Is there any value in using a carb spacer a carb style single plane port EFI intake? Particularly when using with a 4 barrel TB? You know the popular ones like the the "Super Sucker" and the 1" to 3" phenolic plastic ones. Some with four holes under the TB openings or some just open space.

I know they suppose to aid in increasing the air velocity and increase the vacuum signal in carb applications but would they help us in port EFI applications??

I think of using them on a carb style single plane on intake a 396 cu LT1.

 

Only to increase plenum volume ( open spacer).

 

It would make the runner longer.

 

The single plane EFI plenum is below (and above depending on the conversion) the spacer so it would not function to increase runner length.

Unless you are running a 4 barrel EFI throttle body directly where the carb would mount, I would just use the correct open spacer.

 

If you can fit one, use it. Single plane manifolds tend to have smaller plenum area. The spacer helps this. I was able to get a 1" under my Edl Victor EFI.