Brian - bcrulifs@eos.ncsu.edu
asks the following:
> Subject: Oil pressure drops on turns
>
> I've noticed this phenominon with my 73 MGB recently where on hard
> corners the oil pressure will drop to about 20psi and stay there for
> about 5 seconds. The oil pan has the full amount of oil (it happens
> with oil levels anywhere from max to min on the dipstick).
> It's quite annoying to be throwing her through some corners, and just
> as we're about to accellerate off again, I look down and see the oil
> pressure gauge reading 20! (It stays at about 70 during normal times).
> Can anyone explain or diagnose what's wrong? Thanks in advance.
I used to race an MGB in SCCA E production.
What you describe is fairly common
in cars that have had tires and suspensions
modified so they can corner at "G-forces"
higher than originally intended by the
engine designers.
What happens is centrifugal force causes the oil
to flow to the outside of the oil pan.
In extreme cases the oil pump pick-up is
no longer fully covered with oil and oil
pressure drops. The Bently reprint of the
factory repair manuals includes a section
on competition modifications. This includes
modifications to the oil pan to reduce
this situation. The factory would not
publish this if it did not happen
to modified MGBs with stock oil pans.
In addition to the recommended modification
of lowering the deep portion of the pan by about
1 inch, the pan I used had additional baffles
to try to keep the oil around the pick-up.
Some cars designed for racing use a
"dry sump" oil system.
Due to expense and complexity,
very few MGBs used full dry sump setups.
However, there was a device called "ACCUSUMP".
This was a device, called a "pressure accumulator"
in aircraft, that held 3 quarts of oil under full pressure
and would maintain the oil flow to the
bearings when the oil pump could not
pick up oil from the sump.
I do not know if this device is still available.
Five seconds is a long time to run an engine on
full power with reduced oil flow (the low pressure
is a sign of low flow in this case).
My experience has been that
each corner taken under these conditions will
eat into the lifetime of your rod bearings.
Gary Smith
64 Austin Healey BJ8 (Phase 1) - Might run again next year
66 Austin Healey BJ8 (Phase 2) - Completely disassembled
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