Does anyone really do this to their cooling system?

volaredon said

If true you can bush the hole or find a petcock that directly threads in.
I'm thinking that the block drain is 1/4 not 3/8 NPT because the petcock I used also fits the radiator in my truck. Maybe it's a "different year" thing?
My current build is also a 74 block

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Yep, for the record its a 1/4" NPT plug. I just checked on my 1974 slant six block. Rusty and volaredon were right. Thanks to all who weighed in. I still think I'll just replace it with a square head brass pipe plug, as I don't like the look of a petcock coming out the side of my engine. But that's just me!