Who wants to play "guess why this cylinder has no compression?"

[bryantreams]

Alright folks, bit of a sad day for me. Pulled out of a parking lot somewhat quick and a new noise came from my engine compartment. Sounded like an exhaust leak. Limped her home where I was already planning on swapping spark plugs and doing a compression test while I was at it. Here are the results
Cylinder-psi
1-135
2-145
3-135
4-0 (zero)
5-135
6-115
7-135
8-120


Cylinder 4 spark plug was oil fouled but not physically damaged.
Waiting to do a leakdown test tomorrow so I thought I'd post this to see if anyone cared to guess what's up with it. At this point I'm bummed out a little but have already started searching for a 454 to throw in her.