4-5 minutes sounds like way to long to run an engine without water but, how many cars ant trucks have overheated bad while driving them before the driver noticed they were hot, then refilled and end up fine.
I have not been following this thread very close but it sounds like the head gasket was damaged before or during installation.
There was a question asked earlier about a leaking Clifford intake manifold, which could cause this problem, but the only response was that there was no water to the "exhaust" manifolds on this job.
This may have been a misprint. I would like a confirmation that the intake does not have water flowing through it for heat. Clifford manifolds are known to leak internally.
