Oil pump piston, some questions.

[The Radium King]

it's a pressure valve. if oil pressure exceeds a certain value (as determined by the spring) then oil pump will bypass back to sump.

you will see high pressure at start-up with cold oil. the stronger spring keeps the oil circulating a bit more before bypass which will help lubricate the chains.

also, the oil pump pressure is dependent on rpm - pump spins faster as rpms increases which results in increased oil pressure. so when flogging it around the track at high rpm expect that some oil gets bypassed to keep pressures within spec. something to consider when trying to determine where to plumb-in an external oil cooler or accusump.

also, when oil starts to build up in the heads when doing higher-g turns, pressures will increase and your pump will start to bypass just when you need it the most.

so, stronger spring is good.