Waiting for parts to do the upper and lower intake manifold gaskets project...

Have read several threads talking about installing brass 1/4" pipe plugs to block coolant flow to the throttle body, but so far threads located have not shown where the plugs are actually installed. Since parts have not arrived I have not started the disassembly and not truly intimate with the materials yet. What I have not solidified in my mind is exactly where the holes to be tapped are located. And does a bypass have to be created to make this blockoff work properly? Or point me to a thread I have not yet located.

I have located brass plugs having a recessed hex head and already have a tap. But I need to know what/where I am to tap and mount these plugs. What I can envision and what is actual are hard to decipher since I have not taken stuff apart yet to examine possibilities. A third question would be what type of thread sealant may be best to ensure a long term leak-free install (I tend to think Permatex #2 would be appropriate).

Appreciate a clarification before I get started towards the end of this week.

Additional searching indicates to me that The holes to be tapped are in the top of the lower intake manifold, which stops the water flow just before it would rise into the upper manifold. Correct?
The pictures I see of the lower manifold "look" like metal in the photos, but I understand they are really made of plastic -- that should make it very easy to tap. Sounds like I should do this mod while I have the chance.

No, the lower manifold is made out of aluminum. The upper plenum is a cheap plastic.

In this thread, you can see in the 3rd picture which holes to plug...

https://www.gmforum.com/mechanical-1...2005-a-304071/

When you remove the plenum and bypass hoses/pipes, does much coolant leak out - or just what'* left in the hoses drizzles out?

Mike, Thanks again for coming to my rescue. Parts should start arriving by Wednesday, with shipments from four locations. Weather cooperating (outside work area), I should get this up and done by this weekend.

One might lose about half a gallon if the system is not drained.

Ahh.. thank you. I wasn't sure if I would have to drain some off first.

Oh yes, you NEED to drain off as much as possible. Otherwise, a lot of it will end up down in the crankcase where you don't want it. If the lower manifold is removed, an oil change is required afterwards.

Why block the ports?

Studies have shown years ago, that if the upper plenum fails at the EGR port, without coolant flowing at the throttle body port, the coolant can't leak inside.

There is another option, but not exactly EPA compliant and requires a tuner.