What's up with this plug?
 

After pulling my stock heads, I see this plug in one of the coolant openings in the back of the head. It's like this on both the drivers and passengers side heads. The same opening on the front of the head is open. Obviously this is stock design from the GM factory, but do I have to worry about it before I install my AFR replacement heads?

you got me on that one bro. I thought those were the openings for the coolant pipe? If they are, then the back should be open. Although, some people close the back side of the coolant plugs and have no problems. I would ask a performance shop about this, or just PM them Your thread. Either way, keep us posted.

Thanks for the response. Not getting many hits on this thread so i'll do like you said and check with a local shop.

You got plenty of hits, Just not anybody that knows what that is on your block. PM this thread to Jon @ texas speed. He is always pretty helpful and might tell you what it is.

Good luck

I don't recall seeing that on anything I've taken apart....

Thanks all for taking a look.. I got my answer from Anthony at LG Motorsports here in Garland/Wylie. Below is what he told me via email.

Henry,

It isn't a plug that is the deck surface of the engine. If you ever have it out or look at a stock block there is nothing below it...so it isn't a plug it is just that it does not go anywhere.

I would assume GM just did the heads so there was one casting and not a left and a right so it was blocked off in the gasket.

Anthony
LGM

good to know