worried about cams

[Fizzer]

I've recently had my cams out (2ltr blacktop zetec) and back in again and have just been for an hour long 'brisk' drive round the berkshire downs.
When we got back I lifted the bonnet to have a listen and see which bits were falling off when I noticed that there was a noise which appears to be coming from under the rocker cover. Not a screech, more of a rubbing sound. I was careful to use graphogen assembly compound (recommended by Ken at Newmans) on all the bearing surfaces.
Is it possible I've overtightened the bearing caps? What else could it be?

I'm going to whip the top off and have a look this evening, any pointers on what to look for would be gratefully received. Is there a surefire way to check the bearing surfaces?

Cheers

Andy