It came with a purple spring in it and it feels a little bit stiffer than my white GM spring. I'm not sure what one to use.

 

man I would call melling and ask them about that. They might even have another spring to use.

 

Your pump is std volume std pressure with 3/4" inlet.
If I remember correct, pink is melling's high pressure spring.
Use the GM white spring if you want the higher oil pressure.

 

so they both do the same thing? Does one have more pressure than the other?

 

Did you buy the pump new? In my Melling select box the instructions in the box said what spring did what. I think mine had a white spring in the pump and a purple in the box.


David

 

They both give you between about 60-70 running psi at cruising speed and about 50psi at idle.
With the current spring in the pump It would be about 30-40 psi idle and 40-50 psi cruising.
My select pump only came with 1 spring and hardend shaft.

 

It's not very scientific but I put both springs on a screw driver with washers sepearting them, and the white spring was always taller than the one from melling, so the white spring is stiffer and will have higher oil pressure.

 

Yes