Head gasket
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| − | + | , and can be detected with certain techniques. Left unfixed, a blown head gasket could cause severe engine damage. Many symptoms of a bad head gasket are not apparent until the problem is very bad, including the ones listed later in this article. | |
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| − | + | Various different types of head gaskets exist today, for different applications. Care must be taken in removal of the old gasket, selection of a new gasket and proper installation of the new gasket. | |
| − | + | [[Image:Head gasket ford 298-302.jpg|thumb|left|220px|Head gasket Ford 289 - 302 CID]]<br style="clear:both"/> | |
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| − | Various different types of head gaskets exist today, for different applications. Care must be taken in removal of the old gasket, selection of a new gasket and proper installation of the new gasket. | + | |
==Head gasket basics== | ==Head gasket basics== | ||
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===Different types of head gaskets=== | ===Different types of head gaskets=== | ||
| − | Copper and brass were originally used as head gaskets, followed by asbestos/steel gaskets in the | + | Copper and brass were originally used as head gaskets, followed by asbestos/steel gaskets in the 1950s, and composite metal and impregnated fiber or graphite composites in the 1980s. In the 1990s 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 elastomeric material. The elastomer "micro-seals" the surface imperfections in the metal, and resists gases, oils, coolants, and high combustion temperatures. | 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. | ||
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====Copper head gaskets==== | ====Copper head gaskets==== | ||
| − | 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 | + | 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 fasteners. |
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| + | ===O-ring sealing=== | ||
| + | [[File:O-ringdrawing.jpg|thumb|right|450px|O-ring diagram]] | ||
| + | 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, 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 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. <br style="clear:both"/> | ||
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| + | 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 0.043" thick head gasket which is the most common thickness, set the o-ring protrusion at 0.010", for an 0.050" thick gasket about 0.012", 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 acetone, carb cleaner, or 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. | |
| + | Gasket Works makes a stainless steel O-ring that is only 0.004" thick and eliminates the need to groove the block or head. See more [http://www.headgasket.com/images/olympic%20rings.jpg here]. | ||
=====Modern copper head gaskets===== | =====Modern copper head gaskets===== | ||
| − | SCE Gaskets makes copper head | + | There are several manufacturers of copper head gaskets. Copper gaskets come in many thicknesses, and in most cases are reusable. Among them is [http://www.scegaskets.com/page/sitemap.html SCE Gaskets], who makes the Titan ICS (Integral Combustion Seal) copper head gasket with coolant and oil passage seals bonded to the sealing surfaces of the head gasket. These built-in seals eliminate the need for additional sealants. These head gaskets are installed dry and there are two versions available: one for engines with machined O-ring combustion seals and one for those without O-rings. The copper head gasket offered by SCE for engines without machined O-rings includes both coolant seals and and the Integral Combustion Seal which eliminates the need to have O-ring grooves machined into the block or heads. These head gaskets allow engine builders to exploit the benefits of of copper, such as the wide range of thicknesses, superior strength, superior combustion sealing, conformability to deck surfaces and superior heat conductivity, with none of the prior disadvantages of 'old fashioned' copper head gaskets. |
| − | + | [[File:Sce titan cu hg.jpg|thumb|300px|left|SCE ICS copper head gasket with silicone sealing beads]] <br style="clear:both"/> | |
| − | ====Steel | + | ====Steel shim head gaskets==== |
| − | Steel shim gaskets | + | Steel shim head gaskets are exactly what the name implies, simply a thin sheet of embossed steel with no sealers applied. Steel shim gaskets rely on the combination of increased localized pressure from the embossing (stamped ridges) much like MLS head gaskets, with the addition of a user applied sealant to insure liquid tight operation. |
