While we are on the subject of oil system mods this trick is
supposed to reduce the oil temp by 10 or 20 degrees F.
A pipe tap is shown but again the meat available is marginal so
probably best to use a face seal fitting with an O ring.
Paul Lamar
I am thinking of making this mode to my engine so I picked up a couple
of 9/16th straight thread face sealed to AN dash 8's. Dash 10 has been
traditionally used to plumb the oil cooler but it is a bit large
compared to most
of the oil galleries in the engine. Most oil galleries are 10 mm or
about
.4 inches ID. All the oil that goes into the engine passes through the
oil filter
mounting with a ten mm drilling. All the oil that comes out of the oil
pump
also comes out of a 10 mm drilling in the front cover.
Makes you kind of wonder why every body uses dash 10 for the oil cooler
plumbing
when that has .5 inches or 12 mm ID. The cast iron meat around this hole
with the pipe
tap sticking out of it is only about .85 inches in diameter. A dash 10
fitting with
straight threads (not pipe threads) would be around .7 inches in
diameter. That
would be pushing it and begging for problems. The pipe tap would really
be asking for problems as it would be easy to crack the front end
housing
by over torqueing the pipe threaded fitting.
So I decided to go to a dash eight size with an ID of 10 mm or about .4
inches.
Same as all the oil gallery drillings in the engine. It has a 9/16th or
.562 straight
threaded portion. That will leave about .15 inches of cast iron all
around
the hole.
Another advantage of this mod is there is an O-ring between the front
cover
and the front end housing that historically has given a lot of problems.
This passage and its O ring is eliminated by this mod.
I am still not sure why this mod would drop the oil temp. If it really
does.
BTW I found a place in Long Beach CA that carries a lot of these weird
fittings. Metric to AN for example. They also carry a full line of AN
bolts
and other AN hardware.
Deering Industries
330 Cherry Ave
Long Beach CA
90807
562 595 1668
562 595 1669
Not far from Mazdatrix
Paul Lamar
------------------------------------------------------------------------
Hi Paul,
Thanks for the analysis on the oil gallery size. Wouldn't the larger
-10 hose have lower pressure loses than -8 hose? Is it enough to
matter? Are you keeping the oil pressure regulator that mounts to the
bottom of the front cover? If so, the front cover/front side housing
oring seal and passage has to remain so that the regulator can 'do it
thing' between the oil pump and the oil cooler. In this case the front
cover hose outlet hole has to be plugged as well.
Ken Powell
Yes but I am willing to bet it would only be a few psi.
Good point on the oil pressure regulator. Actually what it is
is a oil pressure limiter and it is set to 150 psi or so.
The real oil pressure regulator is mounted near the bottom
of the rear end housing and is set to 80 psi or there abouts.
If you always use 15W 50 multi viscosity oil and never try to
start your engine after it sits outside in below zero (F not C)
weather it should be unnecessary in an aircraft engine.
For one thing we don't zing the engine. The prop load will see to
that. If you zing a cold engine with thick oil without the oil
pressure limiter you could shear the oil pump shaft.
Paul Lamar
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