[jhirasak]

Texasdoc,

For Holly carbs with vacuum secondaries, you want the lightest possible spring that does not cause a bog. That is why they recommend that you keep replacing the spring with progressively lighter ones until you actually can feel it slightly bog as the secondaries open. The slight bog indicates that the secondaries opened slightly too early for optimum performance. By replacing that spring with the previously stronger spring, you maximize the performance of the carburetor over its full operating range. Holly spring kits are readily available and this is an easy task to accomplish.