Editing Vortec L31 cylinder head
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The Chevrolet L31 5.7L Vortec cylinder head is the best flowing production head Chevy has made for the Gen I SBC engine to date. Because of this, it has become a very popular swap. | The Chevrolet L31 5.7L Vortec cylinder head is the best flowing production head Chevy has made for the Gen I SBC engine to date. Because of this, it has become a very popular swap. | ||
− | The name "Vortec" can be confusing because GM used that name for their V6 and V8 truck engines as far back as | + | The name "Vortec" can be confusing because GM used that name for their V6 and V8 truck engines as far back as 1988. But the heads that are being referred to here are from trucks and SUVs produced from 1996-2002. |
They are made of cast iron, have 170cc nominal intake runners, and 64cc nominal combustion chamber volume (actual volumes may vary due to production tolerances and/or modifications done previously, so volumes, especially the combustion chamber volume, has to be determined by measuring, or "CC'ing" the chamber). | They are made of cast iron, have 170cc nominal intake runners, and 64cc nominal combustion chamber volume (actual volumes may vary due to production tolerances and/or modifications done previously, so volumes, especially the combustion chamber volume, has to be determined by measuring, or "CC'ing" the chamber). | ||
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*engines that do '''not''' have the thermostat removed. A missing thermostat is an indication the engine was running hot. | *engines that do '''not''' have the thermostat removed. A missing thermostat is an indication the engine was running hot. | ||
*engines that still have antifreeze in them. Engines with straight water, or without any coolant showing, may well have been losing coolant. No one replaces leaking coolant with antifreeze- they will use straight water "until I fix it". By then, it's often too late. | *engines that still have antifreeze in them. Engines with straight water, or without any coolant showing, may well have been losing coolant. No one replaces leaking coolant with antifreeze- they will use straight water "until I fix it". By then, it's often too late. | ||
− | *engines with water in the oil or oil in the water. This is a sure sign of a blown head | + | *engines with water in the oil or oil in the water. This is a sure sign of a blown head gasket or cracked casting, either of which can lead to overheating and cracked heads. |
+ | *vehicles that do not have antifreeze receipts or antifreeze or water jugs laying around inside the vehicle. That's another sure sign there was a problem with the cooling system. | ||
*Look for heads having a spark plug (or spark plugs from adjacent cylinders) with no unusually colored deposits- or a lack of deposits that were removed by coolant getting into the chamber(s). Head gaskets leaking or a cracked casting that lets coolant into the combustion chamber will make the plugs look a lot different than a normal plug- look for uniformity. | *Look for heads having a spark plug (or spark plugs from adjacent cylinders) with no unusually colored deposits- or a lack of deposits that were removed by coolant getting into the chamber(s). Head gaskets leaking or a cracked casting that lets coolant into the combustion chamber will make the plugs look a lot different than a normal plug- look for uniformity. | ||
*Look for engines that do not have evidence of stop leak in the radiator/cooling system. If it has stop leak, it was leaking. If it was leaking there's too big of a chance it overheated and cracked the heads. | *Look for engines that do not have evidence of stop leak in the radiator/cooling system. If it has stop leak, it was leaking. If it was leaking there's too big of a chance it overheated and cracked the heads. | ||
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==Technical specs== | ==Technical specs== | ||
− | * | + | *Valvespring Seat: 1.300” O.D., 0.850” I.D. |
− | *Valve Seals: | + | *Valve-guide Seals: Viton rubber positive seals, total 0.450” retainer-to-seal clearance |
− | + | ||
*Combustion Chamber Volume: 64 cc | *Combustion Chamber Volume: 64 cc | ||
*Heat Risers: No | *Heat Risers: No | ||
− | *Valve springs: Single | + | *Valve springs: Single wire with damper 1.235” O.D., 0.875” I.D. 75-pound seat pressure @ 1.700” installed height Coil-bind @ 1.150” |
− | + | ||
*Rocker Arm Type: Self-Aligning | *Rocker Arm Type: Self-Aligning | ||
*Intake Runner Volume: 170 cc | *Intake Runner Volume: 170 cc | ||
