Originally Posted by santaclara
...their is a spring around the screen that we used to stretch a little bit to boost the oil pressure.
The spring isn't at the oil screen, (oil screen is in the boock) it's under a cap on the oil pump that covers the oil pressure relief valve.
The increased spring pressure raises the amount of oil pressure needed to lift the slide and allow oil to the bottom end. This results in increase oil pressure to the top end at idle.
What it does is forces all the oil to the lifters and the top end.
When the amount of oil directed to the lifters cannot pass through the lifters and the top end, it builds up pressure and raises the slide allowing oil to flow to the connecting rod bearings.
In a hot motor at idle, the oil flows through the top end and doesn't build enough pressure to lift the slide, thus depriving your bottom end from receiving oil.
The stock spring was designed to balance the needs of the top and bottom end oiling requirements. In the good ole' days, people would remove the stock spring and stretch it. Then your guess was as good as anyones as to when it opened.
The spring is used to compensate for other problems. As mentioned above, rocker arm bushings, lifters, pump body scoring, worn pump gears and lifter blocks are more than likely the cause.
I don't recommend simply stretching the spring.............