Dropping Engine Temperature 20 Degrees

Starting the Packard Straight 8 last month really got us excited about getting the old coupe going again.  With many phases of the restoration still left to complete, we decided to finish the few things on the engine and run it through its tests, completing the drive train.  Our digital thermometer tests last time gave us uncomfortably high block and head readings (see temperature chart below).  Our radiator had already been rodded out, and top and bottom tanks reconditioned.  The head gasket was not blown, nor were the block or head cracked.  We had been waiting to remove the freeze plugs until we made a before and after comparison, and what a comparison it turned out to be!  First, we drained the coolant from the system and removed the water pump and thermostat housing, as well as the drain plug on the low end of the block.  Each of the five freeze plugs were tapped out using a blunt chisel on the bottom corner and pulled out with channel locks.  On Packard 356 engines, they are easy to get to.  The starter must be removed and the distributor wrapped in plastic (all freeze plugs are on the driver's side).  With the freeze plugs out, we  put our fingers inside one of the holes and were able to scoop out years of rusty scale that was not going to come out any other way.  Using a garden hose, we washed out each hole until the water ran clear, then used a small magnet and pick to dig out any remaining debris, after which we flushed once more with the hose.  With the thermostat housing removed, we flushed with the hose aimed down through the head.  More rusty silt washed out.  Eighteen years of sitting sure can build up a lot of rust.  We continued flushing until the water ran clear, then we put everything back together.  It is important to blow out with air any remaining water from the bolt holes.  Water and oil don't compress, and tightening down a bolt in a hole full of water could crack the casing.
        The freeze plugs were Dorman P-41C, but Dorman has changed their numbering system and now uses 555- as a prefix for its new freeze plug numbers, ours being 555-041.  As an extra precaution, we measured with our calipers and agreed the size was 1 61/64", a deep cup plug.  To install, we cleaned out each freeze plug hole with a wire wheel on a die grinder, then wiped around the hole's edge with Permatex 2-B.  We then knocked the plug in straight, using a freeze plug tool.  There are three types of freeze plugs:  brass, bronze and steel, brass and steel being the most commonly used.  The basic difference is that brass doesn't rust and won't pop out during extreme cold weather, because the metal stretches.  Steel will rust, but will usually pop out in extreme cold (which they're intended to do), allowing room for expansion, should the coolant start to freeze.  We chose steel for our engine because if the cooling system is properly cared for, rust isn't a factor, and we wanted the engine protection.  
        Another concern was the oil pickup tube.  We had previously had the valve covers off, cleaned that area, and had changed the oil twice using 30 weight oil and Marvel Mystery oil flush.  Although the oil looked clear and pressure was good, a hydraulic lifter would occasionally start clicking, and the fact that the car had been in longtime storage told us the oil pan had to come off.  We jacked up the car, drained the oil and removed the oil pan bolts.  On the straight 8, the front of the engine must be jacked up about 1-2" and the front motor mounts unbolted.  We slipped a piece of 2x4 under the motor mounts to keep the engine up so we could remove the floor jack.  We removed the cast iron bell housing inspection cover, removed the exhaust pipe bracket, and lowered the oil pan.  Before it would come off, we had to unbolt the pickup tube.  As we reached our hand in to do so, we could tell that the bolts were loose (not a good sign).  Eventually this tube would have worked loose enough to suck air and some serious damage could have been done to the engine.  The pan went to the parts washer.  There was about  " of sludge in it.  This was thoroughly washed out with mineral spirits, then the outside was washed with Acryliclean and painted Packard Green.  Cleaning of the pickup tube was more critical.  The screen was about 40-50% blocked.  A new pickup tube was not readily available,  so Joe used a screw driver and extreme care to un-crimp and remove the screen.  The pickup screen and mount was soaked overnight in carburetor cleaner, then cleaned by hand with a brass brush to remove all varnish.  The carburetor cleaner was washed off with water, then all parts were cleaned off with mineral spirits and blown dry (It is crucial to remove all carburetor cleaner from the pickup tube.  Just a trace will contaminate the oil and cause damage).  The screen was carefully re-crimped and assembled.  The oil pickup tube to mounting bracket was a machine fit and did not require an O ring, although a thin paper gasket was cut to go between the bracket and the block.  All of the bolts were cleaned and painted and a new pan gasket was installed,  putting Permatex 2-B on the pan side only, and a thin film of oil on the block side of the gasket, which would permit a non-stick release to the block side if the pan had to come back off at a later date.  We now put everything back together in reverse of the above, using a 1/4" drive socket set to tighten the pan bolts.  Over-tightening them with an air wrench stretches the pan and causes oil leaks.
        With the block cleaned out, now the question of what kind of oil to use:  detergent or non-detergent.  In most of the other old cars, we have stayed with the OEM non-detergent 30-weight oil, the exception being our other '48 356, which was switched to detergent 10W30 when it was cleaned out six years ago, and has had no problems since.  With that in mind, we put 10W30 in this engine as well.  So, now that the engine was clean, the next step was to start it up.  First, we removed an auxiliary plug from the oil gallery and connected a manual oil pressure gauge, then started the engine.  Upon starting, the oil pressure was 50 lbs at cold idle.  At running temperature it dropped to 40 lbs, compared to around 30 lbs before cleaning the pickup tube.  At running speed, the oil pressure increased from 42 lbs to 58 lbs.  This was much better than we had expected!  The operation of the cooling system has a direct effect on the viscosity of the oil, which affects the oil pressure.  When a car has sat for a long period of time, it is always best to clean out both systems.  Keep 'em driving!