[Fot] Fw: Help with Oil Pressure Problem

[Jack Wheeler]

I've never sent a message to the FOT group before, so I hope I am doing
this correctly.

I just finished rebuilding the engine in my TR-3, and it is
showing some unusual and disconcerting information on the oil pressure gauge. 
When cold, the pressure ranges from 60 psi at idle up to 80 psi at 3,000 plus
rpm.  However, last weekend, I took it out for a drive and after about 25
miles, when the oil was up to full temperature, the pressure dropped to almost
zero psi at idle, but still kept showing almost 80 psi at 3,000+ rpm.

I have
built these engines for over 40 years and have never had this problem before. 
The first thing I would think of is bearing clearance, and for years I always
checked the bearing clearances with plasti-gauge when I assembled one.  When I
was racing, I had a crank grinder who was so good, I gradually stopped doing
the plasti-gauge check (I never found one that was out of tolerance).  In this
case, the crank was standard size and the crank grinder recommended that he
polish it, which he did.  Although this guy is new to me, he was recommended
by someone who rebuilds race engines for a living, so I trusted him.  I guess
he could have polished too much off the bearing surfaces, although I would
have thought he would have checked that after he polished it (I certainly
should have - and will next time).  The other thing that could cause too much
bearing clearance would be bad bearings.  Has anyone seen problems with main
or rod bearings, resulting in excessive clearance?

The only other thing I
could think of is a failure of the pressure relief springs in the oil filter
head.  The long spring, which is used to adjust the pressure is still
available, and I
 always replace them when I rebuild an engine as standard
practice.  The shorter spring, which is there as a fail save to keep the
engine from starving for oil if the filter gets clogged up, is not available,
and I have never replaced one.  I did not use this spring in my race car, as I
had a custom made filter head which excluded this oil pathway, but I have
never had a problem, that I know of, with this spring in street car engines.
Has anyone seen symptoms like this before, with a newly rebuilt engine, or
have any suggestions what might be causing this?  Thanks for any ideas/help
you can give me.

Jack Wheeler