New cam / timing question. Also hose sucked shut

I just spent the day yesterday installing a new XE268H Comp cam and lifters into my 73 Dart Sport 318. Ran out of daylight screwing with the oil pan to timing cover seal, but that's another story. Changed oil this morning and fired it up. I left the radiator cap off to bleed the air. Ran around 2000 rpm to break in the cam and let lifters spin. After a few minutes coolant was spewing from the radiator outlet almost like you see when you have a cracked head gasket. I put the cap on and the upper hose sucked completely shut. I shut her down, filled the coolant and capped it off. When I started it back up the hose started to collapse - about halfway - then it was like I could almost see the t-stat open and it filled out to normal. It has been fine since. After 20 minutes of 2000 rpm it never got over 210 degrees. I think it was air locked. Anyone got any ideas?

Also, with the new cam, do I use factory timing specs or do I modify them? It runs very well where I have it, but I like to do things properly.