[scottj]

Whether or not the 1:1 linkage will be better or not will depend on your combination.

Generally the lighter the vehicle, the lower the gearing, and the higher the power, more likely you'll benifit from the 1:1 ratio.

Since mechanical carbs are delivering fuel and air ahead of the engines torque curve, you have to properly match the delivery to how quickly the engine can use it (how quickly it can build rpm).

Vacuum secondary carbs deliver fuel and air behind the torque curve so fuel and air delivery is automatically matched to the engine's needs.

If your combination runs best (responds and builds rpm quickest) with a 1:1 mechanical carb, then a progressive ratio mechanical or a vacuum carb will "soften" throttle response and slow rpm build by comparison.

On the other hand, if your combo needs a vacuum carb, then it will run worse (poor response) with a mechanical secondary and worse yet (terrible response) with a 1:1 ratio.

In some cases with very high HP and limited traction, a progressive ratio mechanical or even a vacuum carb with its "softer" throttle response can aid in getting the car to hook up off the corner, where the 1:1 linkage will light up the tires.
Scott