12

   We where having serious oil problems the last few times
   Dan flew it. The last flight we lost a full gallon and a half over board.
   Despite that it took only 1 minute 47 seconds to get to 10k
   and best the record.

   The oil pressure started at about 120 psi and by the time Dan
   got to 10,000 feet it was down to 50 psi. As soon as he leveled
   off it rose back to 120 psi. I suspected pump caviatation as
   the intake was about 3 feet below the oil pressure pump
   when the airplane had a 45 degree nose pitch up angle.

   The two problems were not necessarily related.

   One of the fittings on the tank, being used for the vent line,
   had damaged threads. Somebody cut the vent hose fitting nut
   down to compensate. That was a new trick on me. No matter
   your age and experience there is always something  new to learn :-)

   It worked as long as it was tight but it did not take much to
   loosen it. I believe thats how we got a half gallon of oil in
   the bottom of the fuselage :-)

   It just so happened I had a steel -12 AN fitting so I screwed
   that on and it cleaned up the aluminum threads.

   It is 1" & 5/16" by 12 threads per inch which just so happens to
   be the same size nut that holds the wheels on a tractor trailer truck :-)

   You can get steel dies in that size but  they cost over $50.

   Paul Lamar

If the engine was built with any end clearance on the side seals, I bet you are now seeing the seals wear in a bit and it is beginning to get a bit of blow-by of combustion gasses.A bigger problem in boosted engines.
I start new engines with less than zero clearance. So long as the side seal and corner seals return to height when released, that is the correct clearance.

There is quite a bit too much oil in the tank. Oil level too high. (my opinion) Scavenge oil packed with combustion gasses are returning to the tank at high velocity. This produces a fog of oil and air above the oil level in the tank. So, increase the diameter of the tube bringing in the scavenge oil and also the hose diameter at least close to the tank. 2" would be good. Larger would be better.

Actual fittings are of no value at all. Just a pipe with a rolled lip is fine. Flows great and weighs less.

The venting tube has the same problem and more. All of the gasses returning must enter that sharp edged tube in order to escape. So, because of the sharp edge the hose flows about one third of the rated diameter of the hose it is connected to. It also cannot be located anywhere near the scavenge return piping. And it is.

I would extend the threaded filler neck up and forward as far as is possible.Then, Just below the threaded neck add a 2 1/2" OD tube for breathing. A nice flair on the end of that tube right where it connects to the filler neck in order to assist flow would be nice. Run thin wall 2 1/2" tube out the bottom of the plane.

The suction side piping needs to be at least 2" ID. Again, no fittings just pipe with a flair. Rigid tube up to the pump then blue silicone hose to a tube welded over the outside of the pump inlet fitting. Work on the inlet end of that fitting to make it flow like the wind.

Poorly vented combustion gasses reduce oil pressure pound for pound. Poorly vented combustion gasses cost HP and can turn a main seal inside out. Or, push the seal out of the block. Don't make me come out there........

Lynn E. Hanover


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