I just recieved my new Melling Select oil pump with the pink spring installed. Should I remove this spring and install a slightly lower pressure spring? How much is too much oil pressure? The reason I am replacing my pump is my pickup fell off and word is that the regular m155 had a weak casting. Right now I get 20 psi at idle, 45-50 psi at WOT and approximately 60 psi at cold start. What will I get with the pink spring? Is it true that the pink spring is similar to the white spring that gm uses?

 

I went with the white spring as I wanted higher pressure...I get about 100psi on the gauge on cold start and about 35-40 psig at warm idle. I'm not sure what it yields at WOT since I'm usually looking outside at that point...lol

You may get a ton of posts on my next comment. I don't really think there is a too high a pressure. My thinking is that the crank and cam are floating on a high pressure cushion of oil so higher oil pressure should give a higher degree of safety. I think the pump does work harder to generate this higher pressure as the spring opens a relief port to bleed off pressure, lessening demand. So that's a power loss b ut I haven't a clue how much.

I'd leave it in there.....if it is essentially the same as the white spring.

 

The Melling pink spring is supposed to be a 70# spring which is essentially what the GM white spring is supposed to be.

 

Use the high pressure spring.

 

Guess I'll be the first. Since you put it in BOLD lettering: "I don't really think there is a too high a pressure." I just couldn't resist, LOL.

Actually, you can have oil pressure so high that it'll overwhelm the oil filter gasket and you'll end up with your oil all over the ground. Been there - back in the day when shimming the bypass spring was all the rage.

I never had a filter burst on me but I know a guy who did. Gear wear is increased too.

One of the pump mods some resort to is to enlarge the bypass hole in the pump. Seems that even though the spring is depressed enough to allow oil to bypass, the hole isn't large enough to handle the extra flow.

Jake

 

I preceeded my comment with 'you'll get a ton of posts on this'...but I only got one.

You raise a good point about oil filters. We should always be using a high quality filter to minimize these types of faults. As a supplier to the industry through Honeywell, I'd stay a country mile away from Fram filters, simply due to the construction of the canister and the seals. Moroso filters, whomever makes them, seem to be of more than adequate strength.

I guess we have a difference of opinion on one of the other comments. I don't know about the potential for increased pump wear so I won't argue. However, the comment about the pump orifices not being able to handle the extra flow doesn't sound right to me. Increasing the pressure is acheived through a stiffer spring that doesn't uncover the port until it's resistance is overcome. There isn't any greater flow, it just happens at a dfferent 'time'. If we were talking about higher volume pumps, I would certainly agree....

 

i misunderstood what you posted, so you win at being the first.

Trying to recall now, but it was either in an engine build-up article or a mag advertisement about Mellikng or Moroso increasing the bypass size in one of their pumps. I didn't pay a whole lot of attention to it because it's something I've know about for years. So I didn't save it to my memory banks, LOL A Google search would probably turn up more info on that.

For the rest, I'll let it go for now so as not to hi-jack this thread anymore than I already have.

Jake