Editing Vortec L31 cylinder head (section)
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==Valve springs, retainers and locks== [[File:Vortec beehive.jpg|thumb|left|300px|Straight wound spring, Left; Beehive spring, right]] <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 (.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 0.460" 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=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> {{Note1}}The p/n 26918 springs requires the spring pocket be opened up using Comp Cams tool p/n 4721 or equivalent so there's no binding. The p/n 26918 springs were updated, check w/Comp Cams to be sure these specs are current. *'''[http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=26981-16&Category_Code= p/n 26981]'''- 110 pounds at 1.70" installed height; open pressure 292 lbs. at 1.175"; coil bind 1.115"; spring rate 347 lb./in.; bottom OD 1.240" The beehive springs above need to be installed using the correct retainer for a Vortec valve, like Comp Cams p/n 787 (steel) or p/n 788 (titanium), NOT a retainer originally for the LSx engines; the LSx engines have 8mm metric valve stems. Also note the specs are with an installed height of 1.8". The image below shows the difference in installed height when using different retainers: [[File:787-LEFT; 774-RIGHT (Gen III).gif|frame|left|300px|Retainer p/n 787 left; p/n 774 right]] <br style="clear:both"/> On the other end of the cost scale is the use of inexpensive "Z-28/LT-1" springs (or any spring with a ~1.70" installed height and a 1.25" OD) with the damper removed along with the stock retainers that have had some of the bottom ground off to provide more clearance (sometimes referred to as the "ghetto grind"). This will allow more lift (in the area of 0.500") without changing the guide boss height or diameter. Chevrolet recommends using the [http://www.summitracing.com/parts/crn-10309-1 Crane Cam p/n 10309-1] drop-in valve spring/retainer kit which is good for 0.550” lift (this allows about 0.025" between the retainer and seal) with no machining. The spring rate for this spring is 409 lb/in and has a 0.870" ID. When retaining the factory boss and seals, be sure the valve seals are driven on all the way. You need to check that they are before installing this kit. Use a 3/8” drive 1/2” socket and a soft mallet to gently drive the seals fully home. ;Also see<nowiki>:</nowiki> *[http://www.thirdgen.org/techboard/tech-general-engine/542295-ls6-valvetrain-vortec-heads.html LS6 Valvetrain on vortec heads] *[http://www.thirdgen.org/techboard/tech-general-engine/562935-rework-vortec-heads.html Vortec valvetrain mods] ===Other springs=== The following valve springs are single w/either no damper or damper removed. They fit the stock seat, guide boss, seal, and retainer unless otherwise noted. *Comp p/n 981 *Crane p/n 99846: H-11 tool steel *Crane p/n 144845: Performance hydraulic roller cams, PAC enhanced wire, no damper **OD: 1.265" **ID: 0.865" **Seat pressure: 120 lbs @ 1.750" **Open pressure: 358 lbs @ 1.250" **Coil bind: 1.100" **Rate: 476 lbs/in. **Max net lift: 0.600" *Isky p/n 205D *Lunati p/n 73943 *Manley p/n 22410, fit without machining, allow 0.520" lift **Seat pressure: 125 lbs **Open pressure: 340 lbs @ 0.500" lift **Retainer p/n 23652 {{Note1}} K Motion K-700 springs have been reported by one member of Hotrodders.com to be breakage prone. Another member (this writer) has had several sets of 1.25" OD single springs with damper (p/n unknown) break the dampers on a 0.480" net lift hydraulic cam SBC application. Whether these problems were transient or ongoing is unknown. If these springs are being considered, research them first. ===Locks=== {{Note1}}On Vortec and other heads using self aligning rocker arms, using a +0.050" lock can cause interference between the rocker tip and the locks/retainer. Rocker contacting the locks/retainer has been encountered using a combination of c/n 906 Vortec heads, Comp Pro Magnum rockers p/n 1317, Comp retainer p/n 787, Comp spring p/n 26918, and the +0.050" locks. The engine builder must mock up the assembly and check the clearance closely. In the case there's insufficient clearance, there are a few options: *Use non self aligning rocker arms. Requires guide plates be installed. *Use longer valves *Use a different spring/retainer combo that uses a standard lock *If just the locks are hitting the rocker, using a shorter (lash cap compatible) lock like the Edelbrock p/n 9615 may help. This 7 degree lock is 0.050" lower than a regular lock. *{{!}}Use extreme caution if making the spring seat any deeper. A tool to help determine the installed height using different retainers and/or locks is the Howards Cams p/n 92010, shown immediately below: [[File:Ret height92010.jpg]] ===Spring seat=== Use caution if making the seat larger, there have been a few warnings about cracks developing on heads with enlarged seats. Maximum spring seat diameter is 1.44". Use reduced hex head bolts or 12 point fasteners to give more clearance if a larger seat like for a 1.44" OD spring is used. Do not make the spring seat deeper. If more installed height is required, get it from a different retainer, locks, or a longer valve stem.
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