Vortec L31 cylinder head

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(→Upgrading and compatibility)
 
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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 1988. But the heads that are being referred to here are from trucks and SUVs produced from 1996-2002.
+
The name "Vortec" can be confusing because GM used that name for their V6 and V8 truck engines as far back as 1985. The origin of the term Vortec was for a combustion chamber design with a ramp port which debuted with the 2.0L motor used with the GM J platform (Cavalier et.al.) which twists the fuel mix similar to a tornado vortice, hence the Vortec nomenclature. 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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==Technical specs==
 
==Technical specs==
−
*Valvespring Seat: 1.300” O.D., 0.850” I.D.
+
*Valve Spring Seat/Base diameters: 1.290” O.D., 0.852” I.D.
−
*Valve-guide Seals: Viton rubber positive seals, total 0.450” retainer-to-seal clearance
+
*Valve Seals: Metal jacketed Viton positive type seals on both intake and exhaust
 +
*Valve Guide Diameter: ID- 11/32" (.343"), Guide OD AKA- Seal Provision: .552"-.555"
 
*Combustion Chamber Volume: 64 cc
 
*Combustion Chamber Volume: 64 cc
 
*Heat Risers: No
 
*Heat Risers: No
−
*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”
+
*Valve springs: Single .177" diameter wire, No Damper, 1.250” O.D., 0.896” I.D., 80-pound seat pressure @ 1.700” installed height, Open test load- 190 Lbs @ 1.270", Coil-bind @ 1.180”, vortec heads will not accept early SBC springs w/ damper. Max lift for stock spring is .460" w/ .060" distance before coil bind.
 +
*Max. Valve Lift: 0.460” which provides 0.030” retainer-to-seal clearance (average overall retainer to seal distance is: .490"-.500")
 
*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 (CFM)
+
!bgcolor="#DDDFFF"|Lift (in.) !!bgcolor="#DDDFFF"|Intake (CFM) !!bgcolor="#DDDFFF"|Exhaust (CFM) !!bgcolor="#DDDFFF"|Exhaust w/ pipe (CFM)
 
|-
 
|-
−
| align="center" |0.100 || align="center" |70 || align="center" |49
+
| align="center" |0.100 || align="center" |70 || align="center" |48 || align="center" |49
 
|-bgcolor="#F1F1F1"
 
|-bgcolor="#F1F1F1"
−
| align="center" |0.200 || align="center" |139 || align="center" |105
+
| align="center" |0.200 || align="center" |139 || align="center" |101 || align="center" |105
 
|-
 
|-
−
| align="center" |0.300 || align="center" |190 || align="center" |137
+
| align="center" |0.300 || align="center" |190 || align="center" |129 || align="center" |137
 
|-bgcolor="#F1F1F1"
 
|-bgcolor="#F1F1F1"
−
| align="center" |0.400 || align="center" |227 || align="center" |151
+
| align="center" |0.400 || align="center" |227 || align="center" |140 || align="center" |151
 
|-
 
|-
−
| align="center" |0.500 || align="center" |239 || align="center" |160
+
| align="center" |0.500 || align="center" |239 || align="center" |147 || align="center" |160
 
|-bgcolor="#F1F1F1"
 
|-bgcolor="#F1F1F1"
−
| align="center" |0.600 || align="center" |229 || align="center" |162
+
| align="center" |0.600 || align="center" |229 || align="center" |151 || 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 0.420"
+
* Springs if the cam has a valve lift over about 0.440"
 
* 1987 to present center bolt style valve covers if the heads used previously were perimeter style (1986 and earlier including the current production Goodwrench 350 crate motor)
 
* 1987 to present center bolt style valve covers if the heads used previously were perimeter style (1986 and earlier including the current production Goodwrench 350 crate motor)
 
** 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 (SBC and 4.3L since the 1988 model year use the self aligning rockers and the pushrod holes are round instead of oblong - self aligning rockers do retrofit to the earlier heads but recommended for a stock rebuild
−
* Valve cover gaskets
+
* Valve cover gaskets (again 87+ centerbolt style)
−
* 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; some applications require the stock SBC intake to have the upper section rewelded with a chunk of metal which covers the intake ports as demonstrated with the SyTy 4.3L or TPI intake base (it is common for the SyTy 4.3L lower intake to be modified with extra material when used with Vortec heads)
 
* Vortec specific intake manifold gasket
 
* Vortec specific intake manifold gasket
 
* Vortec specific intake manifold bolts
 
* Vortec specific intake manifold bolts
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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 (.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 Vortec valve springs are single wound without a damper and are 1.250" diameter. The damping is done by the spring ID (.896") being a close fit to the guide boss OD (0.852"); 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 0.420" 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:  
+
The stock springs are not suited for high performance use or for lifts above about 0.460" 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 0.845" 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.
+
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 0.852" 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 guide 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 0.560-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>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 0.555-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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====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>&nbsp;'''CFM'''&nbsp;</td><td>'''Lift''' (in.)</td><td>&nbsp;'''CFM'''&nbsp;</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>&nbsp;'''CFM'''&nbsp;</td><td>'''Lift''' (in.)</td><td>&nbsp;'''CFM'''&nbsp;</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 - intake does not have the power brake booster vacuum port located on the LH side, needed when used with a 1987-'95 TBI equipped Chevrolet/GMC 305 or 350 - some GMT400 light duty trucks and G-series vans including the forward control chasssis will have a hydroboost brake booster in lieu of a vacuum assist power brake booster]]  
 
|[[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
 +
* Bosch 4505
 +
* Bosch 4458
  
 
==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
 +
 +
The L31 (and L30) small block, along with the 4.3L (L35, LU3) came with a redesigned water pump with a threaded boss on the impeller which accepts a fan clutch held with a nut instead of the 4 bolt setup common with 1995 and earlier SBCs. A water pump bypass port was added to the intake manifold where the cylinder block for 1996+ will have the water pump bypass hole eliminated - some 1996-2003 production cylinder blocks will have the bypass hole eliminated and undrilled (visual cue is the RH water pump port where the bypass hole is absent and undrilled - this also includes cylinder blocks with 2 holes undrilled for the timing cover (much like engine blocks casted after 1992 the fuel pump hole is undrilled and unmachined - aftermarket 5.7L crate motor assemblies including the L31 used by Mercury Marine/MerCruiser will have the water pump bypass hole and fuel pump hole drilled out and machined. One solution is the following - use a high flow thermostat or run a water bypass from the heater hose port to the radiator and/or heater core.
  
 
==Optional GMPP Vortec parts==
 
==Optional GMPP Vortec parts==
Line 736: Line 723:
  
 
<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>
 +
 +
</tr>
 +
<tr class="wbg-blacktext" align="center" valign="top">
 +
 +
<td class="wbg-blacktext" align="center" valign="top">Vsk4h53</td>
 +
 +
<td class="wbg-blacktext" align="center" valign="top">Alex's Parts valve spring kit. Drop in fit, machine work not required up to .550" Lift, Hyd Roller.</td>
 +
</tr>
 +
<tr class="wbg-blacktext" align="center" valign="top">
 +
 +
<td class="wbg-blacktext" align="center" valign="top">Vsk4h50</td>
 +
 +
<td class="wbg-blacktext" align="center" valign="top">Alex's Parts valve spring kit. Drop in fit, machine work not required up to .550" Lift, Hyd Flat Tappet.</td>
  
 
</tr>
 
</tr>

Latest revision as of 22:22, 10 July 2020

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