Here's a close-up of a Hi-Po main journal. Make your Hi-Po more reliable by giving main and rod journals closer scrutiny. Because journal temperatures can reach upwards of an oil-cooking 350 degrees F at high rpm, oil distribution is crucial. Oil passages must be clean and openings chamfered to improve flow. It isn't just about pressure, but also flow. This means bearing clearances must be spot on for the right balance of flow and pressure. Hi-Po main bearing clearances should be .0005 to .0028 inch. Ideally, you will have clearances in the middle of these two numbers.