Pros & Cons of vacuum vs. mechanical secondaries?

Gas mileage consists of a few things and one’s build may not be suited to it no matter what you do, but, in the end, it really is a state of tune of the carb, easy breathing in and out, a complete burn and most importantly…… a light foot.

Of course things like engine size, camshaft size and gear ratio are going to limit what can be done per gallon, but getting the best of what ever you have should be what your after no matter how hat the combo is.
OK - race vehicles may not care…

The pro’s and con’s? Hummmm ….. that’s a bit like splitting hairs. On a mechanical secondary carb, I will stick with the Holley DP as the example, the above complaint of to much throttle when cold has happened to me but that was short lived as you learn that curve real quick. IMO, it’s just a minor hinderance for a minor amount of time.

On a VS carb, it has to be getting the opening of the secondary side timed right and full open at its earliest without issues. That’s right foot controllable with a DP carb.

After that, it’s splitting hairs. Nothing to complain about between them. I find the VS a good carb to use on anything except a racing vehicle or a serious street machine. The higher end of performance. And just the flip for a mechanical secondary carb. Like said above, no sense of one on a car that’s a mileage master. But ether carb will work on ether end of the spectrum. Just not as great as it could be.