Alittle more indepth here

Warm the piece that the screw is in NOT the screw up to 200-250 like nascardad said than use compressed air shooting threw a THIN tube at the screw it self

Why heat expands items cold contracts ....i do this to fix stuff thats rusted or stripped all the time

JUST be carefull NOT TO OVERHEAT the car or the mounts you can ruin them

Another way get some penetrating oil puts some dabs onto it leave it overnight to soak in try again in the morning (so you dont overheat yourself)


Dremel also works in some cases as well it just depends on the situation

is the bolt loose & stripped or tight & stripped ???

can you remount the other screws to the engine and try and back the stuck one out

just a few idea's good luck getting it out