Tap it from side to side, and/or pry it front to back. DO NOT try to drive a chisel or something similar between the cap and the block. It's a precision machined fit, but it's not impossible to get the cap moving. The lower part of the timing cover gasket is probably holding, and don't be surprised if it tears. It's easy to fabricate a replacement from gasket paper.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!