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Old 08-20-2007, 08:22 PM
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Umbrella Seal Clearance inside Valve Spring

working on a SBC and was just wondering what kind of clearance I need between the inside diameter of my inner valve spring and the outside diameter of my umbrella seal. thank you!

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Old 08-21-2007, 06:03 AM
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There was a thread on that a few months back here. I think it was Tom ? that runs a engine machine shop; said to use "studebaker V-8" valve seals so you don't have to machine the heads for clearance.
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Old 08-28-2007, 01:55 PM
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Thanks for your reply F&J

Let me elaborate a little more on my setup. My guides are already machined to accept a small diameter positive valve stem seal. My valve springs fit over these nicely as well. The problem lies with the exhaust valves since I am going to run rubber umbrella seals on them to allow some oil down the stem. Intakes are gonna have the positive seals on them.

The problem is, I can't find any umbrella seals that will fit inside my valve springs without rubbing on the inner spring. I would think that they would come apart pretty quick from the friction if I installed them like this.

So I was thinking of using a positive style seal with a smaller outside diameter that will fit inside the spring, but I'll remove the metal rings from the seal so it can't grip the guide. I would imagine if I did this, the seal with travel up the valve and stay in that position to act as a normal umbrella seal. What do you guys think?

Thanks a bunch
Dave
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Old 08-28-2007, 06:17 PM
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Never had this problem because I don't use umbrellas. If I did, I'd machine the spring pockets and use a larger diameter spring for clearance.

With positive seals, I use a very small, fine tooth triangular file and make a shallow cut on the inner diameter at one or two places to allow a little oil down the valve to lube the stem and guide.

I'd say that in a perfect world, your idea of using a positive seal without the guide boss clamp would work. But it's an imperfect world and I can see the valve angling around enough to catch the edge of the seal on the guide boss and push it up on the valve, where it will stay for the remainder of its tenure.
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