Well, this afternoon, I took the push rod cover off and started the investigation. Here is the oil tube to the rockers:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage001.jpg[/IMG]

I removed the tube and it had no oil in it. Then I used compressed air to make sure the drilled out head bolt was clear, and also the passage in the head:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage007.jpg[/IMG]

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage010.jpg[/IMG]

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage006.jpg[/IMG]

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage005.jpg[/IMG]

Once I was sure all these passages were clear, I went after the spot I really suspected: The rearmost fitting for the oil tube:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage012.jpg[/IMG]

Here is what I found:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage016.jpg[/IMG]

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage019.jpg[/IMG]

There didn't seem to be much sludge in the fitting itself, but you couldn't see clear through. Here it is after cleaning:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage017.jpg[/IMG]

Here is the hole after cleaning:

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Blockage021.jpg[/IMG]

So the hole was about 90% blocked. I'll put everything back together tomorrow morning and see what happens.

1956 Chevy 3200