How to Install a High Press Spring in a Small Block Oil Pump

  1. krazykuda
    Hello folks! Krazykuda here to show you how to install the MP high pressure spring in the small block oil pump. This will work for all oil pumps for the 273-318-340-360 LA engine.

    Some people like to run higher oil pressure, and some don't. This is for those who choose to run a little more oil pressure than "standard" stock pumps put out. For those of you who don't buy into increased oil pressure, please move on and not leave any negative comments.

    Use this information at your own risk. If not done properly, your oil pump can fail which can potentially destroy an engine. I cannot be held responsible if this is not done properly.

    For this thread I will be using the Melling M-72HV high volume oil pump shown below:

    HP Oil Pump A02 B.jpg

    Next you will need the Mopar Performance Spring Kit P/N P3690944:

    HP Oil Pump A03 B.jpg

    Here it is shown from behind so you can see. It only has the spring and cup plug that you will need. It USED to come with a cotter pin, but they "cost reduction" that out now, so you may want to get a spare cotter pin or two in case you can't save the original one:

    HP Oil Pump A04 B.jpg

    Here are a few different angles for the oil pump:

    HP Oil Pump A05 B.jpg

    HP Oil Pump A06 B.jpg

    Here's the view showing the part that we will be working with. Notice how the cup plug faces inward, not outward like the cup plugs in the blocks and heads. This is important, as putting it in backward will greatly increase your oil pressure (probably WAY too much):

    HP Oil Pump A08 B.jpg

    Here's the tools that we will need. Notice that there is no drill and drill bit shown. You DO NOT WANT TO USE A DRILL HERE! The chips that it generates can cause the oil pressure relief valve to stick and then there will be NO OIL PRESSURE in your engine. We want to punch a hole in the cup plug to keep from making chips that can cause the valve to stick. It only takes one chip to do it...

    HP Oil Tools A01 B.jpg

    I like to get an assortment of screws and washers to handle whatever size hole I end up with and different lengths in case I accidentally drive the cup plug deeper when trying to punch the hole:

    HP Oil Tools A05 B.jpg

    Here's what I use to punch a hole in the cup plug, and then use the hook on the right to help fish out the pressure relief valve:

    HP Oil Tools A03 B.jpg

    Ok, now we are going to move on to removing the old spring....

    Ok, now we are ready to remove the old spring.

    The first thing to do is to remove the cotter pin. Pretty simple, just straighten the bend at the bottom as shown below:

    HP Oil Pump A10 B.jpg

    Here the cotter pin has been removed. Note the cup plug orientation with the lip facing inward, not outward. You need to put it back together like this:

    HP Oil Pump A12 B.jpg

    Next take a punch or scratch awl and punch a hole in the cup plug. You want to use a medium weight hammer with a SHARP blow. Not lightly as it will just push the cup plug deeper and not make the hole. A quick sharp blow is what you need here. Don't be afraid to give it a good whack, take off your panties and put on a pair of tightey whiteys for this....

    Here's what you want it to look like:

    HP Oil Pump A14 B.jpg

    Now get those screws and washers that I showed you in the first post and see if one of the screws will start in the hole. If not keep opening up the hole with the punch/scratch awl a little bit at a time until you can get the screw to thread into the cup plug like this:

    HP Oil Pump A17 B.jpg

    Use one of those split interior trim removal tools/pliers/vise grips to remove the cup plug with the screw and washer. The washer helps you grab under the head easier to pry it out like this:

    HP Oil Pump A19 B.jpg

    Here is how the parts all go together (and the order that they come out). Notice that the valve has a deeper pocket from one end than the other. The shallow end goes into the bore first, and the deeper part goes outward toward the spring side (the spring goes into the deep side):

    HP Oil Pump A23 B.jpg

    Here I am showing the shallow side of the relief valve, this is the side that goes into the bore first, opposite the spring:

    HP Oil Pump A26 B.jpg

    Here is the deeper side of the relief valve that the spring goes into. This faces outward when you assemble it.

    HP Oil Pump A30 B.jpg

    Here's a side view of the relief valve. The shallow part is on the right. You have to keep this hospital clean, any chips and/or dust can make it stick. If it sticks, you will not get any oil pressure. Make sure it is free of dirt, debris, chips, and burrs and that it moves smoothly and freely in the bore when you install it.

    HP Oil Pump A31 B.jpg

    Ok, now move on to the next step of installing the new spring...