| + | Steel shim gaskets come in a variety of thicknesses as the name implies and range from 0.010" up to 0.080". Originally, the gaskets were of flat steel sheeting and went on to have an embossed surface. The embossing was strategically placed on the gasket surface around cylinder holes, water inlets, and outer surfaces. The embossing provided extra metal to fill in voids over the sealing surface when torqued into place. Shim gaskets could raise or lower compression in an engine without machining. They were the front runners of the now used fiber and non-ferrous metal gaskets. | ||
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| + | The term "blowing a gasket" was common for racers because they were using a very thin 0.010" or 0.020" compressed thickness steel shim head gasket to raise compression. Because of its thinness, the gasket could fail allowing leakage between adjacent cylinders, aka "blowing a head gasket". The vehicle could only remain running for as long as the coolant held out or until some other mode of failure took the engine out of contention. Engine builders of the day were often seen applying a couple coats of aluminum or copper paint to both sides of head gaskets to make them stick in place and seal the mating surfaces. The metallic particles in the paint would fill in the small voids and irregularities in the machined deck surfaces of the heads and block. | ||
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| + | ====MLS head gaskets==== | ||
| + | [[File:Mls felpro hg.jpg|thumb|400px|Felpro MLS head gasket showing the layers]] | ||
| + | Be sure to consult the manufacturer's recommendations concerning surface preparation, sealers, and application. | ||
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| + | Sealant use may be required when retrofitting MLS (multi-layer steel) head gaskets to engines which were not originally produced with MLS head gaskets, or when using MLS head gaskets on engines that have not been properly prepared. For proper coolant, oil, and combustion sealing, MLS head gaskets require surface finishes of 30 RA (Roughness Average) or finer, this is because the elastomeric coating on the sealing surfaces of MLS head gaskets is approximately .001" thick which is too thin to seal leak paths in the peaks and valleys of rougher (RA30+) finishes. | ||
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| + | Cometic has a 'Phuzion' head gasket that "combines MLS tech with a gas-filled, aerospace-alloy O-ring for ultimate head sealing" without special block mods. <br style="clear:both"/> | ||
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| + | ====Graphite head gasket==== | ||
| + | Graphite head gaskets can be used on aluminum heads with an iron block (they work equally well with iron heads on an iron block). Graphite is excellent in handling high temperatures and is anisotropic (draws heat away from hot spots). It also seals very well too. Some drawbacks to using graphite is that it cannot withstand exposure to oil over a long period of time, can be crushed and extruded, and it also leaves a coating on the block and heads that is harder to remove than traditional head gaskets. | ||
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| + | An article that mentions graphite gasket technology is '''[http://www.enginebuildermag.com/Article/2585/gasket_technology_the_science_of_sealing.aspx here]'''. | ||
===Aluminum cylinder heads=== | ===Aluminum cylinder heads=== | ||
| − | Though aluminum is lighter than cast iron, it expands | + | Though aluminum is lighter than cast iron, it expands twice as fast. This quicker cycle of expansion and contraction stresses head gaskets. To handle this, a non-stick coating is often applied to the gasket, like Teflon or molybdenum. |
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| + | Many OEMs are using graphite head gaskets on iron blocks with aluminum heads to help compensate for different coefficients of expansion between the two differing metals. Graphite head gaskets may have multiple types of coatings in different areas to facilitate sealing (silicone) and expansion (Teflon/molybdenum). | ||
With iron heads, a product can be applied for the opposite effect. Silicone, Viton, or other fluoroelastomer sealants are applied to '''increase''' the pressure between the iron heads and the iron block. | With iron heads, a product can be applied for the opposite effect. Silicone, Viton, or other fluoroelastomer sealants are applied to '''increase''' the pressure between the iron heads and the iron block. | ||
