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Thread: Valve spring shim install

  1. #1

    Valve spring shim install

    I tryed install valve spring shims to my BBC head, Pro Topline 360cc. I have spring cups also. First idea was to put the shims under the cup. However, I noticed, that the cup will not center to the valve guide as well as if would put cup at the bottom and shims in the cup. I can move the cup more when the shim is under it. There is a small ramp over the guide that centers the cup better. The problem is worse with exhaust valves as the valve spring pocket isn't so deep as with the intake valves which center the cup better also with the spring pocket outsides. I have Comp Cams 4756 shims and at least Summit Racing webpage claims that they are hardened.

    http://www.summitracing.com/parts/CCA-4756/

    My shims aren't still that color, they are painted black. Also some shims showed little wear after few passes. They were in the cup. The black paint was ripped of some places and I could see bare metal from the shims. I had to take the engine apart on other reasons and I thought I'd move the shims under the cup at this time. I think that the cup is still harder material than the shims.

    So what's worse? A spring that can move more at the bottom with the cup or a valve spring chipping paint and metal from the shim?

    What centers the spring? The valve guide, the cup or both?

  2. #2
    Senior Member RACING JUNKIE
    Join Date
    Jan 2006
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    La.
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    2,890
    Shims should be inside the cup.

    JMO

    Zip.

  3. #3
    I think I figured this out. The exhaust pockets are quite shallow, about 0.1". So with 0.060" shim I'm already using the most of the pocket and the cup is starting to dance more and more the higher I'll lift it from the bottom of the pocket. Intake pockets are much deeper. So my options are:

    -Shims in the cup
    -Accept more assemled hight and lower spring pressure
    -Get retainers that will eat up the assembled hight more

  4. #4
    Senior Member EXPERT BUILDER gearhead1011's Avatar
    Join Date
    Jan 2004
    Location
    Shepherdsville, KY
    Posts
    313
    Quote Originally Posted by triniemi
    I think I figured this out. The exhaust pockets are quite shallow, about 0.1". So with 0.060" shim I'm already using the most of the pocket and the cup is starting to dance more and more the higher I'll lift it from the bottom of the pocket. Intake pockets are much deeper. So my options are:

    -Shims in the cup
    -Accept more assemled hight and lower spring pressure
    -Get retainers that will eat up the assembled hight more
    -use + 60 locks. For around 25 bucks they are a lot less $$ than the retainers.

  5. #5
    Senior Member DYNO OPERATOR
    Join Date
    Jan 2004
    Location
    central Illinois
    Posts
    459

    valve

    There are at least 2 different styles of hardened valve springs cups as far as location centering. If the cup has a wall/ring around the outside of the spring, it is meant to be located by the head materal outside of the cup. If this material is not tall enough to hold the cup, then look at the type that has the ring/wall to the inside of the spring. it is meant to be centered by the guide.

    In either case, the cup is hardened for the purpose of protecting the head from wear of the spring. Spring shims are too thin to withstand the spring even if they are premium materal and heat treated. That is why they should be installed under the cups only. Why take a chance they may or may not be eaten up and pass thru the engine oiling system?

  6. Racing Junk


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