Power valve removed from a Holley 3259-1 carb question

[6s1640]

Hi all,

A few years ago I  purchased a 715 cfm Holley 3259-1 with date code 612 for second week January 1966.  I am having it restored, but before I sent off,  I disassembled to make sure the insides were complete and/or there were no surprises.  What has me curious is the power valve I removed.   It does not have the usual spring and valve.  It appears to be a plug but does have holes below the threads that might allow fuel to flow.  From the plug power valves I see on line, they have no holes.   Attached is an image of that power valve.  Please help me understand the intent of the version of power valve.  Is it a plug or does in just allow more fuel to flow regardless of vacuum?   Also, there appears to be a rivet in the end.  Was it a standard power valve and modified?  Was this rivet part of the original piece or was it added for additional affect?

Thanks

Cory

[98SVT - was 06GT]

They all have a hole in the side. Homemade plug. http://www.manciniracing.com/hopovaplandg.html
From a Chevy forum: One reason for blocking it off is for consistancy in a drag race engine. There are some conditions depending on cam, exhaust etc where the PV could be starting to close at high rpms under load, like at the finish line at the drag strip. This is one more thing that can affect consistancy, which is far more important than top speed in bracket racing.