1989 k2500 block coolant drain plug

[termite]

Good to know I will have to get a new plug before I attempt to drain. Just to be clear, removing low radiator hose doesn't drain all the fluid from the block correct?

Correct, there will be coolant remaining in the block even after pulling the lower radiator hose. A surprising amount the first time I pulled the drain plugs on a block.

 

[Caman96]

This:
GM Genuine Parts 14084945 Multi-Purpose Threaded Plug
https://a.co/d/1jq84BU

 

[PlayingWithTBI]

A surprising amount the first time I pulled the drain plugs on a block.

^^^this - here's an example of a 350 block on the engine stand being drained. Both sides need to be done.

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[Schurkey]

Good to know I will have to get a new plug before I attempt to drain.

Brass, or a brass draincock.

Just to be clear, removing low radiator hose doesn't drain all the fluid from the block correct?

Removing the lower hose drains the coolant to the level of the water pump openings on the front of the block. Everything below the water pump is still trapped.

There's another easy gallon left in the two sides of the block.

It's why it's such a bad idea to buy 50/50 premixed antifreeze/coolant when doing a flush--if you don't pull the block drains--and few people do--you've got a gallon-plus of flush water diluting what was "50/50" coolant; and in cold weather the freeze protection isn't strong enough.

This:
GM Genuine Parts 14084945 Multi-Purpose Threaded Plug
https://a.co/d/1jq84BU

He's already got a cheap steel/iron plug. He could just re-use it if he didn't care about future serviceability. I suggest a brass plug, or--better yet--a brass draincock so there's no chance of a steel/iron plug rusting in the iron block The brass won't corrode.