I have a 91 Z28 5-Speed the previous owner had a 350 put in it. The dip stick has a crack at the top so I put a different on in, but when I was seeing if the old one would work at speeds over forty oil would spurt out of the top. What could cause this problem? Is there an engine compression problem? I also believe I have either a roller rocker tick or a lifter tick that I'm planning on fixing but don't want to if my engines compression is bad.

 

One possibility would be worn rings allowing combustion gasses (blowby) to build up pressure in the crankcase. You also need to check the PCV valve and make sure it's working, and that the vacuum source for the valve is connected and working. The PCV system removes the spent combustion gasses from the crankcase. But is can only handle so much.

Next would be a cylinder leakdown test.