84 Z-28 305 4BBL (G) Engine I've owned since brand new. I went to drain the coolant from the block and removed the knock sensor. Not a drop comes out as there appears to be some sort of small expansion plug behind it and I'm afraid if I push it into the block while trying to remove it that I won't be able to retrieve it and it will float around and cause a problem. It is not just a build up of rust or corrosion as I tried pushing my finger through it and it is solid,, anybody else seen this before? I suppose I could drill a small hole into it and try and hook it out,,, just don't want to make a big mess of it.

 

No, there's no other plug up in there, it's just corrosion and schmutz.

That hole has been the block drain since 1955. Nothing changed when they started putting the knock sensor in there instead of a simple pipe plug.

Just poke it all out of there with a coat hanger or a screwdriver or something.

 

Be ready to move when you breech the crap build up in the hole. It's a gusher.

 

^ What they said. same happened to me, then it was raining green.

 

Thanks for all your replies,, got to say I've been working on Small block Chevys since the 70's and never had one where I could not push my finger through the crud,,, I'll give it a try this weekend again or some evening this week if I can find time.