Vortec L31 cylinder head
From Crankshaft Coalition Wiki
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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 0.440" |
* 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]] | ||
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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]] | ||
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| − | 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 (.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. | + | 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. | + | 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. |
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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 0.555-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). |
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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 class="wbg-blacktext" align="center" valign="top"> | ||
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| + | <td class="wbg-blacktext" align="center" valign="top">Vsk4h53</td> | ||
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| + | <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"> | ||
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| + | <td class="wbg-blacktext" align="center" valign="top">Vsk4h50</td> | ||
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| + | <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> | ||
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