I have not been able to I.D. this plug in my service manual. , on the driver side of the block at the back of the engine. 22mm bolt head. 

Is this a coolant drain plug? instead of a freeze plug?   Also notice that inside it seems to be completely filled with junk.. ;-(

Thanks.

 

Yes, this is the drain plug. It should open into the coolant passage, so clearly there is a lot if sediment and debris to be cleaned out.

pop the freeze plugs and use a pressure washer to blow out the crud - if the head is off you can aim the stream down the water jackets as well. be prepared for a lot of crap to come out, and you will feel much better knowing it's clean afterwards.

You have it out of the car, why not take it to a machine shop and have it vatted?  Have the bores honed too.  I had a 2.4 block done a few months ago, $75 for everything.  

That's what I thought . Thanks for the info and advice.