Originally posted by bnoon:
The other things I listed above need to be added to your knowledge. Low RPM's the pressure is lower, you're correct. That's why my oil light didn't come on though, I had good pressure. High RPM, pressure is high, also true, but pressure has nothing to do with the crank getting oil. Pressure has to do with getting oil to the top of the engine, not the crank. When the crank spins at high RPM, the oil begins to wrap itself around the crank in such a way that the air actually forms a barrier around the crank starving it from oil. It also actually makes the level of oil in the center of the pan dip down so the crank isn't getting the splash it's supposed to. This is called cavitation (SP?).
iirc, cavitation is something that happens when pressure falls below the vapor point, bubbles are formed in the liquid, the bubbles are then carried to areas of high pressure where they are released causing a wave in pressure...
The knife edge idea is an old one and works very simple. Sharpen the edge of the crank so that there's less surface area to carry oil around the crank and leaving the oil where it's supposed to be, in the pan so that the pump can pick it up.
The other way to cure this wrap up is a crank scraper. A simple piece of metal about an 1/8" away from touching the crank as it passes past the edge of the block on it's upward side. This scrapes the oil trying to follow the crank and forces it back into the pan where it can do it's work.
The second theory of mine is starvation which can happen two ways. One, buy the crank spinning so fast the oil becomes frothy with air bubbles. The oil pump sucks air bubbles along with the oil, not getting the full amount of oil to the heads because of the bubbles of air, therefore meening not enough drain back to the crank... boom.
I guess I would have to study the direction and path of the oil to better understand that one. If the Pump is pickin up bubbles from the crank case then wouldn't the crank case be the last place to receive the bubbles, meaning wouldn't other parts (like the cams) be starved before the crank?
The other way starvation can happen is that the oil pump is working so well that it sucks the pan almost dry and the gravity feed return holes don't flow well enough to get it back to the pan in time to be repumped back around.
A windage tray is made from either mesh or partly soild sheet metal directly under the crank to keep the oil off of the crank durring high RPM splash.
In all of these conditions, the external oil pump/resivoir (SP?) would work wonders by keeping a constant return supply to all parts of the crank.
Does that help any?
one more thing, if the crank is causing a barrier of air around itself how would increased oil in the crank case help this problem any?