=="Blown" head gaskets== | =="Blown" head gaskets== | ||
| + | {| | ||
| + | |[[File:Morris Marina Blown head gasket.jpg|360px]] | ||
| + | |[[File:Boosted pontiac 400 engine+blown head gasket.jpg|350px]] | ||
| + | |[[File:Blown into cooling.jpg|350px]] | ||
| + | |} | ||
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===Reasons why head gaskets fail=== | ===Reasons why head gaskets fail=== | ||
| − | *Overheating, possibly from a blown hose, water pump, or thermostat | + | *Too much outward pressure that overcomes the clamping force of the head to the block |
| − | *Engine pre-ignition or detonation | + | *Overheating, possibly from a blown hose, water pump, or thermostat |
| − | *Improperly torqued cylinder head | + | *Engine pre-ignition or detonation |
| − | *Faulty cylinder head bolts | + | *Improperly torqued cylinder head |
| − | *Some blocks are more prone to head gasket failure, because the bolt positioning applies uneven pressure or there are too few bolts surrounding the cylinder | + | *Faulty cylinder head bolts |
| − | *Stretched cylinder head bolts | + | *Some blocks are more prone to head gasket failure, because the bolt positioning applies uneven pressure or there are too few bolts surrounding the cylinder |
| + | *Stretched cylinder head bolts | ||
| + | *Reusing torque to yield fasteners | ||
===Symptoms of a blown head gasket=== | ===Symptoms of a blown head gasket=== | ||
| − | Some of the symptoms below may also indicate a cracked cylinder head. | + | Some of the symptoms below may also indicate a cracked block or cylinder head. |
| − | *Foaming or bubbling coolant. Indicates head gasket has failed between a cylinder and a passage in the water jacket | + | *Foaming or bubbling coolant. Indicates head gasket has failed between a cylinder and a passage in the water jacket |
| − | *Rapid pressure buildup in cooling system, before engine is warm. Or, cooling system appears to be malfunctioning | + | *Rapid pressure buildup in cooling system, before engine is warm. Or, cooling system appears to be malfunctioning |
| − | *Radiator frequently gets low on water (it could be being discharged through the tailpipe) | + | *Radiator frequently gets low on water (it could be being discharged through the tailpipe) |
| − | *White smoke in exhaust, or sweet smelling exhaust | + | *White smoke in exhaust, or sweet smelling exhaust |
| − | *"Milkshake" oil, caused by coolant in oil | + | *"Milkshake" oil, caused by coolant in oil |
| − | *Oil in coolant, causing foaming in coolant | + | *Oil in coolant, causing foaming in coolant |
| − | *Oil or coolant leaking | + | *Oil or coolant leaking into combustion chamber |
| − | *Low cylinder pressure. | + | *Low cylinder pressure, especially on adjacent cylinders |
| − | *Milky-gray ring around the oil cap | + | *Two adjacent cylinders with low but equal pressure. Indicates head gasket failure between the two cylinders |
| − | *Drops of coolant coming | + | *Milky-gray ring around the oil cap caused by coolant mixed into the motor oil |
| − | *Spark plugs with coolant deposits | + | *Drops of coolant coming from the exhaust |
| − | *Sound of air rushing or whistling coming from cylinder head. You can also listen with a stethoscope | + | *Spark plugs with coolant deposits- "steam cleaned" look, greenish/yellowish/orange deposits |
| − | + | *Sound of air rushing or whistling coming from cylinder head. You can also listen with a stethoscope | |
| − | + | *A test kit indicates combustion by-products in the coolant | |
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| − | *A test kit indicates combustion by-products in the coolant | + | |
===Compression testing and leak down testing=== | ===Compression testing and leak down testing=== | ||
| − | *If a compression test shows two cylinders with equal but low compression, | + | *If a compression test shows two cylinders with equal but low compression, that may indicate a blown head gasket, with a leak between those two cylinders. |
| − | * | + | *Do a leak down test. |
| − | * | + | *Pressure test the coolant system. If you pressurize the system, and you lose pressure, you may have a blown head gasket. |
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| + | ==How to choose a head gasket== | ||
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| + | ===Quench vs. head gasket thickness=== | ||
