Re: Untitled

Bert:

If you do some careful measuring, I think you will find, as I did years ago, that the secondary throttle shaft is offset slightly. Why, you may ask? Well I did some thinking about that, and even checked some Holley carbs, and found the same thing same to their 4150, 4160, and and I came to the conclusion it was done in the interests of safety. The shafts are offset in such a way that intake manifold vacuum will tend to hold the throttle plates shut. The fact the shafts move freely when the engine is off demonstrates this. When you floor the accelerator pedal, intake manifold vacuum drops, freeing the secondary side, and allowing the vacuum servo to smoothly open the secondary throttle. When the pedal is released, and the carb linkage closes the secondary throttles, high intake manifold vacuum again helps keep them closed. If anyone out there has ever placed a carb on a flow bench, and varied the pressure drop below the throttle plates, you will find the effort to open the secondary throttles also changes.

Give things a measure, and if you can, try the flow bench test. You'll see what I mean.

Don