Oil Cooling

Dear Buglover,

Yes. The idea of using #4 as a restrictor to increase either flow or
pressure has merit. But I do NOT think the purpose was to improve
oiling of the main bearings. As you know, the main bearings are the
source of pressurized oil for the connecting rods, although not on a
full-time basis. The oil passageways in the rods and in the crank
only align every 180 degrees, indicating that these bearings do not
require a great deal of oil for proper lubrication. (Indeed, this is
generally true for all plain bearings

I think the purpose of the restrictor is to increase the flow of oil
through the oil COOLER. As partial support for this idea is when VW
began installing the #4 plug in this fashion, that is, the 1600 engine
was known to have problems keeping itself cool, especially in tropic
climates such as Brazil, whereas theres no history of lubrication
failures.

With the HVX mods the oil cooling system is modified in that ALL of
the oil flows throiugh a low-restriction oil cooler (ie, the Mesa-
type). In a vehicle, the flow to the oil cooler is governed by a
thermostatic valve which by-passes the oil cooler until the oil
temperature reaches approximately 180 degrees. In an airplane, the
temperature is controlled MANUALLY. The pilot opens or closes a set
of shutters which controls the flow of cooling air throuigh the oil
cooler. Using manual control is a bit old fashioned but it removes a
component from the system (ie, the thermostatically controlled valve)
and gives the pilot the ability to pre-configure the cooling system
prior to take-off (ie, OIL COOLER - OPEN ). With a big engine (and
at least a quart more oil) you've got a lot of waste heat to manage.
Prior to take-off you can get stuck behind some guy doing his nails
and it may be twenty minutes before you're cleared for take-off --
plenty of time for your Oil Temp to creep into the red. Your take-off
run will bring it down a tad but you're at full throttle and as soon
as you begin your climb-out your oil temp will start to rise, Since
the angle of the aircraft will reduce air-flow through the oil cooler,
you'll want to keep your climb-out rather flat.

Tif you're just doing Bumps & Grinds out of some cow pasture you'd
probably have the oil cooler in the circuit all the time. But if
you're actually going to FLY somewhere, configuring the engine for
optimum performance at your cruising speed & altitude is critical
since it effects how much fuel you'll burn... which dictates how far
you can fly. Once you are at your cruising altitude your oil temp
will tend to be too cold. So you partially close the shutters until
it's back in the green. Ditto for a long descent, during which the
engine will tend to cool off.

With vehicles you can't always count on the forward motion of the
vehicle to provide enough air-flow through the cooler. Installing an
auxiliary fan is the usual solution, although there are designs out
there which utilize part of the output from the engine's blower to
cool the oil. This is similar in concept to the stock configuration
but on a much larger scale. (See Jake Raby's web site).

-R.S.Hoover

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Bob, I am following your instructionsand learning much. I have a
question as the longer plug to the #4 bearing is supposed to be a flow
balancer/ restricter to the # 4 bearing so most of the oil goes to the
crank/cam bearings. This is according to a forem on the samba. It
appears to me that the idea has some merit. I have pulled the plug and
tapped it according to your and several others instructions. I have
done the HVX oiling mods, ( I am at the jugs now.) any thaughts to the
idea? PS thanks for the help. Hope you get
better.