Tachs and Oil pressure

["Brad Meilink" <bmeilink@domain.elided>]

Two questions.  The first has to do with the oil pressure on my 87 Spider.
(54500 miles)  The oil gage goes to well over half when car is first started
in the morning.   After running and engine temp is at about 175 to 190, the
oil pressure falls off steadily to about 1/3+ when running.  I think that
this is how it should be, maybe a little low.  What worries me is that when
the engine and oil is hot, particularly on one of these 100F days, the oil
pressure falls to VERY near 0 at idle.

The car has a new oil pump in it.  Oil level is topped off.  Is this normal?

 I'm going to change the oil Saturday and put in Mobil 1 15W/50 synthetic
juice.  I hope that this improves the situation.  Please comment on what I
should be expecting regarding oil pressure, at speed, at idle, when HOT!.

My second question has to do with my tach. After watching it over the last
couple of days, I'm sure it isn't operating right.( It hung at 1000 RPM at
70 mph)  It never reads over 3000 RPM, even at 80+  MPH.  Typical is 2400
RPM at 70 MPH in 5th gear.  As I understand it, the tach on this vehicle is
electronic.  Is there a ground that I need to clean up that will make
everything right with my tach?  Has the whole thing gone to hell?   Godfrey
suggested testing and calibration in Palo Alto, CA.  I'm on the other coast
and will probably leave it alone if I can't fix it myself.

Any insights, suggestions, and repair tips will be much appreciated.  I've
owned this car (1st Alfa) for about 6 weeks, replaced the u-joints, rear
brakes and rotors, master cylinder, flex joint, all fluids except engine oil
(PO Jiffy lube special prevented removal of drain plug, will do Sat.),
supplied all my own labor and your input where needed.  LOVE THIS CAR!!

Thanks for your continued support of my latest vice.

Brad
87 Spider Quad
Harrisonburg, VA

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