Installed Height valve spring shimming- How much is too much?
03-11-2015, 09:08 AM
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Installed Height valve spring shimming- How much is too much? Hey guys,
Needing some advice on Installed Height.
Looking to setup a set of what I believe are BTR .660 springs for use with a custom cam. They are being installed in a set of 317 heads, and expected to run a max of 7000rpm.
My machinist put the springs on his spring tester and they came up with a very healthy 180lbs @ 1.800 and over 400 at 1.040, reaching coil bind at 1.025"
My cam is .610" Intake/ .596" Exhaust. Using the method of Coil Bind (1.025) + Clearance (.060) + cam lift (.610/.596) I come up with an Installed Height of 1.695"/1.681"
Just wanted a second opinion of this, as it's a fair amount of shims.
Also what is the general consensus on LS7 Lifter preload? How far past zero lash?
Needing some advice on Installed Height.
Looking to setup a set of what I believe are BTR .660 springs for use with a custom cam. They are being installed in a set of 317 heads, and expected to run a max of 7000rpm.
My machinist put the springs on his spring tester and they came up with a very healthy 180lbs @ 1.800 and over 400 at 1.040, reaching coil bind at 1.025"
My cam is .610" Intake/ .596" Exhaust. Using the method of Coil Bind (1.025) + Clearance (.060) + cam lift (.610/.596) I come up with an Installed Height of 1.695"/1.681"
Just wanted a second opinion of this, as it's a fair amount of shims.
Also what is the general consensus on LS7 Lifter preload? How far past zero lash?
03-11-2015, 10:03 AM
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For 7000 rpm performance, I shim to .050" less than coil bind.
03-11-2015, 10:16 AM
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Those springs shimmed to 1.750" have turned 7500 rpm in many different boosted setups and is the shortest installed height that I would recommend.
His tester may be a little off on pressure, it happens.
Only in endurance applications where 10,000 miles or more are expected does excessive open spring pressure potentially cause issues with valve tip wear.
His tester may be a little off on pressure, it happens.
Only in endurance applications where 10,000 miles or more are expected does excessive open spring pressure potentially cause issues with valve tip wear.
03-11-2015, 04:40 PM
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Forgot to note these are custom LS3 valves turned down to fit.
Thanks Brian, will do. I think I've ordered half my engine from you, and just placed another order last night!
Thanks Brian, will do. I think I've ordered half my engine from you, and just placed another order last night!
