Getting rid of crankcase moisture via vacuum.

[Gedon]

I have a pretty full on engine that I'd like the gears and bearings to last on. Rather than filling it up with MoS2, I'm seriously looking at running castor oil. The main snag the moisture from blow by causing the oil to form gums/acids. I have the engine in bits and am at the point where I have to choose castor or mineral....

The question is, does anyone have any experience of removing crankcase moisture in this manner, or the sort of pressures pulled?

I gather that the sort of pressure pulled is about 30in H2O, which isn't much at all. I think this would cause water to boil at about 98 deg C, which is still way over the engine temperature.

Anyone got any better figures or suggestions. (Please don't suggest synthetic, as the gears will tear themselves apart)

[Mr2Mike]

Ask in the classic Mini forum. There are quite a few guys that race/rally minis in there, and they all seem to rate Valvoline Racing 20W50. I think Castor oil just has too many negatives to be viable with such high spec mineral oils available now.

[GreenV8S]

I think you're talking about positive crankcase ventilation. Usually this runs at relatively low vacuum, apply too much and it can cause problems with seals around the crank case. Also of course when there's no vacuum (when you've got the throttle open) there's no positive ventilation so you are back to the old fashioned sort. With PCV you would usually provide a carefully sized crank case vent to let (filtered) fresh air in, so it's actually scavenging rather than just keeping the pressure down.

You can get PCV check valves to maintain the crank case vacuum, these are essentially a pressure regulator.

[HiRich]

My experience with Castrol R on a pre-war engine is that it will always wax up if left, and always requires priming. First run pre-season is a nervous time. Silkolene do some mineral oils at SAE40 and 50 - why not PM Opie?