Why is too much negative crankcase pressure bad for rod bearings?
02-06-2006, 09:23 AM
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Why is too much negative crankcase pressure bad for rod bearings? I've read about using a vaccum pump to create higher than normal cranckcase vacuum to seal the rings better and give better performance. I've also read that too much can ruin your main bearings.
I'm assuming that the vacuum draws the oil out of the bearings before it can be replenished but I would think the the oil would see the difference and more would flow into the bearing because of the pressure differential. I.E. if I had 50psi at the pump and -8lbs. in the cranckcase, the oil would see a pressure differential of 58psi and that much pressure would be applied to the bearings.
I'm assuming that the vacuum draws the oil out of the bearings before it can be replenished but I would think the the oil would see the difference and more would flow into the bearing because of the pressure differential. I.E. if I had 50psi at the pump and -8lbs. in the cranckcase, the oil would see a pressure differential of 58psi and that much pressure would be applied to the bearings.
