JG,
I doubt that it would..... but maybe if the bubble were to find it's way to a mechanical gauge??? Don't know. Don't think so though.
I DO think that Dave has the right idea......
Talk to an engine builder. I agree that it should not matter..... But apparently something is happening!
RB,
No. Shimming the the spring makes it stiffer. Not "tricking" the system. Just changes the dynamic of the spring that controls the pressure.
Steve
PS,
Sorry! Trying to catch up on emails and threads. I'll do some research, and see what I can give eveyone.