454 drain plug size

[pschauss]

I'm thinking replacing the drain plugs on my 454s with hose bibs to make it easier to drain the coolant. What is the thread size?

[JeremyD]

1/2" -20 thread

Eddie Marine makes a nice oil drain kit
https://www.summitracing.com/parts/edm- ... cgQAvD_BwE

[pschauss]

Not NPT?

[Tony Meola]

Peter

Why not just pull one and just get it matched up.

[S Ritzert]

1/4" npt unless its been tapped to a larger size. about the mid 90's mercruiser went to a blue plastic drain plug, I'm not certain on that thread pitch, but the brass that goes into the block is still 1/4 npt. Volvo also used a blue plastic plug that is a different pitch than mercruisers about the mid 90's. regardless, the actual thread into the block is 1/4 npt.