Technical vacuum on an 8 ba

if you put duel 97 carbs on an 8ba where do you get vacuum source for the dist.

 

I don't use the vacuum advance on my 8BA but if I did...

 

If you've updated the carbs, you really ought to get one of them new fangled Chevy dizzys machined to fit the 8ba cover.

 

Or put a plate under one of the carbs that has a vacuum port on it. Those plates came in the South Wind heater kits for Fords.

 

This is more complicated than it may seem at first. The first assumption that I am making, is that we are not talking the stock "Load-A-Matic" distributor, but are referring to an aftermarket or converted GM distributor with a vacuum can. Both these "normal" types of distributor can function well using either "ported" vacuum (as in @Bandit Billy's post), or manifold vacuum. They will not work properly using the "venturi vacuum" intended for the "Load-A-Matic" unit.

Now, which to use? I have been a C2 Corvette enthusiast since I bought my first new one in 1967. I am a member of The Corvette Forum, an internet computer forum much like this one. Over there, there have been several discussions as to whether full manifold vacuum is better for performance than ported vacuum (which most corvettes are). The consensus is that it is, and ported vacuum is for optimum emissions, while full manifold vacuum is better for performance. Once that choice has been made, there are also discussions on different vacuum cans. I think a little research on what works and doesn't for the Corvette guys might be in order. Here is a link to a typical thread : https://www.corvetteforum.com/forums/c1-and-c2-corvettes/4934592-timing-vacuum-advance.html.

As I am partial to the looks of the old Mallory Flattop dual point units, I run mechanical only with no vacuum. It seems to work just fine. As for my current Corvette? Since it is a "matching numbers" original, everything remains as it was from the factory. It runs and drives just fine, but I am getting annoyed being "dusted off" by current batch of turbo 4-bangers.