Oil Gallery plug thread

[Lesterz]

I have pulled the engine out of my New Major & I am trying to clean out the oil gallery but cannot remove the square headed brass plug at each end of the engine block ((Part # 358063-ESD Plug (Cylinder block oil gallery)-standard)). I have tried a few gentle taps with a hammer on the plug to loosen it but I am not willing to put too much effort into this as I might damage the block. It appears I may have to drill them out & retap the hole. Does anyone know what thread size & type/pitch these plugs might be? I do not want to stuff up the hole. Thanks.

[super6954]

To Be honest I tried to remove those once and never got them out .Ive re built loads of majors and just flush the blocks good with de greaser blow them out with air and re build them. Ive never had a problem with any returns on my work . I would not worry to much about removing them unless the blocks full of sand or something else it's pretty hard to get 100% clean in an old block .
Somebody will probably jump up and say I don't know what I'm on about and start a 2 page discussion on my answer but thats what i do.
I guess the threads are an imperial or standard (BSP) pipe thread the ones in the head are and maybe 3/8 from memory.
Regards Robert

[Dandy Dave]

I've had times where I have heated the stuborn plug, Let it cool, and then they spin right out. If the engine you are working on has had metal filings go though it, it is a good Idea to be sure the oil galleys are clean. If the engine is just tired, then removal may not be necessary. Just clean them good like Lesterz Z said. I've used carburetor cleaner in a spray can in the past. You will see the black stuff come out. Dandy Dave!