i have just found that i have zero compression on my number four cylinder. its a bored and stroked 454. what are some of the possiblitys that it could be? vavles? piston? what would likely cause it to have no compression at all?

pull the head...only way to be sure...

Do a leakdown test on that cylinder ,good luck

See if you forgot to put the spark plug in. Just kidding. As RHR stated, do a leak down test and listen to where the air escapes from: intake, exhaust or (hopefully not) the block.

loosen rockers and check compression again..