petcock valve at the rear of the intake manifold.

["Arthur Siemens III" <asiemens3@cox.net>]

Hello,

I'm new to posting messages here but have been reading various other
postings for some time now.  I have a 67 roadster that seems to be always
boiling over.  I have yet to look into it with a greater amount of detail
and I have read a lot of suggestions on how to go about diagnosing the
problem.

My question is what is the three way valve found at the rear of the intake
manifold used for.  I know that it is part of the cooling system, but which
way should it be turned to?

Arthur