<VV> Holes drilled into piston crowns?!

[John McMahon]

First, I'd like to thank everyone who let me know that the valve stem 
diameter for Corvairs is 11/32"!

As I tear further into my 140 engine, I have discovered something strange. 
Each piston has a hole drilled in the top, near the edge, with a little 
channel carved out that leads from the hole to the edge of the piston.  The 
holes are about 1/4" in diameter, and about 1/8" deep.  Now, this might be 
"in the book" somewhere, but I've never seen it, nor have I ever heard of 
such a thing.  Anyone know what the story is?

Thanks,

John McMahon
1965 Monza coupe (with a spare 140 engine)