When my Camaro has been sitting for a few days (I'm in college and live on campus, that's why it sits that long), I'll get a tick on startup. It increases in frequency as the RPM climb, and then when the engine is warmed up, it goes away. Any ideas? The only thing I can think of is that it might be a lifter, but I can't think of why I think that, really. The car has 88K on it, and a 3.8. Any thoughts/ideas?

 

A couple possibilities are a gunked or gummed up lifter, or oil isn't making it up through the pushrod right away to lube the rocker arm.
Been there, had that, and changing to synthetic oil gradually cleaned out the crud in the engine (as it's known to do), and got rid of the noise.

 

I would try 69's suggestion first, your could get lucky and have a plugged lifter.

I had the same problem on mine and turned out to be a failing oil pump (which gm's in my experiance seem to have issues with them).

 

I'll definitely hope synthetic will clean it out first. SES light came on yesterday over an exhaust leak/O2 sensor.