| + | The head gasket thickness depends on the desired quench measurement and desired compression ratio. Piston to valve clearance must be verified. | ||
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| + | Although static compression ratio should be determined by the piston configuration and the volume of the combustion chamber, small compression ratio adjustments are possible by altering gasket thickness as long as this doesn't cause the '''[[quench]]''' (or "squish") dimension (piston crown to under side of cylinder head with the piston at TDC) to be out of spec. Generally speaking, this figure is no less than 0.035" to 0.045" for engines built with steel rods. There will be some flex in the crankshaft, rods and pistons as they whip around at speed and this clearance will be diminished as a result\. | ||
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| + | The turbulence caused by the piston coming in close proximity of the underside of the cylinder head will "squish" the unburned mixture out of the area and jet it towards the spark plug, thus fully mixing the mixture. This action contributes to a more complete combustion, more power, less emissions and suppresses detonation. | ||
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| + | [[File:Round dish sbc piston.jpg|thumb|left|340px|This stock type SBC piston is the least desirable design as far as quench action is concerned]][[File:KB P-N 135 SBC 383 PISTON.jpg|thumb|330px|The D-cup design is much better for quench action if a dish is required]] | ||
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| + | The best piston design to use for this is one which has a dead flat area where it will meet the cylinder head. Stock Chevy pistons, for instance, have only a thin band around the perimeter of the piston to accomplish squish. Flat top pistons having minimal valve reliefs will work best. The D-cup pistons offered by various manufacturers also work well (better than a round dish) when a dish is needed. <br style="clear:both"/> | ||
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| + | This is a very important area of engine building and should be considered carefully before ever buying any parts. You must know what the piston deck height (distance from the crown of the piston to the block deck surface with the piston at top dead center) is before continuing. | ||
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| + | A 350 Chevy will be used for this explanation: If the piston deck height is 0.025", then a gasket with a thickness of 0.015" (Fel-Pro FPP-1094) would put the squish at 0.040". If the piston deck height is, 0.012", then a gasket with a thickness of 0.028" (GM 10105117) would put the squish at 0.040". Mix and match the piston deck height with the gasket thickness in your particular application to achieve this ideal 0.035" to 0.045" squish. | ||
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| + | Another consideration is the type of engine- naturally aspirated, supercharged and so on. It's been said that the Cometic MLS (multi-layered steel) gaskets, although relatively expensive, negate the need to "O" ring the block to accommodate higher boost numbers if used with ARP studs. | ||
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| + | ==Head gasket sealants== | ||
| + | Current technology OEM and racing head gaskets are designed to be used without additional sealant, however there are cases where head gasket sealants are required or helpful. Head gaskets sealants are specifically designed for the application; due to extremely high pressure within the combustion chamber which must be contained by the combustion seal, generic sealants such as silicone should not be used for head gasket sealing. Unlike RTV silicone, head gasket sealants do not cure, they remain pliable indefinitely, thereby allowing a proper combustion seal. Conversely, curing sealants such as RTV silicone can form a 'rubber layer' upon which the head/gasket/block interface are separated allowing combustion pressure to eventually form a leak path to the coolant system or to the outside of the engine. This also inhibits heat transfer. Differential expansion rates of bi-metal engines are also accommodated by use of proper head gasket sealants which will not shear because they do not cure. | ||
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| + | ===Standard copper head gaskets and sealant=== | ||
| + | Traditional flat copper head gaskets require the use of additional sealant for cooling and/or oil passage sealing. Similar to steel shim gaskets, traditional copper gaskets have no sealants applied. | ||
