A little background first...

I broke my timing belt a month ago, shop said I probably had some bent valves because of a failed leakdown test. I sent head to machine shop, they said they found no bent valves, just some carbon deposits that were holding a valve open. I got my head back from the machine shop. They cleaned up the carbon deposits and checked the valve seating. I put the engine back together and when I was adjusting the rocker cleareance I noticed that one intake valve was not coming all the way back up. I manually turned the crank a few times and found that the valve did return to the top after being compressed a few times.

I fired the engine up once, and turned it off immediately ( I had the distributor 180 degrees off, doh! ). I opened the valve cover and found that that same valve had ejected the rocker arm. I think that it was sticking again and the rocker bounced off the valve since it was not following the cam properly. In the process it broke one of the 'ears' that positions it on top of the valve.

Now for my questions: Any idea why the valve is sticking? I thought the machine shop checked every valve for straitness but I need to verify that. Could it be a seal or a contaminant in the guide?

I need a source for used rocker arms. I found a local place that can get me a new one for $38, but I'm sure I can get one cheaper. I did a search, and found a member that has some, but am unable to IM or POST a message to this user because of my Trial User status.

Any help would be appreciated.