*Valve Diameter: I: 1.94”, E: 1.50” | *Valve Diameter: I: 1.94”, E: 1.50” | ||
*Casting Numbers: 10239906 and 12558062 | *Casting Numbers: 10239906 and 12558062 | ||
+ | *Max. Valve Lift: 0.420” which allows 0.030” retainer-to-seal | ||
*Rocker Stud: Press-in, 3/8” diameter | *Rocker Stud: Press-in, 3/8” diameter | ||
*Spark plug: 14 mm, 3/4" reach, tapered seat | *Spark plug: 14 mm, 3/4" reach, tapered seat | ||
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==Flow rate of L31 Vortec heads== | ==Flow rate of L31 Vortec heads== | ||
{| style="color:black; cellpadding="2" cellspacing="0" border="1" | {| style="color:black; cellpadding="2" cellspacing="0" border="1" | ||
− | !bgcolor="#DDDFFF"|Lift (in.) !!bgcolor="#DDDFFF"|Intake (CFM) !!bgcolor="#DDDFFF"|Exhaust | + | !bgcolor="#DDDFFF"|Lift (in.) !!bgcolor="#DDDFFF"|Intake (CFM) !!bgcolor="#DDDFFF"|Exhaust (CFM) |
|- | |- | ||
− | | align="center" |0.100 || align="center" |70 | + | | align="center" |0.100 || align="center" |70 || align="center" |49 |
|-bgcolor="#F1F1F1" | |-bgcolor="#F1F1F1" | ||
− | | align="center" |0.200 || align="center" |139 | + | | align="center" |0.200 || align="center" |139 || align="center" |105 |
|- | |- | ||
− | | align="center" |0.300 || align="center" |190 | + | | align="center" |0.300 || align="center" |190 || align="center" |137 |
|-bgcolor="#F1F1F1" | |-bgcolor="#F1F1F1" | ||
− | | align="center" |0.400 || align="center" |227 | + | | align="center" |0.400 || align="center" |227 || align="center" |151 |
|- | |- | ||
− | | align="center" |0.500 || align="center" |239 | + | | align="center" |0.500 || align="center" |239 || align="center" |160 |
|-bgcolor="#F1F1F1" | |-bgcolor="#F1F1F1" | ||
− | | align="center" |0.600 || align="center" |229 | + | | align="center" |0.600 || align="center" |229 || align="center" |162 |
|- | |- | ||
|} | |} | ||
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<tr class="wbg-blacktext" align="left" valign="top"> | <tr class="wbg-blacktext" align="left" valign="top"> | ||
<td class="wbg-blacktext" colspan="7" align="left" valign="top"><span class="wbg-blacktext-12pxB">'''Note''':</span> Vortec L31 and Stock Iron 882 flow data where obtained from Car Craft Magazine’s Web site in their Technical Articles section. The Fast Burn (new version) flow data is Chevrolet’s data.</td></tr></table><br> | <td class="wbg-blacktext" colspan="7" align="left" valign="top"><span class="wbg-blacktext-12pxB">'''Note''':</span> Vortec L31 and Stock Iron 882 flow data where obtained from Car Craft Magazine’s Web site in their Technical Articles section. The Fast Burn (new version) flow data is Chevrolet’s data.</td></tr></table><br> | ||
+ | {{!}} It's unknown at this time why there's a discrepancy in the exhaust flow of the Vortec heads between the two tables. | ||
==Upgrading and compatibility== | ==Upgrading and compatibility== | ||
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There are some inherent costs associated in swapping from 1995-back heads to the L31 Vortec heads. Here is a list of items to be purchased and/or labor associated with the upgrade: | There are some inherent costs associated in swapping from 1995-back heads to the L31 Vortec heads. Here is a list of items to be purchased and/or labor associated with the upgrade: | ||
* L31 heads | * L31 heads | ||
− | * Springs if the cam has a valve lift over about 0. | + | * Springs if the cam has a valve lift over about 0.420" |
− | * | + | * Center bolt style valve covers if the heads used previously were perimeter style |
** Note: [http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head#Small_port_Vortec_head_p.2Fn_25534351_.28bare.29_and_p.2Fn_25534421_.28assembled.29 GMPP small and large port Vortec heads] and other aftermarket Vortec heads accept either perimeter or center bolt valve covers [[File:Vortec valve-rocker.jpg|thumb|right|300px|Self aligning stamped steel rockers]] | ** Note: [http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head#Small_port_Vortec_head_p.2Fn_25534351_.28bare.29_and_p.2Fn_25534421_.28assembled.29 GMPP small and large port Vortec heads] and other aftermarket Vortec heads accept either perimeter or center bolt valve covers [[File:Vortec valve-rocker.jpg|thumb|right|300px|Self aligning stamped steel rockers]] | ||
− | *Self aligning rocker arms | + | *Self aligning rocker arms |
− | * Valve cover gaskets | + | * Valve cover gaskets |
