Head gasket
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====MLS head gaskets==== | ====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. | 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. | ||
| − | 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. | + | 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"/> |
====Graphite head gasket==== | ====Graphite head gasket==== | ||
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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. | 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. | ||
| − | [[File:Round dish sbc piston.jpg|thumb|left|340px|This stock type SBC piston is the least | + | [[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]] |
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"/> | 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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*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== | ==How to differentiate the top and bottom of a head gasket== | ||
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==SBC head gasket applications== | ==SBC head gasket applications== | ||
| − | Many SBC head gaskets are going to have | + | 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. | + | 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=== | ===SBC head gaskets having less than 0.040" compressed thickness=== | ||
| − | *FelPro's | + | *FelPro's p/n 1094 is a steel shim with a 4.1" gasket bore diameter and 0.015" compressed thickness, if you've got super flat surfaces on the deck and head, this is a great gasket. It does not tolerate the engine being overheated. |
| − | *GM 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 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 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 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 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. | + | *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. | |
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| − | Victor Reinz Nitroseal p/n 5746, has a compressed thickness is 0.025", 4.1” gasket bore diameter. NAPA carries Victor. | + | |
===Shim type=== | ===Shim type=== | ||
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There are several thinner coated shim type gaskets like: | There are several thinner coated shim type gaskets like: | ||
| − | *Fel-Pro Q1094- SBC 307 327 350 283 | + | *Fel-Pro p/n Q1094- SBC 307 327 350 283. 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. | ||
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| + | ===400 SBC=== | ||
| + | *[http://www.summitracing.com/parts/CGT-C5248-027/ 400 SBC 0.027” head gasket] | ||
| + | *Felpro p/n's #1004, #1034, #1044 | ||
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| + | ===SBC by displacement=== | ||
| + | From [http://www.amotion.com/csb.html amotion.com] | ||
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| + | *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== | ||
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