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| + | ===Specific head gasket sealant products=== | ||
| + | The following products are commonly used for head gasket sealing: | ||
| + | *[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.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://permatex.com/products/automotive/automotive_gasketing/gasket_sealants.htm various Permatex gasket sealants] | ||
==Replacing blown head gaskets== | ==Replacing blown head gaskets== | ||
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It can also take out the whole bottom end of your engine: hydrolocking, broken or bent pistons and rods, cracked block, etc. | It can also take out the whole bottom end of your engine: hydrolocking, broken or bent pistons and rods, cracked block, etc. | ||
| − | ===Removing | + | ===Removing a head gasket=== |
| − | Use a putty knife or gasket scraper, but be very careful that you do not gouge the material with the tool. Perhaps a better idea is to use a 3M rotary pad that is commercially available for this purpose. Use it in your electric drill to clean off the surfaces perfectly without damage. You can also use acetone thinner, | + | Use a putty knife or gasket scraper, but be very careful that you do not gouge the material with the tool. Perhaps a better idea is to use a 3M rotary pad that is commercially available for this purpose. Use it in your electric drill to clean off the surfaces perfectly without damage. You can also use acetone thinner, or [http://www.permatex.com/products/automotive/automotive_gasketing/gasket_removers/auto_Permatex_Gasket_Remover.htm Permatex gasket remover]. |
Don't use Scotch-Brite pads. | Don't use Scotch-Brite pads. | ||
| − | Don't use wire brushes -- the wires can break off, get into the oil pump, and lock it up | + | Don't use wire brushes -- the wires can break off, get into the oil pump, and lock it up. |
| − | === | + | ===Head gasket repair additives=== |
| − | + | Engine additives that claim to repair questionable head gaskets should only be considered a temporary fix, at best. | |
| − | + | 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") has be used, and it's an ingredient in some commercial head gasket and block/head crack repair additives. It may 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 before it's used and the antifreeze replaced after it has cured. | |
| − | + | 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. | |
| − | + | ==Head gasket torquing== | |
| + | Follow the sequence for the engine being worked on. If no sequence can be found, start from the inner fasteners and work outward. | ||
| − | + | Use at least three steps, i.e. if the torque is 65 ft/lb, torque the first step to 20 ft/lb, second step to 40 ft/lb and the last step to 65 ft/lb. | |
| − | + | [[File:80632permatex.jpg|right]] | |
| − | + | If using OEM fasteners, most times the recommendation is for the clean threads to be lubricated with motor oil before torquing. Threaded holes can be cleaned with a thread chaser. Do not use a tap for this, it can enlarge the hole and/or thin the threads by removing metal, increasing the chance of pulling the threads. | |
| − | + | Fasteners that enter the cooling jackets have to be sealed. Various sealants can be used depending on personal preference. Some sealers are: | |
| − | + | *Hylomar | |
| + | *Permatex #2 | ||
| + | *Permatex High Temp Thread Sealant | ||
| + | *Permatex High Performance Thread Sealant 56521 | ||
| + | *Permatex 80632 with teflon | ||
| + | *[http://www.summitracing.com/parts/ARP-100-9904/ ARP thread sealer] | ||
| + | *Locktite thread sealant | ||
| − | + | Follow the factory torque specs unless aftermarket fasteners are used. In that case, follow the fastener manufacturer's directions for what type of lube to use and what torque to use- this will often differ from the factory specs. | |
| − | + | ||
| − | + | {{Note1}} Do not use RTV or any type of sealant or adhesive that hardens or sets up. The sealant needs to be pliant, not hardened or brittle. | |
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| − | + | ===Head gasket re-torquing=== | |
| − | + | The purpose of re-torquing the cylinder head fasteners is to restore the proper stretch to the head bolts after the first heat cycle. The idea behind this is that the engine assembly will expand as the engine temperature increases, this expansion will increase the compressive load on the head gaskets, causing a seating effect (sometimes referred to as creep relaxation) in composite head gaskets. | |