− | * Vortec specific intake manifold. While some aftermarket heads have both 12 and 8 bolt intake bolt patterns, the height of the Vortec ports require a tall, "raised port" type early intake manifold (along with porting/port work to the intake manifold and/or head), to even come close to fitting correctly. See '''[[Vortec_L31_cylinder_head#Using an early style intake on an aftermarket Vortec-type head|Using an early style intake on an aftermarket Vortec-type head]]''' for more info | + | * Vortec specific intake manifold. While some aftermarket heads have both 12 and 8 bolt intake bolt patterns, the height of the Vortec ports require a tall, "raised port" type early intake manifold (along with porting/port work to the intake manifold and/or head), to even come close to fitting correctly. See '''[[Vortec_L31_cylinder_head#Using an early style intake on an aftermarket Vortec-type head|Using an early style intake on an aftermarket Vortec-type head]]''' for more info |
* Vortec specific intake manifold gasket | * Vortec specific intake manifold gasket | ||
* Vortec specific intake manifold bolts | * Vortec specific intake manifold bolts | ||
− | * Head bolts (required only if the original head bolts are either missing or unusable for some reason | + | * Head bolts (required only if the original head bolts are either missing or unusable for some reason) |
* Head gaskets ([http://www.crankshaftcoalition.com/wiki/Head_gasket#Re-using_head_gaskets generally required] any time heads are re-installed) | * Head gaskets ([http://www.crankshaftcoalition.com/wiki/Head_gasket#Re-using_head_gaskets generally required] any time heads are re-installed) | ||
* Machining valve guide boss or the use of different retainers and springs, or ghetto grinding the stock retainers, etc., to work with a camshaft having somewhere around 0.450" or more valve lift. | * Machining valve guide boss or the use of different retainers and springs, or ghetto grinding the stock retainers, etc., to work with a camshaft having somewhere around 0.450" or more valve lift. | ||
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[[File:Vortec beehive.jpg|thumb|left|300px|Straight wound spring, Left; Beehive spring, right]] | [[File:Vortec beehive.jpg|thumb|left|300px|Straight wound spring, Left; Beehive spring, right]] | ||
<br style="clear:both"/> | <br style="clear:both"/> | ||
− | The stock Vortec valve springs are single wound without a damper and are 1.250" diameter. The damping is done by the spring ID (. | + | The stock Vortec valve springs are single wound without a damper and are 1.250" diameter. The damping is done by the spring ID (.880") being a close fit to the guide boss OD (0.845"); this damps the spring without the added cost of an inner flat wound damper seen on the Gen 1 SBC throughout its production. If you have aftermarket springs designed for the earlier heads, you must remove the inner damper because the damper ID will be too small to fit over the guide boss without it being cut smaller. If the boss is cut smaller, a damper should be used. |
− | The stock springs are not suited for high performance use or for lifts above about 0. | + | The stock springs are not suited for high performance use or for lifts above about 0.420" using stock retainers. There are several replacements for the stock springs, among the best is the beehive spring and retainer combination from Comp Cams, originally designed for the LS engine series: |
*'''[http://www.compcams.com/WhatsNew/NewsDetails.aspx?ListHistoryID=164462240 p/n 26915]'''- 105 pounds at 1.8" installed height; open pressure 293 lbs. at 1.2"; coil bind at 1.100"; spring rate 313 lbs./in.; bottom OD 1.290" | *'''[http://www.compcams.com/WhatsNew/NewsDetails.aspx?ListHistoryID=164462240 p/n 26915]'''- 105 pounds at 1.8" installed height; open pressure 293 lbs. at 1.2"; coil bind at 1.100"; spring rate 313 lbs./in.; bottom OD 1.290" | ||
*'''[http://www.compcams.com/WhatsNew/NewsDetails.aspx?ListHistoryID=1166393320 p/n 26918]'''- 125 pounds at 1.8" installed height; open pressure 367 pounds at 1.15"; coil bind 1.100"; spring rate 372 lbs./in.; '''bottom OD 1.310"''' <br> | *'''[http://www.compcams.com/WhatsNew/NewsDetails.aspx?ListHistoryID=1166393320 p/n 26918]'''- 125 pounds at 1.8" installed height; open pressure 367 pounds at 1.15"; coil bind 1.100"; spring rate 372 lbs./in.; '''bottom OD 1.310"''' <br> | ||
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==Valve guide boss== | ==Valve guide boss== | ||
[[File:900 guide boss1.jpg|thumb|450px|left|Stock Vortec boss is 0.845"OD]] | [[File:900 guide boss1.jpg|thumb|450px|left|Stock Vortec boss is 0.845"OD]] | ||
