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Question about valve shims.

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I'm sure im just misunderstanding something but if your valves are too tight how does adding a larger shim put them back in spec.?

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Valve measurements refer to the gap between the bucket and Cam lobe. Tight indicates that the gap is less (smaller) than the specification. Valve shims are used to fill the space between the end of the valve stem and the bucket. To increase the gap a thinner shim has to be used. Hope that helps put a picture in your head.

CoKTM

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ANd the wear on the valves is on the end of the stem. IE the stem gets shorter, thus the cam lobe pushes the valve up but it opens less.

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I thought the valve wore into the seats taking away all the clearance. This is why they tighten up.

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I thought the valve wore into the seats taking away all the clearance. This is why they tighten up.

This is correct, the valve faces and the seats wear. This makes the valve sit higher up in the head, thus decreasing your clearance and requiring a smaller shim to get the correct clearance back again.

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Ok i get it now. I was watching a video and it was a case where the clearance was to big :smirk: . So when the valves tighten up this causes them to stay pushed against the camshaft, thus leaving them slightly open creating the hard starting effect?

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Ok i get it now. I was watching a video and it was a case where the clearance was to big :smirk: . So when the valves tighten up this causes them to stay pushed against the camshaft, thus leaving them slightly open creating the hard starting effect?

Pretty much.

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ANd the wear on the valves is on the end of the stem. IE the stem gets shorter, thus the cam lobe pushes the valve up but it opens less.

Well, not really in most cases on a modern engine.. the valve face and seat wear, then the valve recededs into the head, the stem "moves up" and the clearance gets tighter.

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