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| − | + | The seating of the gaskets and threads results in a commensurate relaxation of the fasteners when the engine cools. Re-torquing the fasteners restores the proper stretch to the fasteners which will insure proper cold sealing of the gaskets as well as proper combustion sealing under full load. | |
| − | + | *One re-torque is all that is necessary (unless the manufacturers instructions indicate otherwise) | |
| + | *If your engine uses torque-to-yield head bolts (TTY), do not re-torque | ||
| + | *If there's any doubt, ask the manufacturer for a recommendation | ||
| − | + | ====The process for re-torquing is as follows:==== | |
| + | *Start the engine and run with no load until operating temperature is reached | ||
| + | *Shut down the engine and let cool completely | ||
| + | *Retracing the original torque pattern one fastener at a time, slightly loosen the bolt or nut (to overcome the friction set), then re-torque to the specified torque setting | ||
| − | + | {{!}}It is suggested by some to retorque cast iron heads/blocks while still warm (not hot). Whether or not to do this when using iron castings is up to the builder (''research this beforehand''). But this should NOT be done with aluminum blocks or heads. | |
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===When replacing a blown head gasket=== | ===When replacing a blown head gasket=== | ||
*Check to make sure the heads and block are straight. If they're warped, you could easily end up with another blown head gasket. This can be done with a straight edge and a feeler gauge. This is also a good time to check for cracks. This is especially important if using a thin gasket. The thicker gaskets are made to compensate for low spots on the deck. | *Check to make sure the heads and block are straight. If they're warped, you could easily end up with another blown head gasket. This can be done with a straight edge and a feeler gauge. This is also a good time to check for cracks. This is especially important if using a thin gasket. The thicker gaskets are made to compensate for low spots on the deck. | ||
| − | *Prep the surface. Mating surfaces should be smooth, clean, and dry and can be cleaned with brake cleaner, or denatured alcohol if used in a well-ventilated area | + | *Prep the surface. Mating surfaces should be smooth, clean, and dry and can be cleaned with brake cleaner, or denatured alcohol if used in a well-ventilated area. |
| − | *Chase the bolt and stud holes | + | *Chase the bolt and stud holes with a thread cleaning tool- '''not''' a tap. |
*Pre-fit the head gasket. | *Pre-fit the head gasket. | ||
| − | *Don't use sealant unless the manufacturer explicitly specifies it. | + | *Don't use sealant unless the manufacturer explicitly specifies it. Some engines require NEW torque-to-yield head bolts and these bolts should come with sealant already applied. |
*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. | ||
| − | * | + | *When possible replace both at the same time, even if only one has blown. |
| − | *Oil the tips of the cylinder head bolts with light oil | + | *Oil the tips of the cylinder head bolts with light oil. 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 | + | *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. |
*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. | ||
| − | *Don't be surprised if some of the water ports are "blocked off" on your gasket. Various gaskets are made to differently meter the coolant and direct its flow. Gaskets are also made differently for street and race applications. 400 small block Chevys are a special case. There are steam holes drilled in the block that release steam pockets which are formed in the block as a result of the cylinders being | + | *Don't be surprised if some of the water ports are "blocked off" on your gasket. Various gaskets are made to differently meter the coolant and direct its flow. Gaskets are also made differently for street and race applications. 400 small block Chevys are a special case. There are steam holes drilled in the block that release steam pockets which are formed in the block as a result of the cylinders being siamesed, with no water passage between the cylinders. You must use 400 gaskets on this motor that have the holes in the gasket which coincide with the holes in the block deck. If using heads other than 400 heads (which are also drilled with corresponding holes), you must drill steam holes into the deck of the heads to allow the steam to escape from the block and up into the heads to be dispersed. |
