Well, as a mater of fact I do have some idea. Most Arctic round shaft cl's come with (3) shims under the spider. Each shim is around .060" thick which will give you a total of .180". Some smaller and lower HP eng's come with (2) .060" and (1) .030" for a total of .150" . This is done to increase cl. engaugement rpm. They do this so they will not have to use a stiff dr. cl. spring to increase cl. engaug. How this works is when you remove shims the moveable sheave moves closer to the cam arms and this moves them back closer to the cam arm center of gravity. This will increase cl. engaug. rpm but the cl. will take a little longer to reach full shift out. We had to use this method alot when we were asphault drag racing. Hope this helps.
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