plsirl

My 68 Mustang (with a 91 302) has started making a sharp "tap tap tap" noise. I am assuming this is valve tap, but others have told me that piston slap and even an exhaust leak can make a mechanical tapping like this.

Does anyone have links to these sorts of sounds on youtube or anything?

What's the quickest way to diagnose which valve is making this noise and which part of the assembly needs to be replaced?

Any and all related information is very well appreciated. Thanks!

Chopper

Noises are impossible to diagnose over the internet but here goes anyway.
A valve lifter that has collapsed or is in the process of collapsing will make a tapping noise that's one half of crank speed.That is,the sound will occur once for every two crankshaft revolutions.The noise will be a sharp metallic tap like a small hammer against a firm metal surface.
Piston slap will usually be worse when the engine is started cold and will eventually quiet down or go away completely when the engine warms up to operating temperature.This sound will be at crankshaft speed and will sound like the valve lifter only faster.
Exhaust leaks will also sound off at one half crank speed but will have a somewhat softer sound due to the fact that they are a result of gas escaping and not metal against metal.An exhaust leak can be tracked down by looking for black soot deposits around joints in the piping.You can spray large amounts of carb cleaner into the intakeand look for traces of escaping smoke.

Here's a link to a site that might be of some help.
http://www.bullittarchive.com/7000.htm

Go to the "noises" link and have a read.