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Do you normally only have to do the primary throttle shaft and NOT the secondary..



The 2ndary shaft does not take the abuse the primary shaft does. The wear is generally a result of the amount of use the primary shaft gets and the return spring tension. The net result is that the primary bore on the throttle lever side 'elongates' over time. The new bushing corrects this.

The 2ndary bore gets a little loose sometimes but since it does not have an idle circuit(unless it happens to be a 4 corner idle system like Holley double pumpers), you do not need to bush unless the 2ndary butterflies do not close completely.