BBC threaded hole in block - what goes here?
 

This picture shows my 71 402 that I will reinstall in my Impala this weekend. It has been out of the car so long that I can’t remember what went in the hole shown at the left side of the picture. Any thoughts?

Might be a return port for an external oil filter/cooler ? Just a large plug in the engines I find on line.
Well, this is in a different location on the block...

https://www.yenko.net/forum/cache.ph...x%2Fs-l500.jpg

Mounts the ball stud for the clutch cross shaft (Z-bar) on a Corvette, and maybe others.

Duh, I can’t believe I didn’t make that connection. I would have thought that boss would be spot faced and drilled/tapped, surprised it’s as-cast.

I don't think the large threaded hole above the freeze plug is for the zbar. The machined surface just in front of the oil filter area is one of the pivot locations. Most BBC have another one on the other side of the filter area (right next to the bell housing flange).

Check and see if that larger hole isn't pipe thread.

I could be wrong. Been a lot of years since I worked on a BBC.

This.

'67 427 Corvette...

The hole in question is a 1/2x13 threaded blind hole.

Thanks for showing. What are the other two holes for?

Chevelle Z-bar uses the hole near the bell housing. Early blocks don't have the center hole, so??

Thanks guys! I didn’t realize the corvette had the z-bar pivot in a different location.