Hello to all new here can help with this question .yes they are pressed in they have a special glue and the end that goes in to the block is slightly wider this is why they need drilled out ..once these tubes are pressed in they are heated to seal them.but caution must be taken when doing so or the whole project will be scrapped..for race projects i block this because most of these dont go anywhere its a closed vacuum port .but for stock apps its needed for other things to work..if you already have this tube out and everything is ok then cool ...if not then this is what i would do...after you take the metering block off. (Course youll need new gaskets .metering block gaskets can be bought through holley .car quest.auto zone etc.).So take and leave the old gaskets on then place into a shop rag or towel and put in your vise making sure its in there firmly .also looking up at you .the ideal set up would be a drill press but not everyone has this fancy item.take a drill bit smaller then tube see how far it goes before bottoming out.i use thread or dental floss to wrap around bit so to tell me how far.this way when im pressing new tube in i dont go to far.with a tap ih a fine thread count tap the hole making sure you have a screw that fits tap.note dont thread the hole tube thread about a 1/4 so when screw stops,and you tighten just alil more it will start to stretch old tube .now with alil heat to srew and a small claw hammer and a piece of wood remove screw should slide right out,be paitent it will come out if it doesnt then it will need drilled out.after its removed clean out with carb spray,and blow out with compressed air.reinsert new tube i use alil indian gasket sealant on tube going in block to help seal it.hope this helped....Dennis "carb".
