8ba oil pump

[52merc]

i have seen posts on here a while ago about either stretching the spring or putting a couple of small washers behind the spring to give more tension what exactly does this do

[feelsharp]

It increases the pressure output. My attempts have been trial and error--try a spring and see what that produces, try another until the pressure is where I want it. Mine have all been the other way, to decrease pump pressure when installing new pumps on old splash system engines.

[52merc]

btt

[JWL]

Shimming the spring can raise the POTENTIAL oil pressure. In other words, the pressure at which the bypass valve opens to re-route the oil within the pump. However, the actual pressure seen on the gauge, attached to the engine, might not change at all except when the oil is cold. The volume of oil output by the pump must meet with adequate flow restrictions, which are primarily controlled by bearing clearances and leakage at the pump housing, before the pressure can build to the point of the bypass valve opening. In many examples the hot oil rate of flow goes beyond the pumps ability to reach the volume required to reach the valve opening settings. Most 8BA pumps have a bypass setting of around 50-55 lbs. I consider that to be completely adequate for most engines.

[52merc]

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thanks jwl