[DeTomaso] head drilling for air release

[Tony DiGiovanna]

Asa,
Here's some more crazy things to check (been to all of them):
Is the thermostat right-side up?
Is the thermostat opening?  I usually run without one anyway.  That's not a
bad place to start.
Is there an un-supported length of hose on the inlet side of the water pump
that is sucking closed?
I once had a hose where the inner half separated from the outer half and the
inner half collapsed shut even though there was one of those helical spring
supports in it.  It looked and felt fine from the outside (cost me an engine
it did.)
You gotta watch new water pumps: There's a crapload of  potential mfg errors
that can affect you, e.g. impellers designed for the opposite rotation.  I
once bought two waterpumps of the same mfr and PN.  The impeller design was
a bit different between them, enough so that one overheated at idle and the
other did not.
Try disconnecting the water pipes at the front of the cockpit and use a
garden hose to flow water backwards thru the radiator.  Sometimes you can
expel crap that gets caught in the tube entrances.  Once, at a track event,
I reversed the lines to reverse the flow in the radiator.  Overheating went
away.  I didn't even miss a session.

Not sure why, but when I fill my coolant system, I always have some air that
bleeds out of the petcocks in the back of my heads.  Not sure if it really
is an issue, but it is there.