Found this. Interesting read.
http://www.precisionenginetech.com/tech-explained/2009/06/01/race-bearing-tech-part-2/
So far in reading I have found a couple points to consider for cavitation. Run less bearing tollerance and lighter synthetic oils with really high fluid film strength to reduce the likelyhood of cavitation, that is clasic cavitation like the expansion and collapse of bubbles.
Running too too thick of an oil viscosity wise, can reduce oil returning to the pan and increases foaming and allows the oil pick up to introduce air into the system (some folks call the air introduced cavitaion). Even small amounts would be nasty and degrade the film strength over the bearing. It also generates more heat which can predispose the bearing to clasic cavitation.
Here is a quote from an article. Link is below it.
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If the oil selected is too low in viscosity, heat will generate due to an insufficient film thickness and some metal-to-metal contact will occur. If the oil is too high in viscosity, heat will again be generated, but due to the internal fluid friction created within the oil. Selecting an oil which is too high in viscosity can also increase the likelihood of cavitation. The high- and low-pressure zones, which are created within the oil on each side of the area of minimum film thickness, can cause oil cavitation in these bearings. Cavitation is a result of expansion of dissolved air or a vapor (water or fuel) in the low-pressure zone of the bearing. The resulting bubble implodes, causing damage, as it passes through the high-pressure portion of the bearing. If the implosion or collapse of the vapor bubble occurs next to the metal surface, this can cause cavitation pitting damage to the metal. If the implosion of the bubble occurs within the oil, a micro hot spot or micro-dieseling can occur, which may lead to varnishing within the system."
http://www.machinerylubrication.com/Read/779/journal-bearing-lubrication
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It seems that fuel and water contamination of the oil are the two main culprits ive found for cavitation to originate from. I would think that a good bypass filter can easily remove the water, but the fuel is much harder to get.
It might be worth a shot to get a nice bypass filter set up and perhaps run a good synthetic like rotella's 0-40 for example. I would say amsoil or redline as well. Amsoil has a lot of grades to choose from. Id say almost anything would be a step up. That is not to slam you, its just those bearings have seen some hard times and you were treating them pretty darn good with your oil quality and frequent changes.
I would think a synthetic will shed faster returning to the pan and they also foam less. I dont know about running tighter bearings but some builders only go 5 thou tighter. You can gain a couple thou with moly coatings right there. A bypass filter with an element to catch water is easly to install and maintain. lastly id add zink and moly additives for a final critical wear barrier if (when) the film degrades and you get metal contact. Most modern oils have had their zink content reduced quite a bit.
Thoughts?
g
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