Short answer, the #8 bolt is bigger than the M4 bolt, but will likely still fit in the M4 clearance hole.
#8 bolt: Major diameter: .1640"/4.1656mm Close fit: .1695"/4.3053mm Free fit: .1770"/4.4958mm
M4: Major diameter: 4mm/0.15748" Close fit: 4.20mm/0.165354" Free Fit: 4.40mm/0.173228
Some sources:
http://www.diyaudio.com/forums/parts/150402-8-32-bolt-fit-4-5mm-hole.html
English clearance holes:
http://littlemachineshop.com/reference/tapdrill.php
Metric clearance holes:
http://littlemachineshop.com/reference/TapDrillSizes.pdf
