealing with standard copper head gaskets, grooves are machined into the block or the head outside of the combustion sealing area to a width that will retain a stainless wire by friction resistance (usually .039" to .040" wide), the depth of the groove is determined by subtracting the desired protrusion (height) of the installed o-ring from the wire diameter. Stainless steel wire (most often .041" diameter) is then seated into the groove by tapping with a soft faced hammer or other interface tool such as plastic or wood (hard faced hammers can cause dents which create combustion leakage paths). It is advisable to begin and end the o-ring nearest a bolt location to take full sealing advantage of increased loading near the bolt upon the joint in the o-ring. Although copper is a relatively soft material, there is a limit to which it can be displaced by an o-ring. Generally speaking, this limit is about 25% of the gasket thickness. For instance, with a 0.032" thick gasket, you would want to limit the height of the o-ring to about 0.008" above the head or deck surface. For an .043" thick head gasket which is the most common thickness, set the o-ring protrusion at 0.010", for an .050" thick gasket about .012", for an 0.062" thick gasket about 0.015" and so forth. If the groove is cut into the head for the wire, a "receiver groove" can be machined into the block. If the groove is cut into the block deck for the wire, then a receiver groove can be machined into the head surface. When the head is bolted to the block, the wire pushes some of the copper up into the receiver groove and makes a very effective seal. However most street / strip applications do not require receiver grooves, receiver grooves are only required on the most extreme racing applications. You'll also need a good sealer around the water passages (K&W Copper Coat is easy to use and easy to find). Copper head gaskets can be re-used several times, simply use a solvent such as brake cleaner to remove any sealant and inspect the area of the gaskets around the combustion seal to insure that there is no 'carbon tracking' which will appear as a shadow on the head gaskets, this is evidence of combustion leaking. If combustion leakage has occurred, the gasket(s) must be replaced. | ||
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*Spark plugs with coolant deposits. ''(confirm this, and expand)'' | *Spark plugs with coolant deposits. ''(confirm this, and expand)'' | ||
*Sound of air rushing or whistling coming from cylinder head. You can also listen with a stethoscope. | *Sound of air rushing or whistling coming from cylinder head. You can also listen with a stethoscope. | ||
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*Two adjacent cylinders with low but equal pressure. Indicates head gasket failure between the two cylinders. | *Two adjacent cylinders with low but equal pressure. Indicates head gasket failure between the two cylinders. | ||
*Car misfires or runs rough at low speeds, due to coolant in the combustion chamber. ''(confirm)'' | *Car misfires or runs rough at low speeds, due to coolant in the combustion chamber. ''(confirm)'' | ||
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*[http://www.scegaskets.com/Shop/Control/Product/fp/vpid/6650081/vpcsid/0/SFV/32777 K&W Copper Coat] | *[http://www.scegaskets.com/Shop/Control/Product/fp/vpid/6650081/vpcsid/0/SFV/32777 K&W Copper Coat] | ||
*[http://www.dynatexinc.com/catalog.asp Dynatex Hi-Tack Gasket Spray] | *[http://www.dynatexinc.com/catalog.asp Dynatex Hi-Tack Gasket Spray] | ||
| − | *[http://www. | + | *[http://www.hylomarsealant.com/ Hylomar Universal Blue] |
*[http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Copper_Spray-A-Gasket_Hi-Temp_Adhesive_Sealant.htm Permatex Copper Spray-A-Gasket Hi-Temp Adhesive Sealant] | *[http://www.permatex.com/products/automotive/automotive_gasketing/gasket_sealants/auto_Permatex_Copper_Spray-A-Gasket_Hi-Temp_Adhesive_Sealant.htm Permatex Copper Spray-A-Gasket Hi-Temp Adhesive Sealant] | ||
*[http://permatex.com/products/automotive/automotive_gasketing/gasket_sealants.htm various Permatex gasket sealants] | *[http://permatex.com/products/automotive/automotive_gasketing/gasket_sealants.htm various Permatex gasket sealants] | ||
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Engine additives that claim to repair questionable head gaskets should only be considered a temporary fix, at best. Nevertheless, they may occasionally be used. | Engine additives that claim to repair questionable head gaskets should only be considered a temporary fix, at best. Nevertheless, they may occasionally be used. | ||
