Is valve spring shimming needed?
11-02-2011, 03:39 PM
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Is valve spring shimming needed? I'm gonna be installing a set of pac 1218's in a couple of days and i will check the installed height when i do them, but are most people having to shim them or just install them straight up with no shims?
11-02-2011, 06:14 PM
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When I did PAC springs in my LS6, the installed height was ~1.778". Service Manual says it should be 1.800" ... and believe if they are within +/- 0.025" your OK. A 0.025" difference with PAC 1218 or 1518 springs equates to about 7 lbs of force difference with valve closed and about 8 lbs at valve fully open. Really not much to worry about IMO.
11-03-2011, 07:53 AM
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With higher lift cams, the general consensus is that you want to shim the springs to within .050 of bind in order to minimize oscillation of the spring. After installing my Pac .675 lift springs unshimmed under the assumption that my cam would be a ~650 lift cam, I've since gone with a cam that's got less lift, and TSP has recommended that I shim them.
11-03-2011, 01:16 PM
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depends what your looking to get out of them, longevity, control, etc. if you need shims let me know i have an extra set still sealed new i wanna move as i went with duals.
