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Message: [QUOTE="TARM, post: 109361, member: 578"] Here is the link to the [URL="http://www.compcams.com/Base/pdf/ValveSpringChart.pdf"]Comp Cams Valve Spring Specs Sheet[/URL]. The 910 is on page 3 of 6 on the right #910 Here is the specs and needed info: Here are the specs for the 910 striaght from Comp cams: Base install height: 1.850" Maximum Coil Bind Height: 1.280" Inside / Outside diameter: 1.354" / 0.940 Spring Rate: 415 lbs Install height : lbs 1.900" : 72 lbs 1.850" : 92 lbs 1.800" : 113 lbs 1.750" : 134 lbs 1.700" : 155 lbs 1.650" : 175 lbs 1.600" : 196 lbs Factory install specs: Install height: 1.810 Factory seal integral shim .045" Spring install height with seal: 1.76" Cam .410" Max Coil Bind height: 1.28" I would recommend simply following the above install heights for the Comp Cams 910s as well that will give you a 130lb seat pressure. IMO between 1.750"-1.760" including seal and 1.800"-1.810" with out seal (measurement goal for use with micrometer) This will get you seat pressure between 130lb-134lb. For reference here is the stock OEM spring specs new: Closed Seat Pressure @ 1.76" = 110 lbs Open Pressure @ 1.35" = 250 lbs 350lbs per inch rate A few stock springs had been tested that had 100K miles on them by individuals that posted the findings and seat pressure was found to be reduced down to barely 70lb at that point. Thus you can see the issue and why these springs were considered soft. The shims I recommend are from Jegs. They come in a multi shim thickness kit [URL="http://www.jegs.com/i/JEGS+Performance+Products/555/20591/10002/-1"]JEGS Valve Spring Shim Kit #555-20591[/URL] Valve Spring Shim Kit 1.437" O.D. 0.645" I.D. Includes: (16) 0.015" (blue tempered spring steel) (16) 0.030" (case hardened steel) (16) 0.060" (case hardened steel) If you want to do the most accurate job of shimming back to a specific height such as factory spec then I recommend purchasing 2 packs that way you can combine two or more as needed to get the proper height for each valve. This way you could combine a 0.015 and a 0.030 if you needed 0.045 to reach proper seat height spec. Or most any combo you might need to get you close enough. From what I have seen and given even minor amounts of cam and valve train wear and the max coil bind height of 1.28" and that is the max it can be and mine all measured lower. You could set your seat range without binding issues and a safety margin between 1.74 - 1.76 For every 0.01" of height compression pressure increases by roughly 4.1 lbs 1.74" = 138 lbs 1.75" = 134 lbs 1.76" (stock height spec) = 130 lbs I also recommend getting the Proform micrometer from Jegs as well as its not to costly and has a decent range that covers both above and below 1.800" which IMO is needed. [URL="http://www.jegs.com/i/Proform/778/66902/10002/-1"]Proform Valve Spring Height Mic 66902 JEGs#778-66902[/URL] This should give you all the reference info you need to do the springs accurately and to the correct seat heights. [/QUOTE]