Found it: cam gear wear

I got my cam gear off and there was wear on the back where it had rubbed a bolt. That’s probably the noise.

 

The less good news is someone pointed out that the back of the gear looked off and apparently I had forgotten the thrust bearing this one is supposed to use and that’s probably why it walked back a bit. 

Worse news is the cam bearings are absolutely trashed. That means engine out to replace them.

After feeling an appropriate amount of sorry for myself I managed to get the heads off to inspect further. I had seen a little scoring on the boroscope and I was afraid it meant I’d need to rebore the engine as well. Machine work meant it might be worth it just to move to a ls3 now. Luckily with the heads off I could inspect and you can’t feel it at all. A little dingleberry hone and it’ll probably be more than fine.

The cam had 5 damaged lobes and I have 5 damaged lifters. Can you guess the one I was hearing?

Engine is just about ready to be removed now. I need a crane and stand. Hopefully I can borrow one locally. 

Luckily the heads still look in great shape. Whatever went down with the cam left them untouched.

I guess I get to learn how to replace bearings, and put in rods and pistons. I might be able to get away with just reusing them, but everything is coming apart for bearings anyways and the stock rods are timebombs at 7k rpm.