Nuub here, so this may be alll wrong. 13b bridgeport/Holley 670 TA. So I think I need to run my 1" carb spacer in full plenum mode so I can get fuel to all four ports hopefully resulting in better throttle response. However, if I run the spacer in rail mode i think i would get twice the vacuum and easier starting via 50% less airspace to move(same vacuum pulling on 2 rails instead of 4). How can I get the benefits of both setups? Whacky idea: Could I install a 4bbl butterfly plate from another carb between the adapter and manifold, completely remove the primary valve plates , connect the secondary butterfly valve plates to a mechanical choke type cable. By opening or closing here , hopefully simulating either full plenum or half plenum configuration ? Whacky the right word?? Did i mention nuub here. Go easy on me plz.

 

When you go to a plenum, you need to completely recalibrate the carb. BTDT.

And high overlap rotaries do not run well at all with a plenum. Also BTDT.

The best bet is ITBs that are sized large enough to not be a restriction and call it done.

Plenums hurt, not help, throttle response, since the vacuum signal gets damped out so much.

 

Tried it. Doesn't work.