Originally Posted by 68NovaSS
If you don't want to take the thermostat housing off to drill it, you may get by with burping it, purge air. With the cap off rev the engine some, you'll see water moving through, that'll push air out. Add coolant as you go, cap it as soon as you've done that a few times.
It's old school, but it's worked for me.
X2 This is how i always do it also and it has always worked for me too.
The pics above are to show you what the others are talking about.