Top end noise

I take my car to the alignment shop yesterday and it drives and sounds great. I go to pick it up today and the guy says that there is a clattering in the top end, I listen to it, and sure enough it's there. I already broke in the engine for the 20 minutes at 3000rpm and then 10 minutes at 2000rpm and drove it to the alignment shop with no problems. But now there is a noise that is bad enough to have to tow it home. I'm thinking that it's valvelash, but I have no idea how to fix that with the rocker arm assembly since it's not adjustable. Here's my build as far as heads and valvetrain go:
1.88 int
1.60 exh
stock 318 72' heads milled 20 thou
stock rocker arms
purple shaft 340 specs cam
purple shaft lifters

ANy help is greatly appreciated.

Jake