Thank you to everyone that has responded, I did have time to pull the valve cover and didn't see anything obvious wrong, but I will perform a compression test when I have another day off. Hopefully it's just in the valvetrain.

I didn't notice that he had mentioned that it is a Gen VI. That being said, I do have a factory GM Gen VI 454 in my garage that has never been apart that came with a flat tappet cam, straight from GM. I bought this thing as a core from a plant here in town that used to rebuild / reman them for the dealerships. The place was called Hesco, and it was a pretty good sized operation back in the day. They had literally hundreds of old cores over there, and I found this one that looked like it had barely been started up and run - still had original bore, crosshatch in the cylinders, etc. Not sure what the problem was with it, but all the wrist pins are tight in it, which led to scuffing in the bores and probably poor ring seat. Still had all the GM gaskets, factory inspection marks, etc., so I don't think anyone got in there and switched things out. I'm not sure why GM would have built a Gen VI with a flat tappet cam, unless it was for some specific application - maybe heavy truck, industrial, whatever. Could have been a very early Gen VI that they put a leftover cam in, I don't know. Mystery to me, but he had several others there like it.

Have you actually pulled a spark plug to note it's burn condition? Vacuum leak at the manifold might explain ticking noise & running rough at idle, but doesn't coincide with the rich condition.

are you sure it is not a gen 5.i have never heard of a gen 6 with a flat tappet cam.what is the block casting number?

Mike, I'll have to look at the casting number at home tonight, but it is definitely gen VI - has the provisions for roller lifter retainer in the valley, and the 6-bolt alum timing cover, etc. Weird, huh? I think GM did some strange things with some of the heavy truck engines.

Capains Call exhaust? If so does the tick change with exhaust open vs. closed?

Don't rule out a spark arc from a bad wire. My friend called me with a ticking two years ago, bad wire arcing on the block. Engine ran like crap, and the arc was so loud I thought it was a lifter. Weird

my port has a ticking noise too, sounds like from the top. marina said probably either exhaust or valve. waiting on them to open it up. hoping it doesnt cost a fortune to repair.

Yes, it has captain's call, but the sound does not change when you switch it. I haven't checked the plugs, but will when I pull them for the compression check. I will check the plugs wires as well, but I doubt thats it. I'll try to post a video of it next time I work on it.

if it left the plant that way it is a rare bird.