    Ok, now we are ready to put it back together. You have to keep everything here hospital clean. All it takes is a small chip or piece of dirt to make the relief valve stick - it has happened to me, trust me on this....

    First you put the valve in with the shallow side inward and the deeper side outward toward the spring. Use a light oil to lubricate it so it moves freely. Nothing too thick that may make it "sticky" for the first start.

    HP Oil Pump A32 B.jpg

    Then the spring and the cup plug. Remember that the lip for the cup plug faces inward. Here's showing how the parts go into the bore:

    HP Oil Pump A34 B.jpg

    Here I gently pushed them in and just have the cup plug starting to engage the bore. You want to gently tap the cup plug to get it just past the hole for the cotter pin. Go slowly, take off the tightey whiteys and put the panties back on for this....

    One step at a time. Gently tap it in a little at a time until you can just install the cotter pin. Be careful not to go too deep as this will increase the spring pressure and thus the oil pressure also. The new spring is enough, that's all we need, we don't need any more.

    HP Oil Pump A37 B.jpg

    I like to use a socket close to the outer diameter of the cup plug to drive it in without affecting the "fit" by distorting it with a sharper pointed type driver...

    My 11 mm 1/4" drive socket worked well.

    HP Oil Pump A41 B.jpg

    Here's a top view showing that I have the cup plug just deep enough to put in the cotter pin:

    HP Oil Pump A44 B.jpg

    Side view of above:

    HP Oil Pump A45 B.jpg

    Here it is with the cotter pin in place:

    HP Oil Pump A48 B.jpg

    Now bend the cotter pin (Sorry it doesn't show in this pic, but it is bent).

    HP Oil Pump A50 B.jpg

    I like to mark the pumps with paint pen or something permanent so I know that I have the high pressure spring installed so I can keep track of them.

    HP Oil Pump A52 B.jpg

    Here is a chip that fell off during our process. This one is much bigger than needed to stick that valve, all it takes is a sliver or small piece of dirt. I've seen many stuck oil pressure relief valves in my days and it doesn't take much to do it.

    HP Oil Pump A56 B2.jpg

    That's all there is to it. You have to make sure that you keep everything clean and get all the parts together correctly (not backwards).

    That's all folks...

    Here's some info that we added after some discussion that may help you:

    Ok guys & gals, here's the scoop:

    Mopar Performance:

    Both the standard and high volume pumps come with the "stock" spring.

    If you wish, you can increase the pressure with the high pressure spring kit P3690944 and it is applicable for both standard and high pressure pumps.

    The high pressure spring kit is designed to target 75 psi oil pressure (it may vary from one engine to another).

    The Mopar tech guy does not know who supplies the MP oil pumps if it is Mellings or not.

    He also can't tell me how the Melling spring compares to the MP springs.


    They use the same spring in both the standard and high volume oil pumps.

    Their spring target runs 72 psi on a standard pump.

    It will be 2-3 more psi in the high volume pump due to the increased volume will add some pressure.

    He can't tell me if they supply the MP pumps or not.

    He can't tell me how their spring compares to either Mopar spring.

    My conclusions:

    If you run the Mopar oil pumps and want more pressure, use the high pressure spring kit.

    If you run the Mellings oil pumps, you don't need the high pressure spring kit, as they are within 2-3 psi of the MP high pressure spring target....

    So that is the best that we can do to answer the pressure question. None of the manufacturers can tell us for sure..... :banghead: :banghead: :banghead:

    Side note:

    The summit racing site states:

    Melling high-volume oil pumps give you an additional 20 to 25 percent of much-needed oil volume for your performance application. For those of you who need added pressure, many pumps are supplied with a high-pressure spring where noted.

    What is this mark and where is located?

    How do we know what we are going to get when we order it?

    How do we know what we get when we open it and look at it? What are we looking for?

    I think that this is wrong. How can they randomly make them one way and then change to the other on a whim? Doesn't make sense. They should all be consistant/the same...

    Here's the page with the listing from Summit:

    I think together we can figure this out.

    The Mellings guy told me that they cast their part number in the housing near the mounting face. I found it on mine on the outside of the part of the housing where the pick-up tube goes in. I have a picture of it below.

    If anybody has either the standard or HV Mopar Performance pumps, please look for the marks on the housing for each and post back (with pics if possible - I want accurate provable info to pass on - get the part number on the box and housing ID like shown below).

    Mell Oil Pmp A02 B2.jpg

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