===Re-using head gaskets=== | ===Re-using head gaskets=== | ||
| − | Some head gaskets are | + | Some head gaskets are reusable several times over, while others should never be reused. Most head gaskets are designed for one use only. Composite or graphite head gaskets are most often not reusable because of rust damage to the steel core, disintegration/delamination/peeling of the surface material or damage to or loss of factory-applied sealant material. |
| + | *MLS gaskets are most often not reusable because the elastomeric coating is scrubbed off of the combustion and coolant seals by abrasion from temperature induced expansion and contraction. | ||
| + | *Copper head gaskets are often reusable. Examples are Titan and ICS Titan copper head gaskets from SCE. | ||
| + | *Even if a head gasket may be reusable, many 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. | ||
| + | |||
| + | ==How to differentiate the top and bottom of a head gasket== | ||
| + | Ideally you would install the new gasket the same way as the one your replacing. But if you didn't look closely enough during disassembly then make sure that the coolant, bolt and cylinder holes line up properly. | ||
| + | |||
| + | ==SBC head gasket applications== | ||
| + | Many SBC head gaskets are going to have a 4.090"-4.100" gasket bore diameter, so are usable on a 0.060" over 4" block. | ||
| + | |||
| + | There are a large selection of head gasket types and thicknesses for the SBC engine. Many composite head gaskets are right at 0.041" compressed thickness. Suffice to say ALL manufacturers of SBC head gaskets will have one or more that compress to 0.038"-0.041". | ||
| + | |||
| + | ===SBC head gaskets having less than 0.040" compressed thickness=== | ||
| + | *GM p/n 3830711 is also a steel shim with a 4.1" gasket bore diameter, and is 0.026" thick. Good flat surfaces are required, same rules apply as the Fel-Pro above. This is the GM production gasket for '''non''' 400 bore SBCs. Simple and low cost. | ||
| + | *GM p/n 10105117, this head gasket is a multi-layered stainless steel gasket with a 4.1" gasket bore diameter, is 0.028" thick, works with iron or aluminum heads, good for holding back high compression, and tolerates some surface irregularities in the deck and head surfaces. This is the “revised” gasket, see [http://www.thirdgen.org/techboard/tech-general-engine/269378-head-gasket-thickness-gm.html post #23]. | ||
| + | *GM p/n 14096405, it has stainless faces over a graphite core, 4.1" gasket bore diameter and 0.028" compressed thickness. This thing hangs tough on uneven surfaces and puts up with high compression ratios. Good for iron or aluminum, this makes a good race engine gasket as it's very tolerant of engines running very hot. It lets the block and head move around to adjust for their temperature differences without breaking its seal. | ||
| + | *Victor Reinz Nitroseal p/n 5746, has a compressed thickness is 0.025", 4.1” gasket bore diameter. NAPA carries Victor. | ||
| + | |||
| + | ===Shim type=== | ||
| + | *FelPro's p/n Q1094 is a steel shim with a 4.1" gasket bore diameter and 0.015" compressed thickness. Used in some sportsman drag race and flat top oval track categories. Rubber coated steel shim, 4.100 in. gasket bore diameter, 0.015" compressed thickness. | ||
| + | *SCE #511101 Specialty Component Engineering | ||
| + | **Bore: 4.100" | ||
| + | **Gasket Material: Graphite coated steel core laminate | ||
| + | **Compressed Thickness: 0.015" | ||
| + | **Compressed Volume: 3.245cc | ||
| + | **Lock Wire: No | ||
| + | **Coolant sealing '''not''' compatible with GM lightweight head castings used on 305-350 from 1987-95. | ||
| + | *Mr. Gasket p/n 1130 0.018”- 0.020” compressed thickness, steel embossed w/coating. | ||
| + | *Jegs p/n 210044- embossed shim w/rubber coating. Bore 4.150", compressed thickness is 0.024". | ||
| + | |||
| + | ===400 SBC=== | ||
| + | *[http://www.summitracing.com/parts/CGT-C5248-027/ 400 SBC 0.027” head gasket] | ||
| + | *Felpro p/n's #1004, #1034, #1044 | ||
| + | |||
| + | ===SBC by displacement=== | ||
| + | From [http://www.amotion.com/csb.html amotion.com] | ||
| − | + | *262 Solid steel core 3.850 McCord 7039M | |
| + | *262 Embossed Steel 3.850 McCord 6908 | ||
| + | *267 Solid steel core 3.850 McCord 7039M | ||
| + | *267 Embossed Steel 3.850 McCord 6908 | ||
| + | *283 Graphite 4.090 McCord 7104G | ||
| + | *283 Performance Graphite 4.140 McCord 94-2025 | ||
