I would imagine the more oil is bypassed the hotter the spring gets. High pressure oil going through a passage heats up.

Everybody has been hammering you with this. A high volume pump is gonna tend to push more oil be the pressure relief valve. If I am right about the temperature reaching the spring. Then there you go.

I ran high volume pumps for years. Don't think you have a real issue. I would also think your Kevco Pan holds more than 5 quarts. I think you are probably pumping your pan low and loosing a little pressure.

Do you have the oil to the heads restricted at all? Depending on what rockers and cam you are running restricters may help. My engines ran grooved cam journals to oil the rockers all the time. Does your engine do this? If so there is a lot of oil going up top. Without restrictors you could theoretically be pumping your pan low.