Well working on the exhaust I noticed the block has a 90 degree petcock drain on both sides of the engine. What size is the petcock threads? I would rather get a spare before I try to remove this.

I see 1/4", 3/8" and others.

Any idea of the size? Maybe the same as the radiator?

 

Guess no one knows. Well seems like I got to figure it out myself as usual.

 

I removed the block drains from the 6.9l IDI in my Ford F250 and installed petcocks I found at the hardware store. It's a PITA removing the existing drain plug or petcock and running to the hardware store, but that's a sure fire way to avoid getting the wrong part.

 

Petcocks opened easily and I easily drained the block and re-filled it. Coolant was actually real clean.

They look like 1/4" on the threaded side.