| − | Common products include [http://www.barsproducts.com/1100.htm Bar's Leaks head gasket repair], [http://www.rxauto.com/ Thermagasket]and GOSS Chem-i-Weld. Also, sodium silicate (known also as "water glass") can be used, and it's an ingredient in some commercial head gasket repair additives. It can be found at a pharmacy. It is incompatible with antifreeze, thus the system must be emptied before the water glass can be used. Then the system is flushed and the antifreeze replaced. | + | Common products include [http://www.barsproducts.com/1100.htm Bar's Leaks head gasket repair], [http://www.rxauto.com/ Thermagasket]and GOSS Chem-i-Weld. Also, sodium silicate (known also as "water glass") can be used, and it's an ingredient in some commercial head gasket and block/head crack repair additives. It can be found at a pharmacy. It is incompatible with antifreeze, thus the system must be emptied before the water glass can be used. Then the system is flushed and the antifreeze replaced. |
Any "leak stopper" or head gasket "repair additive" should be avoided. Use of such products leads to further engine damage, such as seized or leaking water pumps, clogged water or oil passages, or clogged radiators and thermostats. If you use these products, be aware of possible problems caused by them. | Any "leak stopper" or head gasket "repair additive" should be avoided. Use of such products leads to further engine damage, such as seized or leaking water pumps, clogged water or oil passages, or clogged radiators and thermostats. If you use these products, be aware of possible problems caused by them. | ||
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*Follow specific torque settings and bolt-tightening sequence perfectly. Re-torque as specified. | *Follow specific torque settings and bolt-tightening sequence perfectly. Re-torque as specified. | ||
*Replace both at the same time, even if only one has blown. | *Replace both at the same time, even if only one has blown. | ||
| − | *Oil the tips of the cylinder head bolts with light oil. ''(confirm this, and expand)''. Also, you can use a little bit of oil on the underside of the bolt, to aid getting the proper torque reading. | + | *Oil the tips of the cylinder head bolts with light oil. ''(confirm this, and expand)''. Also, you can use a little bit of oil on the underside of the bolt, to aid getting the proper torque reading. If using aftermarket fasteners, follow the manufacturer's directions for torque and type of lubricant used. |
*Sometimes a sealant will need to be used on the head bolts, as they may intersect the water jackets, and be exposed to engine coolant. Use a non-hardening sealer ''(confirm and expand)''. | *Sometimes a sealant will need to be used on the head bolts, as they may intersect the water jackets, and be exposed to engine coolant. Use a non-hardening sealer ''(confirm and expand)''. | ||
*Change the oil and oil filter too -- they're likely contaminated with coolant. | *Change the oil and oil filter too -- they're likely contaminated with coolant. | ||
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Some head gaskets are re-usable several times and others should never be re-used. Steel shim head gaskets are designed for one use only. Composite or graphite head gaskets are most often not re-usable because of [[rust]] damage to the steel core, disintegration of the surface material or damage or loss of the sealant material. MLS gaskets are most often not re-usable because the elastomeric coating is scubbed off of the combustion and coolant seals by abrasion from temperature induced expansion and contraction. Traditional copper head gaskets are re-usable, Titan and ICS Titan copper head gaskets from SCE are also re-usable. Even if a head gasket is re-usable, many people prefer to use a new one. The labor involved in replacing a head gasket, and the potential for engine damage from a blown gasket are too great to risk. | Some head gaskets are re-usable several times and others should never be re-used. Steel shim head gaskets are designed for one use only. Composite or graphite head gaskets are most often not re-usable because of [[rust]] damage to the steel core, disintegration of the surface material or damage or loss of the sealant material. MLS gaskets are most often not re-usable because the elastomeric coating is scubbed off of the combustion and coolant seals by abrasion from temperature induced expansion and contraction. Traditional copper head gaskets are re-usable, Titan and ICS Titan copper head gaskets from SCE are also re-usable. Even if a head gasket is re-usable, many people prefer to use a new one. The labor involved in replacing a head gasket, and the potential for engine damage from a blown gasket are too great to risk. | ||
| − | When | + | When reusing gaskets, they can be coated with the head gasket sealants listed above in "Head gasket sealants"; traditional copper gaskets can also be sealed with aluminum spray paint available from [http://www.vhtpaint.com/products VHT]. ''(confirm this product name and description)''. |
==Suppliers and manufacturers of head gaskets== | ==Suppliers and manufacturers of head gaskets== | ||
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