This is a short description of the mods.
For more info see the petcock mods for the GT-series petcocks: viewtopic.php?f=9&t=14743
The passages are smaller in the T-series petcock. Used a 10-24 set screw & tap.
Screws smaller than 1/4” are given a number size. #10 is .190” & 24 is the thread pitch.
The screw is a bit loose, which gives some room for the JB Weld.
Pic of the installed set screw. Make sure the set screw is recessed & meticulously clean up any JB Weld.

Pic of the modified filter bowl. It’s ok if the set screw sticks out.

It’s necessary to remove part of the selector so that it clears the vacuum chamber.

Modified petcock in the on position. Down is off & up is reserve.
Marked the off position as a reminder that this is a manual petcock.
