The bolt that is currently in that location has no hole in it and it looks like a hollow bolt would be the only way oil could get to the rockers on my engine (235). I shot solvent into the hole for the oil supply tube shown in this picture:
[IMG]
http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Rockercleaning006.jpg[/IMG]
The solvent never exited anywhere until I removed the head bolt. Once I did, there was clear flow out of the hole shown here, which is where the oil tube under the side cover attaches:
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http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/Rockercleaning008.jpg[/IMG]
I triple-checked myself. With the bolt in place, there is no passage from the oil tube behind the side cover to the supply tube over the rocker shaft. When the bolt is out, the oil can flow.
I took the rocker assembly apart partly because it was very dirty but also because I haven't been able to adjust the noise out of it and I wanted to see what was going on. It turns out one half of the rocker shaft is destroyed, scored so badly I need to replace it.
I don't know anything about the history of this truck, so I don't know what was done/changed/replaced before I got it.
