Vortec L31 cylinder head
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| − | <td class="ltbluebg-blacktextbold-12px" colspan="3" align="center" valign="top">'''Intake Flow Comparison'''</td> | + | <td bgcolor="#CCCCFF" class="ltbluebg-blacktextbold-12px" colspan="3" align="center" valign="top">'''Intake Flow Comparison'''</td> |
| − | <td class="ltyellowbg-blacktext-12pxB" colspan="3" align="center" valign="top">'''Exhaust Flow Comparison'''</td></tr> | + | <td bgcolor="#CCCCFF" class="ltyellowbg-blacktext-12pxB" colspan="3" align="center" valign="top">'''Exhaust Flow Comparison'''</td></tr> |
<tr align="left" bgcolor="#CCCCFF" valign="top"> | <tr align="left" bgcolor="#CCCCFF" valign="top"> | ||
<td bgcolor="#FFF8DC" class="ltorangebg-blacktext-14pxB" align="center" valign="top" width="92">'''Valve Lift'''</td> | <td bgcolor="#FFF8DC" class="ltorangebg-blacktext-14pxB" align="center" valign="top" width="92">'''Valve Lift'''</td> | ||
| − | <td bgcolor="# | + | <td bgcolor="#FFF8DC" class="oceanbluebg-blacktext" align="center" valign="top" width="92">'''GMPP'''<br> |
'''Fast Burn'''</td> | '''Fast Burn'''</td> | ||
| − | <td class="ltpinkPowderbg-bk12" align="center" valign="top" width="92">'''GM'''<br> | + | <td bgcolor="#FFF8DC" class="ltpinkPowderbg-bk12" align="center" valign="top" width="92">'''GM'''<br> |
'''Vortec L31'''</td> | '''Vortec L31'''</td> | ||
<td bgcolor="#FFF8DC" class="msdbg-blacktext" align="center" valign="top" width="92">'''GM<br>Stock''' '''Iron 882'''</td> | <td bgcolor="#FFF8DC" class="msdbg-blacktext" align="center" valign="top" width="92">'''GM<br>Stock''' '''Iron 882'''</td> | ||
| − | <td bgcolor="# | + | <td bgcolor="#FFF8DC" class="oceanbluebg-blacktext" align="center" valign="top" width="92">'''GMPP'''<br> |
'''Fast Burn'''</td> | '''Fast Burn'''</td> | ||
| − | <td class="ltpinkPowderbg-bk12" align="center" valign="top" width="92">'''GM'''<br> | + | <td bgcolor="#FFF8DC" class="ltpinkPowderbg-bk12" align="center" valign="top" width="92">'''GM'''<br> |
'''Vortec L31'''</td> | '''Vortec L31'''</td> | ||
<td bgcolor="#FFF8DC" class="msdbg-blacktext" align="center" valign="top" width="92">'''GM <br>Stock''' | <td bgcolor="#FFF8DC" class="msdbg-blacktext" align="center" valign="top" width="92">'''GM <br>Stock''' | ||
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*Manley p/n 22410, fit without machining, allow 0.520" lift | *Manley p/n 22410, fit without machining, allow 0.520" lift | ||
**Seat pressure: 125 lbs | **Seat pressure: 125 lbs | ||
| − | *Open pressure: 340 lbs @ 0.500" lift | + | **Open pressure: 340 lbs @ 0.500" lift |
** Retainer p/n 23652 | ** Retainer p/n 23652 | ||
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{{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 break the dampers on a 0.480" net lift hydraulic cam SBC application. Whether these problems were transient or ongoing remains to be seen. If these springs are being considered, research them first. | {{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 break the dampers on a 0.480" net lift hydraulic cam SBC application. Whether these problems were transient or ongoing remains to be seen. If these springs are being considered, research them first. | ||
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<br style="clear:both"/> | <br style="clear:both"/> | ||
| − | ===Tooling=== | + | ====Tooling==== |
[[File:Tool.jpg|thumb|450px|Comp tooling]] | [[File:Tool.jpg|thumb|450px|Comp tooling]] | ||
Crane and Comp Cams sell cutters to machine the guide boss diameter using a hand drill. The arbor and cutters should be used with valve guides that are in good condition because the arbor uses the guide to locate the cutters. | Crane and Comp Cams sell cutters to machine the guide boss diameter using a hand drill. The arbor and cutters should be used with valve guides that are in good condition because the arbor uses the guide to locate the cutters. | ||
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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 ( | + | <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> | ||
==Rocker arm studs== | ==Rocker arm studs== | ||
