Engine noise...

[dadsgreentruck]

For a long time I've had a tick-tick-tick sound. Fairly constant in volume, but speeds up as the engine speeds up. I used to think it was an exhaust leak, but after changing the donuts and manifold gaskets, I don't think it's that.

Lately, it's got a more metallic ting-ting-ting to it. I picked up a stethoscope and listened around. It seemed to be coming from the passenger side valve cover. I took the cover off, installed my oil plugs and observed the valve train.
Tick-tick-tick coming from the area of #4. I loosened up #4 intake, then tightened it down until the ticking stopped, then 1/4 turn more. It seemed to have quieted down so I put everything back together and took it for a drive.

Don't here the sound at idle anymore, but I do at cruise. Definitely a hollow tick or ting sound. Kind of like the sound you would get if you tap a pushrod against a bench vise or something. I start to hear it around 40mph, and gets louder at cruise. If I accelerate, it gets quieter or goes away altogether until I take my foot off the gas, then it comes back. It also quiets down when I decelerate.

What could this be? Cam wipeage perhaps? It's driving me nuts!

Tim