[Staowners] Oil Issues at High Revs

[Rowan Charrington]

Greetings All,
Just thought I would pass on my experience with my 1955 MKIII Sunbeam Saloon regarding the emptying of it's sump oil when held at sustained high revolutions.

I have only used GTXII oil (20-50 grade) in all of my vehicles since it came on the market and continue to do so with the Talbot, even though the specified oil is SAE30.  All my engines have been long lived and I am convinced that GTXII was, infact, created on the 8th day by you know who.
On a recent drive with our club from Darwin to Katherine (Northern Territory, Australia) I had the opportunity to stretch the old girl out on our then unlimited speed Stuart Highway.  Most of the 300 km drive was at 90-100km/h with no problems.  However, when I took her up to 120-130 km/h for about 15 kilometres, the oil pressure suddenly dropped away (from its normal 50 PSI+) and the temperature rose rapidly.
On stopping I found oil all over the left hand side of the engine compatment and engine and the dip-stick dry.  Radiator was full and no sign of any reason for so much oil to have been lost.   After topping up the sump with approx 3.5 litres, the motor started OK with no noise and normal oil pressure and water temp again.  No sign of any oil leaking from anywhere on the engine.  Drove on to Katherine at 90-100 km/h without further problems and also on the return the following day.
I checked out compression (better than specified accross all cylinders), no sign of oily plugs or exhaust smoke, everything as good as could be.

The only logical reason for the loss of oil is that the GTXII at its 50 grade viscosity is slower in returning from the side cover cavity to the sump through the standard cast drain holes in the block.  This would be exacebated by the higher revs in the standard top gear (NO overdrive is fitted to my MKIII) causing the 50 grade oil at 50 PSI+ to exceed the drainage capacity of the side cover cavity until it backed up to the breather pipe level and then to flow, be blown or sucked out the pipe and all over the engine compartment.   This problem would obviously be mitigated by, 1) lower revs used when overdrive fitted, not driving at sustained high speeds with a 50 grade oil in normal top gear, going back to 30 grade oil (not for this Kid).  I have noticed that some earlier Talbots had side cover breather pipes that were curved upwards before dropping down to the sump level filter outlet so maybe this was an issue even with the 30 grade oils.
Anyway, just some food for thought.
Regards,
Rowan Charrington
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