Cylinder head core plugs.

[RichardHawkins]

My cylinder head has plugs into the water jacket (core plugs) that are not the conventional disc type but are screwed in with a recessed square hole. The engine has been stood for 30years. I want to clean and inspect the water jacket. Has anyone removed these plugs? How is it done? What size and thread are they?

[billwill]

Ask Q.E.D. they seem to be using the same screw in plugs, judging by the video of their new heads.

[RichardHawkins]

Thanks Bill, I spoke to QED plugs are 3/8 BSP. QED advise heating the whole head, or drilling out. Having removed one plug by drilling it out until it was thin enough to collapse inwards, I have measured the thread as 3/8 NPT.