Oil Pump relief spring confusion

[Lynn]

I posted a while back about wanting to DECREASE the oil pressure on my El Camino. Not unusual for it to go straight to 80 psi when cold, and it stays up over 60 psi just cruising, even after warmed up.

When I built the motor I bought a Melling high volume oil pump. I did not specify high pressure. Supposedly that pump comes with one spring installed and another to swap in if you DON'T want high pressure. I did not receive a second spring.

After multiple inquiries about the correct bypass spring, I really got frustrated (seems to happen more often the older I get) as all the talk on line deals with wire diameter, number of coils, free length; in other words everything EXCEPT a plain English explanation for pressure relief in psi!!!!

Ran across this chart:

Oil pump bypass springs.

----pump -----------wire dia.-----coils---------free length------oil pressure-----spring color
stock M55 SBC-----.037”-------23.0-----------2.235”-------------47psi-----------plain
stock Z-28 SBC-----.041”-------24-¾----------2.210”-------------NA-------------white large end
misc SBC-------------.037”-------24.0-----------2.220”-------------NA-------------plain
misc HP SBC--------.042”--------26-¾---------2.390”-------------NA-------------blue

stock 454 BBC------.040”-------26.0-----------2.580”-------------47psi-----------plain
stock 454 BBC------.041”-------26-¼------2.400”to 2.450“----52 to 65psi-------green
HP BBC--------------.040”-------21-¾----------2.460”--------------NA------------yellow
HP BBC--------------.042”-------26-¾----------2.650”--------------NA------------pink
HP BBC--------------.0415”------26-½----------2.550“-------------NA-------------blue
misc BBC-------------.039”-------26-¾----------2.530”--------------NA------------plain

Posted here: https://www.speed-talk.com/forum/viewtopic.php?t=28642

Clear as mud, right?

All well and good; but at what psi does each spring provide relief?

Finally found a common sense answer; at least if you are dealing with a Melling oil pump for a SBC.

Instead of paint color or lack thereof, you just need to order by part number. The psi for relief is simply the last two digits of the part number. Can't believe this wasn't easy to find.

55049 = 49 psi
55058 = 58 psi
55070 = 70 psi
55078 - 78 psi

Hell's Bells, even I might be able to remember that!

Supposedly, the springs interchange between the standard oil pump and the hv oil pump. I will know for sure this weekend. Finally pulled the motor on the El Camino to address this issue as well as some burned valves as a result of it overheating (due to the failure of a brand new thermostat that stuck shut).

[Too Many Projects]

Ha, those are all zip codes in MN. I lived in 55070 for a few years.