Valve spring tech
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==Overview== | ==Overview== | ||
| − | This article will | + | This article will help the reader to get a grasp on the different aspects of setting up a valve spring for a particular application. |
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==Valve spring design== | ==Valve spring design== | ||
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###Circle track and moderate bracket racing 450-600# open. | ###Circle track and moderate bracket racing 450-600# open. | ||
###Serious drag racing and limited distance circle track racing 600# and up. | ###Serious drag racing and limited distance circle track racing 600# and up. | ||
| + | |||
| + | ==Measuring valve spring installed height== | ||
| + | The correct installed height is important to prevent coil bind and to have the correct clearance between the valve guide boss/seal and the valve spring retainer. | ||
| + | |||
| + | ===Using an installed height micrometer=== | ||
| + | [[File:PRO-66902.jpg|right]] | ||
| + | |||
| + | This tool fits in place of the valve spring. By extending the body, the measurement is taken from the side of the tool. This leaves your hands free and is accurate as long as the retainer-to-tool matches up correctly. | ||
| + | |||
| + | Care must be used to assure the mic is measuring from the same surface of the retainer as the spring bears on. If there's a problem with this, in some cases a shim can be used or a spacer made to compensate for any mismatch between the tool and the retainer. | ||
| + | |||
| + | The original [http://www.combo-flo.com/msp_hm.htm '''Hite-Mike'''] is available, as well as a cheaper alternative like made by Proform, [http://www.summitracing.com/parts/pro-66902 p/n 66902].<br style="clear:both"/><br> | ||
| + | [[File:Snap height.jpg|right]] | ||
| + | |||
| + | ===Using a snap gauge=== | ||
| + | Put a valve in the head, install the retainer and locks that will be used. Holding the valve tightly against the seat, use the snap gauge to measure the available installed height. | ||
| + | |||
| + | Once the available height is known, compare that to the valve spring installed height that is required to get the seat/open pressures needed for the cam to be used.<br style="clear:both"/> | ||
| + | |||
| + | ===Measuring without snap gauge or height mic=== | ||
| + | #A 6" to 8" length of small diameter welding rod or clothes hanger wire | ||
| + | #Wire cutters | ||
| + | #Caliper or 0"-2" micrometer | ||
| + | #Feeler gauge pack | ||
| + | #Bench-mounted vise | ||
| + | #A buddy on hand to help | ||
| + | #Bench grinder or hand-held file | ||
| + | #Needle-nose pliers | ||
| + | |||
| + | ;Procedure | ||
| + | *Using the installed height of the outer spring given with the springs, cut a piece of welding rod or clothes hanger wire to that length. Round both ends of the wire on a grinder, or with a hand-held file. | ||
| + | |||
| + | *Install a valve with retainer and keepers. Use a heavy grease to hold the keepers in place. Pull on the retainer while twisting clockwise and counter-clockwise slightly to seat the assembly, pressing down on the valve face with your other hand to prevent the valve from rotating. | ||
| + | |||
| + | *Hold the wire with needle-nose pliers and position it between the outer spring pocket and outer step on the retainer. | ||
| + | |||
| + | *Have a buddy use a feeler gauge to measure the gap between the wire and the retainer. This will tell you the shim thickness you'll need to achieve the correct installed height. Mark a single ring around one end of the wire with a felt-tip marker, to identify the wire later. | ||
| + | |||
| + | *Cut another wire to length, so that it fits between the inner spring pocket and the inner step of the retainer. Mark two rings around one end of the wire with a felt-tip marker. | ||
| + | |||
| + | *Subtract theoretical valve lift from installed height. For simplicity, let's say the installed height is 1.700" and the theoretical valve lift is 0.500". Cut a third wire to 1.200" and mark it with three rings. | ||
| + | |||
| + | *Place the outer spring in a vise along with whatever thickness of shims you determined you will need (within +/- 0.015" is close enough tolerances). Holding the three-ring wire with needle-nose pliers and the wire parallel with the spring in the vise jaws, compress the spring down to the length of the wire. | ||
| + | |||
| + | *Insert a 0.010" feeler gauge blade between the spring coils at 5 positions along the spring. If the feeler gauge goes in without interference at all positions, you're good to go with the outer spring. | ||
| + | |||
| + | *Measure the length of the two-ring wire with a caliper or 0-2" micrometer. Subtract theoretical valve lift. Cut the wire to this new length. Place the inner spring in the vise (no shims). Holding the two-ring wire parallel with the spring, compress the spring down to the length of the wire and repeat with feeler gauge. If it clears at all 5 positions, you're good to go with the inner spring. | ||
| + | |||
| + | *Disassemble the retainer/keepers. Install the correct shim thickness you will use. Reassemble retainer/keepers. Holding the one-ring wire with pliers on the spring shim/shims at the outer step, open the valve until the retainer outer step contacts the wire. This will place the retainer at the full valve lift position. Verify 1/16" to 1/8" clearance between the valve guide and the bottom of the retainer. If seals are installed, you're good to go. If seals are not installed yet, allow for their height above the guide. | ||
| + | |||
| + | *If the clearance is insufficient, different retainers or keepers (available in +0.050" size) can be used to correct it, or you can cut the valve guide bosses to correct the issue. An alternative is to use longer valves, just remember that using longer valves will alter the installed height of the valve spring. Most valves are available with stems that are 0.050" or 0.100" longer than factory specification. Adjust your shim thickness accordingly. | ||
| + | |||
| + | ==Correcting valve spring installed height== | ||
| + | If the installed height is insufficient (and depending on how much more installed height is needed), a +0.050" lock can be used. If even more installed height is needed, there may be different retainers that will give more height, or the valves may need to be replaced with longer valves. In some cases the valve spring seat can be machined deeper. Use caution/consult the manufacturer to be sure the seat can be made deeper without hitting a water jacket or port. | ||
| + | |||
| + | {{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. Rockers 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. | ||
| + | |||
| + | Mock up the assembly and check the clearance closely. In the case there's '''''insufficient''''' installed height, 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. | ||
| + | |||
| + | If it's found that there's '''''too much''''' installed height, there are a couple options: | ||
| + | *Use hardened shims | ||
| + | *Use a spring cup | ||
| + | *Use -0.050" locks | ||
| + | *Use "shorter" retainers | ||
| + | |||
| + | A tool to help determine the effect on installed height using different retainers and/or locks is the Howards Cams [http://www.summitracing.com/parts/hrs-92010 p/n 92010], shown immediately below: | ||
| + | |||
| + | [[File:Ret height92010.jpg]] | ||
==Resources== | ==Resources== | ||
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