| − | Production L31 Vortec heads come with pressed in 3/8" studs. For high performance and/or solid lifter applications, screw in studs are highly recommended. The pressed studs can be pinned, but this is a stop-gap measure that should be done only in cases where the spring pressures/engine RPM/lobe intensity will not be excessive and/or the budget is limited. Otherwise use ARP screw in studs or their equivalent. If not using guide plates, non shouldered studs can be used instead of studs having shoulders and a hex for tightening (this type of stud is tightened by "double nutting"). Screw in studs having a hex may require the stud bosses to be machined shorter to compensate for the hex. | + | Production L31 Vortec heads come with pressed in 3/8" studs. For high performance and/or solid lifter applications, screw in studs are highly recommended. The pressed studs can be pinned, but this is a stop-gap measure that should be done only in cases where the spring pressures/engine RPM/lobe intensity will not be excessive and/or the budget is limited. Otherwise use ARP screw in studs or their equivalent. |
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| + | If not using guide plates, non shouldered, non hex studs like Pioneer p/n 850001 screw in studs can be used instead of studs having shoulders and a hex for tightening (this type of stud is tightened by "double nutting"). | ||
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| + | Screw in studs having a hex may require the stud bosses to be machined shorter to compensate for the hex. | ||
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| + | ===Stud boss modification=== | ||
| + | If a hex stud is to be used, the stud boss will need to be shortened. The amount to remove varies depending on the stud being used; not all studs use the same radius from the hex to the stud. | ||
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| + | If a guide plate is used, add the thickness of the guide plate, the hex, and the stud radius together to reach the amount that has to be removed. This can be anywhere from about 0.320" to 0.375". The main consideration is that the rocker arm trunnion (if a roller rocker) or the rocker slot/pivot ball (if stamped steel rocker) doesn't bottom out on the stud radius. Check with the manufacturer for these dimensions if need be, otherwise the stud and guide plate can be measured with a caliper. | ||
===Guide plates=== | ===Guide plates=== | ||
Guide plates can also be installed at this time if desired. Consider Isky adjustable guide plates. Using guide plates will require the stud bosses to be machined shorter to compensate for the thickness of the plates and the hex on the stud. While home builders have successfully installed screw in studs without specialized equipment, unless the builder is well versed in doing this type of work, i.e. drilling straight, correctly located holes and tapping them, this is better left to a professional machinist/machine shop. At the least, a fixture to guide the drill bit and tap should be used. <br> | Guide plates can also be installed at this time if desired. Consider Isky adjustable guide plates. Using guide plates will require the stud bosses to be machined shorter to compensate for the thickness of the plates and the hex on the stud. While home builders have successfully installed screw in studs without specialized equipment, unless the builder is well versed in doing this type of work, i.e. drilling straight, correctly located holes and tapping them, this is better left to a professional machinist/machine shop. At the least, a fixture to guide the drill bit and tap should be used. <br> | ||
{{Note1}}If using guide plates, non self aligning rockers need to be used. If guide plates are not used, self aligning rockers MUST be used. | {{Note1}}If using guide plates, non self aligning rockers need to be used. If guide plates are not used, self aligning rockers MUST be used. | ||
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| + | {{Note1}}Hardened pushrods must be used with guide plates to prevent excessive wear. | ||
==Exhaust valve seats== | ==Exhaust valve seats== | ||
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