| + | *283 Solid steel core 4.090 McCord 6631M | ||
| + | *283 Embossed Steel 4.100 McCord 6910 | ||
| + | *302 Graphite 4.090 McCord 7104G | ||
| + | *302 Performance Graphite 4.140 McCord 94-2025 | ||
| + | *302 Solid steel core 4.090 McCord 6631M | ||
| + | *302 Embossed Steel 4.100 McCord 6910 | ||
| + | *305 Solid steel core 3.850 McCord 7039M | ||
| + | *305 Embossed Steel 3.850 McCord 6908 | ||
| + | *307 Graphite 4.090 McCord 7104G | ||
| + | *307 Performance Graphite 4.140 McCord 94-2025 | ||
| + | *307 Solid steel core 4.090 McCord 6631M | ||
| + | *307 Embossed Steel 4.100 McCord 6910 | ||
| + | *327 Graphite 4.090 McCord 7104G | ||
| + | *327 Performance Graphite 4.140 McCord 94-2025 | ||
| + | *327 Solid steel core 4.090 McCord 6631M | ||
| + | *327 Embossed Steel 4.100 McCord 6910 | ||
| + | *350 Graphite 4.090 McCord 7104G | ||
| + | *350 Performance Graphite 4.140 McCord 94-2025 | ||
| + | *350 Solid steel core 4.090 McCord 6631M | ||
| + | *350 Embossed Steel 4.100 McCord 6910 | ||
| + | *400 Graphite 4.180 McCord 6837M | ||
==Suppliers and manufacturers of head gaskets== | ==Suppliers and manufacturers of head gaskets== | ||
| Line 154: | Line 276: | ||
*[http://www.scegaskets.com/ SCE Gaskets] | *[http://www.scegaskets.com/ SCE Gaskets] | ||
*[http://www.victorreinz.com/products.html Victor Reinz gaskets] | *[http://www.victorreinz.com/products.html Victor Reinz gaskets] | ||
| − | |||
| − | |||
==Further reading== | ==Further reading== | ||
| Line 161: | Line 281: | ||
==References== | ==References== | ||
| + | ===Compression calculators=== | ||
| + | ====Static CR==== | ||
| + | *[http://www.wheelspin.net/calc/calc2.html Static compression ratio] | ||
| + | |||
| + | ====Dynamic CR==== | ||
| + | *[http://www.wallaceracing.com/dynamic-cr.php Wallace Racing DCR calculator] | ||
| + | *[http://www.empirenet.com/pkelley2/DynamicCR.html Kelly DCR calculator] | ||
| + | *[http://www.uempistons.com/calc.php?action=comp2 KB/Silvolite DCR calculator] | ||
| + | *[http://www.rbracing-rsr.com/comprAdvHD.htm RSR DCR calculator] | ||
| + | {{Note1}} Some dynamic compression rtatio calculators (like KBs) ask for an additional 15 degrees of duration be added to the IVC @ 0.050" lift point figure. This works OK on older, slower ramped cam lobes, but the faster lobe profiles may need to have 25 degrees or more added to be accurate. | ||
| + | |||
| + | {{Note1}}If the intake valve closing (IVC) point isn't known, it can be calculated: | ||
| + | # Divide the intake duration by 2 | ||
| + | # Add the results to the lobe separation angle (LSA) | ||
| + | # Subtract any ground-in advance | ||
| + | # Subtract 180 | ||
| + | This result does not need to have any amount added to the IVC point, like the KB calculator calls for. | ||
| + | |||
===Forum discussions=== | ===Forum discussions=== | ||
*[http://hotrodders.com/forum/blown-head-gasket-4231.html Blown head gasket?], ''Hotrodders Bulletin Board'', October 28, 2002. | *[http://hotrodders.com/forum/blown-head-gasket-4231.html Blown head gasket?], ''Hotrodders Bulletin Board'', October 28, 2002. | ||
| Line 181: | Line 319: | ||
===Articles=== | ===Articles=== | ||
*[http://www.scegaskets.com/techtips/benefitsof.html Benefits of Copper Head Gaskets] -- SCEGaskets.com | *[http://www.scegaskets.com/techtips/benefitsof.html Benefits of Copper Head Gaskets] -- SCEGaskets.com | ||
| + | *[http://www.enginebuildermag.com/Article/2585/gasket_technology_the_science_of_sealing.aspx Gasket technology] -- Engine Builders Magazine | ||
*[http://www.econofix.com/head.html Cylinder Head and Head Gasket Repairs] -- Econofix.com | *[http://www.econofix.com/head.html Cylinder Head and Head Gasket Repairs] -- Econofix.com | ||
*[http://www.partstrain.com/ShopByDepartment/Head_Gasket Head Gasket] -- Partstrain.com | *[http://www.partstrain.com/ShopByDepartment/Head_Gasket Head Gasket] -- Partstrain.com | ||
| Line 189: | Line 328: | ||
*[http://www.allpar.com/eek/headgasket.html Replacing Chrysler, Dodge, or Plymouth head gaskets] -- Allpar.com | *[http://www.allpar.com/eek/headgasket.html Replacing Chrysler, Dodge, or Plymouth head gaskets] -- Allpar.com | ||
| + | ==Chevy R07 vs. LSx head gaskets== | ||
| + | [[File:LR07 top vs LSx.jpg]] | ||
| + | |||
| + | Chevy racing engine R07 top, LS1 type head gasket bottom. | ||
| + | <br><br> | ||
[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:Good articles]] | [[Category:Good articles]] | ||
| − | + | [[Category:Cylinder head]] | |
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