One issue I found after installing a stronger pump spring was that the fuel pressure was erratic because the pump could not fill fast enough. i opened up the check valve passage ways which helped a little, but I found that installing a large prefilter vertically so it had an air pocket in it solved the problem. The air in the filter would act as an elastic of sorts, allowing the fuel pump to draw in a charge quickly and then the lower pressure in the filter would draw fuel in slower, like a capacitor does for an electrical circuit.

When I put the engine in the 201 chassis, I used the electric fuel pump to supply the lift pump. I made a pressure regulator to control the pre lift pump pressure, that really made a difference on the top end fuel supply. The stronger pump spring makes the lift pump really want to pump a lot of fuel so I am able to maintain a high pressure with more return flow that OEM. I can see the pressure pulses being at a higher frequency if the return flow was restricted, (not allowing the piston to follow the cam and bouncing off the top of the lobe). I am running a higher volume bypass as well and my thinking is in order to have increased volume, the piston must be following the cam profile closer on the return side, so it could then be argued that the pump frequency should be lower that OEM.. All theory of course..

My goal was to increase fuel supply and pressure, pressure frequencies were not a consideration really, but worth keeping in mind should any strange performance be experienced..