− | For performance use, often the guide boss will be shortened to allow more lift without retainer to seal clearance problems. Along with that, the guide boss OD can be machined down from 0. | + | For performance use, often the guide boss will be shortened to allow more lift without retainer to seal clearance problems. Along with that, the guide boss OD can be machined down from 0.845" to a smaller common diameter, like 0.785" of the original Gen1 SBC heads, so aftermarket springs (double or with dampers) can be used. At the same time the top of the boss where the seal is located can be machined from 0.555" (stock) to a smaller diameter like 0.530" to use commonly available seals. |
<br style="clear:both"/> | <br style="clear:both"/> | ||
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;From an article by editor Jeff Smith: | ;From an article by editor Jeff Smith: | ||
− | <blockquote>The Comp Cams cutter increases the spring-seat diameter while simultaneously reducing the outside diameter (OD) of the guide boss. The Crane tool also cuts the valve-guide-seal diameter at the same time. Comp sells a separate tool that cuts a new guide seal and reduces the guide height to create additional retainer-to-seal clearance. Both cutters machine the top of the guide down to a 0.530-inch diameter, which is the standard size for positive-type aftermarket seals. This requires purchasing new valve-guide seals, since the factory uses a 0. | + | <blockquote>The Comp Cams cutter increases the spring-seat diameter while simultaneously reducing the outside diameter (OD) of the guide boss. The Crane tool also cuts the valve-guide-seal diameter at the same time. Comp sells a separate tool that cuts a new guide seal and reduces the guide height to create additional retainer-to-seal clearance. Both cutters machine the top of the guide down to a 0.530-inch diameter, which is the standard size for positive-type aftermarket seals. This requires purchasing new valve-guide seals, since the factory uses a 0.560-inch guide to locate the seals. Another way to go is to have a machine shop cut the guide boss diameter to around 0.760 inch and reduce the seal height and use either the Crane H-11 tool steel spring (PN 99846) or the Comp spring (PN 981). |
</blockquote> | </blockquote> | ||
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==Pushrod guide holes== | ==Pushrod guide holes== | ||
− | [[File:Vortec head p-rod hole enlargement.jpg|thumb|Vortec head enlarging pushrod hole]]Vortec heads have a 7/16" round pushrod hole in the head; earlier non self aligning rocker arm equipped heads have a 7/16" x 11/32" | + | [[File:Vortec head p-rod hole enlargement.jpg|thumb|Vortec head enlarging pushrod hole]]Vortec heads have a 7/16" round pushrod hole in the head; earlier non self aligning rocker arm equipped heads have a 7/16" x 11/32" ovoid hole in them. |
===So what this means is three things:=== | ===So what this means is three things:=== | ||
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====Large port Vortec flow chart==== | ====Large port Vortec flow chart==== | ||
<table border="5" cellspacing="0" cellpadding="5"><tr valign="top" tr bgcolor="#CCCCFF"><td colspan="2"><center>'''INTAKE'''</center></td><td colspan="2"><center>'''EXHAUST'''</center></td></tr><tr valign="top" tr bgcolor="#FFF8DC"><td>'''Lift''' (in.)</td><td> '''CFM''' </td><td>'''Lift''' (in.)</td><td> '''CFM''' </td></tr><tr valign="top"><td>0.200</td><td>128.6</td><td>0.200</td><td>100.8</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.300</td><td>188.4</td><td>0.300</td><td>138.6</td></tr><tr valign="top"><td>0.400</td><td>234.8</td><td>0.400</td><td>154.4</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.500</td><td>257.2</td><td>0.500</td><td>152.5</td></tr><tr valign="top"><td>0.600</td><td>263.2</td><td>0.600</td><td>163.8</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.700</td><td>269.1</td><td>0.700</td><td>167.0</td></tr></table> | <table border="5" cellspacing="0" cellpadding="5"><tr valign="top" tr bgcolor="#CCCCFF"><td colspan="2"><center>'''INTAKE'''</center></td><td colspan="2"><center>'''EXHAUST'''</center></td></tr><tr valign="top" tr bgcolor="#FFF8DC"><td>'''Lift''' (in.)</td><td> '''CFM''' </td><td>'''Lift''' (in.)</td><td> '''CFM''' </td></tr><tr valign="top"><td>0.200</td><td>128.6</td><td>0.200</td><td>100.8</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.300</td><td>188.4</td><td>0.300</td><td>138.6</td></tr><tr valign="top"><td>0.400</td><td>234.8</td><td>0.400</td><td>154.4</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.500</td><td>257.2</td><td>0.500</td><td>152.5</td></tr><tr valign="top"><td>0.600</td><td>263.2</td><td>0.600</td><td>163.8</td></tr><tr bgcolor="#F1F1F1" valign="top"><td>0.700</td><td>269.1</td><td>0.700</td><td>167.0</td></tr></table> | ||
