Take a piece of vacuum hose or a stethoscope and put it up to your ear and the other end to were you think the sound is coming from. You will be able to tell dead on.
OK, my results. Not as good as I hoped, but still good.
I'm not sure if the header bolts were loose, but they definitely weren't torqued to spec (22-45 lb-ft). They came loose WAY too easily. I loosened each one, then retightened each to about 35-40 lb-ft. Then started the car.
The same ticking noise was there, but it faded away after several seconds. I revved the engine several times, but I could no longer hear the noise. Weird.
A few weeks earlier, I had put in an oil additive to try and clear out any plugged roller lifters. The car's been sitting since then, so I suppose it's possible that could have affected the noise. I also haven't restarted the car since this test Saturday.
Could I still have a leaky header gasket? Or does this sound like a stuck roller lifter?
I started the car again last night, and the ticking noise is back just like always. So, it's not an exhaust leak. A friend of mine mad an observation last night that I had missed - if you hold your hand on the intake manifold, there's a light tapping noise that can be felt. I must have some slack in the valvetrain, or a collapsed lifter. Suckage.
I'd be happy to just rebuild the top end and replace the lifters, but my oil pressure guage has always read low. I know the stock guages aren't accurate, but it does worry me. I'm concerned that the oil pump is dying. Does it sound like I'd be better off rebuilding the entire engine, just to be safe?