[SINISTER]

I'm guessing the motor is installed in car?
Since the bolt is soft,hit it with a sharp punch.
Start with small bits and lubricate with PB blaster.
Work your way up with larger bits until most of the bolt is gone.
Drilling straight is very important.
Once most of the bolt is gone,the thread portion should remove easily.

 

[SINISTER]

Grade 8 bolts can tear up the threads in the block if they are rusted badly.
Easier to remove a soft bolt than repairing threads...but they both suck.
I save every nut,bolt and washers from my tear downs for this purpose.
You can usually tell when a bolt is getting weak...but not always.

 

[SINISTER]

Bits are easier to remove than en easy out..as they usually break at the drill.
Easy out usually break off at the bolt.
All bolts should have markings on the head to indicate strength.
I Save everything from all my projects into jars for later use...comes in quite handy.
Buying cheap bolts at an expensive price from the local hardware store really sucks.