For the most part, I think that the hose would rupture and leak before it would actually blow off of the pipe on the pump if somehow there were excessive pressures. It must be something else.
Do you have the production return pipe at the valve? Is it oriented so that the short straight length angles slightly forward when the pipe is tightened on the valve? Are you using the right length rubber hose? It should be roughly 14.5 inches long. Are you using the production pump reservoir? The return hose tube on the reservoir should be pointing down.
If you have an AIM book it has a description (not really clear however) of the hose routing and how the pipe(s) are to be angled on the valve. If you need one, I can scan it and have Terry Rudy post it at http://www.corvettefaq.com
in the Steering section.
[Modified by Jim Shea, 11:41 AM 10/20/2003]