Get a long drill bit, and a variable-speed drill motor, and ream those holes out. Then use a can of Wynn's "Engine Cleaner" in the oil, and run it for 30 minutes or more at a fast idle. Drain it while it's hot, and change the oil and filter. You'll need to install new valve guide seals to minimize the oil consumption.
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!