Engine block drain plugs?

They are usually plugged shut with sludge deposits. Take a pick or drill bit to clean the hole out to drain the coolant...

The thread size is determined by the definition of "1/4 NPT"

Stand pipe thread

tufcj wrote: I like to find plugs that have an Allen head. Makes them much easier to remove down the road. Bob tufcj

Bob, do you mean a hex head or a socket head?

!/4 national pipe thread is the tap you need to clean up the threads.
A square head 1/4 pipe plug will work just as good, but usually one finds them with a 9/16 hex head.

Brass plugs are OK, but if you over tighten them, and use a sloppy wrench to remove them, you'll round off the corners of the head. It's bad enough with steel plugs.

The Ambassador of plugs however, is an anodized aluminum plug with a hex socket head.

People tend to over tighten the plug, don't do that.

Teflon tape is more than adequate for a sealant. Less messy too.

old plumber here......


Edited by White70JavelinSST - Jan/19/2017 at 4:27pm

tufcj wrote: Hex head, like these: pipe plugs Bob tufcj

Gotcha.  I've never seen that term used for a socket head plug.  Learn something every day!