Timing belt replacement disaster

[Y33TREKker]

LOL...yes....I pulled the pin. The tensioner had plenty of force on the pulley so I am 99.9% certain that its good. What has me confused it that the sound is rapid like you would hear from a lifter even though this engine does not have lifters. In my experieince a rod knock is a deeper sound and less frequent. Just for giggles I am going to pull the serpantine belt this weekend and verify its in the engine and not an accessory.

Our engines do have lifters, but they are solid (not hydraulic) shim in bucket style lifters that have to be checked and adjusted from time to time.

Adjustments are done simply by measuring the clearances of the current shims, then replacing the current shim with another slightly thicker shim that has the correct additional thickness to take up any extra required clearance as measured.

It's the same type lifter setup found in many motorcycles.

Hard to say for sure though, since I also saw a Youtube video where the problem ended up being a valve cover gasket that was leaking, and I'd swear that noise sounded very similar to the one in your video.

[Makocross]

It sounds like a blown exhaust gasket. It is easy to check before you do something expensive. Start it up and before it gets hot feel around the header to exhaust joint and the header to head gasket. Even at idle you should feel a slight puffing from the leak. Now you probably will not be able to get your hands everywhere so this is where your rubber hose comes into play. Do not stick the rubber hose in your ear or up your nose(welcome back cotter) but close. You should hear the sound when the rubber hose encounters the leak. The leak can be quite small so make sure you go all the way around the joints. If no leaks are found there, check further down the exhaust pipe.
From the video, it does not sound like a rod knock(actual rpm) as opposed to valve related(1/2 rpm). Yes exhaust leaks are 1/2 rpm.
Good luck
Mike