What causes this, the motor has about 600 hrs on it with a top end refresh at about 350 hrs, motor was up to operating temps and a couple quick runs at around 4800 revs this happened, I looked for another thread on this but no hits.

thanks

May need a little more info
B U T
Sounds like & or could be blow by
Good place to start is a compression check

that happened to me because the motor had leaned out due to the carb loose and allowing unmetered air in burning a hole in one of the pistons witch allowed compression into the engine blowing the oil out the dip stick

Check your pvc system as well. If its clogged you will get this.

Do the compression & leak down checks too.

Its caused by too much crank case pressure. Check/replace your PCV first.
Simply, too much air is getting into the crankcase and can't get out so it forces the dipstick out.
It could be caused by bad piston rings.

Time for a leakdown test- Smitty

Agree with leak down test. Sounds like blow by. Maybe rings?

I'd start with crank case venting and then go to leak down test if that's not it. FWIW I have a 454 mag mpi with 1085hrs that's never been opened and still has great compression and no blow-by problems, so it's probably not down to "normal" wear and tear.

Take your oil fill caps off on a warmed up engine at idle to maybe 3500 rpm with some mild reving and see how much smoke is coming out of the holes.
It should be little to none. If you have smoke coming out, then its blow by. Take note if one side is significantly worse.