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Old 01-10-2008, 06:01 AM
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Cam/Valvespring Confusion

As noted in another thread, I have a set of Summit brand aluminum heads and a Lunati Voodoo 60102 cam. I've been told that I will need to run shims regardless of spring height due to the nature of aluminum (valvesprings running directly on the aluminum is not good).

The confusion is about the spring pocket diameter. The spring pocket diameter is larger than the diameter of the recommended valvesprings from Lunati. There shouldn't be a substantial amount of clearance between the spring and spring pocket should there? I'm thinking that there should be a snug fit to prevent the spring from walking around inside the pocket.

Are there shims or spacers available to compensate for the differences in diameter? I've also been told that springs are available in the larger diameter. I just need to specify spring rate, height, etc. In other words: two springs with different diameters, but with the same specs. Is this correct? I'm sure the cam doesn't care what the spring diameter is, as long as it has X amount of pressure, etc.

Any help is appreciated.

Thanks,
300Deluxe

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Old 01-10-2008, 10:36 AM
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heads

I'll start off by saying that your looking for a spring locator, not a shim. People call them a few different names, like spring cups, or spring seats among others.

They make the spring locators in ID type and OD type.

The ID (or inside diameter) type locate off of the inside of the spring.

The OD (or outside diameter) type locate off of the outside of the spring.

You can use either one. you need to know the guide dameter at the base of the spring pocket, the inside diameter of the spring and the outside diameter of the spring. Call a cam company, not Summit or Jegs and give them the info and they will give you a part number.

If you can't get help PM me the sizes and i'll look them up for you.



Keith
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Old 01-10-2008, 11:43 AM
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Did you remove a valve spring and test on a spring tester to see what the actual closed and open pressures are going to be based on the actual installed spring retainer height?
Worst case you may have to swap the valve locks for some +.050" locks to increase the valve spring installed height and reduce the running spring pressure.
A lot cheaper than new springs and new spring seat locators. Many good machine shops have these +.050" locks (Crane, Pioneer) in stock for fine tuning spring height and pressure.
They are available in + .050" and -.050" to adjust the installed height and 7deg or 10deg type.

Last edited by F-BIRD'88; 01-10-2008 at 11:50 AM.
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Old 01-10-2008, 11:47 AM
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Thanks for the suggestions guys. I'm gonna dig into it and see what I can find out.
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