+ | |||
+ | ==Vortec intake manifolds== | ||
+ | The L30 5.0L and L31 5.7L Vortec engines never came with a carb; they all used EFI so did not need a heat crossover port in the heads. GMPP and the aftermarket sell various carburetor and TBI intakes to fit the Vortec heads, so using a carb or TBI with Vortec heads is easy. Some GMPP Vortec intakes have the provision to run coolant through the plenum area to provide intake heat. | ||
+ | |||
+ | ===Using an early style intake on an aftermarket Vortec-type head=== | ||
+ | Vortec heads use an intake manifold having 8 instead of 12 bolts. Also, Vortec intake ports are taller than earlier SBC heads; there's not enough metal above the port (except on "raised port" aftermarket intakes) to allow the head and intake port to match up. That means earlier 12 bolt intakes will not match up to the Vortec bolt pattern or ports. | ||
+ | |||
+ | Many aftermarket Vortec style heads (including Bow Tie Vortec heads) feature dual bolt patterns allowing the use of the early 12-bolt intakes. This has a very limited use. | ||
+ | |||
+ | Commonly available 12 bolt SBC dual plane intakes do not have enough metal above the port to be ported to match the Vortec port, w/o having a vacuum leak or razor thin sealing surfaces above the ports. An early intake would need at least 0.325" of material above the intake port opening to have any chance of sealing, and that doesn't take the difference in the port width/location into account. Because of the height of the Vortec intake port, only the single plane 'raised port' race intakes have enough height to actually match up to the Vortec head intake port- but even then the ports may be too wide or have other fitment issues. | ||
+ | |||
+ | Because of these differences, a Vortec-specific intake should be used. | ||
+ | ;Chevrolet says<nowiki>:</nowiki> | ||
+ | <blockquote> | ||
+ | Do not try to modify either the heads or the intake manifold to try to make the Vortec heads match up to a standard 12-bolt intake manifold. The ports will not match up. You must use a Vortec style intake manifold with any Vortec style cylinder head. | ||
+ | </blockquote> | ||
+ | ;Return to '''[[Vortec_L31_cylinder_head#Upgrading and compatibility|''Upgrading and compatibility'']]''' | ||
==Intake gaskets== | ==Intake gaskets== | ||
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|} | |} | ||
{| | {| | ||
− | |[[File:Gmpp vortec tbi intake.jpg|thumb|center|420px|TBI intake p/n 12496821 from GMPP | + | |[[File:Gmpp vortec tbi intake.jpg|thumb|center|420px|TBI intake p/n 12496821 from GMPP]] |
|[[File:12366573 - GMPP Vortec dual plane intake manifold.jpg|thumb|center|270px|Dual plane GMPP intake p/n 12366573]] | |[[File:12366573 - GMPP Vortec dual plane intake manifold.jpg|thumb|center|270px|Dual plane GMPP intake p/n 12366573]] | ||
|[[File:Gmpp 12496822 open plenum.jpg|thumb|center|420px|GMPP p/n 12496822 open plenum intake]] | |[[File:Gmpp 12496822 open plenum.jpg|thumb|center|420px|GMPP p/n 12496822 open plenum intake]] | ||
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* Bosch HR10BX | * Bosch HR10BX | ||
* Bosch HR9DC | * Bosch HR9DC | ||
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==Vortec water bypass== | ==Vortec water bypass== | ||
8[http://www.hotrodders.com/forum/thermostat-bypass-vortec-conversion-161468.html#post1581704 Thermostat bypass] Hotrodders forum thread | 8[http://www.hotrodders.com/forum/thermostat-bypass-vortec-conversion-161468.html#post1581704 Thermostat bypass] Hotrodders forum thread | ||
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− | |||
==Optional GMPP Vortec parts== | ==Optional GMPP Vortec parts== | ||
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<td class="wbg-blacktext" align="center" valign="top">Crane Cams valve spring and retainer kit. Drop-in springs with no machine work needed.</td> | <td class="wbg-blacktext" align="center" valign="top">Crane Cams valve spring and retainer kit. Drop-in springs with no machine work needed.</td> | ||
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</tr> | </tr> | ||
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* [[Valve train points to check]] | * [[Valve train points to check]] | ||
* [[Quench]] | * [[Quench]] | ||
− | * [http://www.compcams.com/information/Articles/Type/Chevrolet/CC_CHP0201-002.asp Vortec head chronicles.] | + | * [[http://www.compcams.com/information/Articles/Type/Chevrolet/CC_CHP0201-002.asp Vortec head chronicles.]] |
<br><br> | <br><br> | ||