Deciding on the best oil pump for your Gen 3 Hemi can be daunting - Here's how

SDPC Tech written by Jesse Smith

 

There are are so many different oil pumps for the Gen 3 Hemi that it can be overwhelming to decide which one you want and why.   Lucky for us, the information is out there, so we're going to dig though it all and compile them for you.  

• Which one of the available Melling part numbers is best for what I’m doing?
• What are the differences in the various Melling oil pumps?
• Can I use the Hellcat oil pump in my 5.7 or 6.4?
• Is the Hellcat oil pump better or worse than the Melling?
• Which Melling is the Hellcat equivalent?

If you’re unfamiliar, you should know that Melling manufactures the factory oil pumps.  In regards to quality, you should have no concerns regarding Melling VS OEM Mopar. Melling is a premier OEM manufacturer of  not only oil pumps, but many OEM engine parts.  Here at SDPC, as both GM and Mopar dealer and a huge aftermarket parts supplier for brands like Melling, we have quite a bit of experience with all of them.

Let’s chart the main differences between the pumps.  Once you know the differences, the decision on what’s best for you should get much more simple.  Don’t forget, if you need help, just contact the professionals at SDPC any time for a recommendation.

Let’s start with factory replacement pumps.  If you have a factory engine and simply need a replacement oil pump, both Melling and OEM are great choices.

09+ 5.7 Hemi – 53021622BH

09+ 6.4 Hemi – 5038398AE

Hellcat 6.2 – 68195993AD

That’s easy enough, but what if you’re looking to upgrade or buy a stock replacement Melling to save some money?

Melling part number M452 is a stock replacement pump for the 5.7 and 6.4 engines.  It will be the same pressure and volume as the factory pump.  This is a great choice for pretty much any factory rebuild or simple pump replacement.

Wait, Volume AND pressure?  Yes, there are two factors to consider when upgrading your pump.  Depending on your situation, you might find that what you are looking for when you upgrade is higher volume, not higher pressure.  If you have an aftermarket built engine with lower pressure than you like at idle and part throttle, a higher pressure pump will not generally be the solution that you are looking for.  No, we’re not crazy.  Typically the lower pressure comes from larger clearances in the bearings, axle-oiling lifters, etc, and a higher volume of oil is necessary to feed your engine what it needs in order to increase the pressure.

Why is it not a higher pressure pump that you need to get higher pressure?  That’s a really good question. Let’s look at what those terms actually mean inside your oil pump, or (insert link “Click here to skip to the differences in Melling pumps”)

Higher pressure:  The high pressure rating of an oil pump is determined by the bypass spring inside the pump and it regulates maximum oil pressure.  Over a certain pressure (determined by the bypass spring), the bypass valve opens and dumps the oil back into the pan before it gets to the engine.  High pressure pumps simply have a higher pressure spring installed the bypass.  Below the bypass pressure the pump does nothing different than stock, so in idle and lower rpm situations where you don’t make enough pressure to open the bypass spring, a higher pressure pump will not change your oil pressure.   A Melling high pressure pump comes standard with a +10psi spring installed, and they include a stock spring if you want to go back down in max PSI.

Higher volume:  A pump’s volume is determined by the displacement of the rotors inside the pump.  By making a pump thicker or varying the geometry of the internal rotors, the manufacturer varies the amount of oil pumped with each revolution on the pump.  A higher volume pump moves more oil with each revolution of the pump.  This means that a higher volume pump will move more oil at any given speed, therefore reaching the pressure of the bypass spring sooner. 

Let’s not get crazy, too much of either one is not a good thing.  Everyone wants oil pressure as high as possible in any given situation, right?  Why not just get the highest volume and pressure possible?  Higher pressure and volume can cause issues such as oil leaks, high oil temperatures, pumping losses for no valid benefit if you’re exceeding the amount of oil the engine needs (pumping uses horsepower after all), etc.  We could even get into oil pump cavitation at high RPM in a gearotor style pump, but lets just settle on the fact that you can have too much of a good thing.   

Anyways, what are we here for?  Oh yeah. The Melling pump upgrades and how they relate to stock pumps.

As noted, the M452 pump is a stock replacement for the 5.7 and 6.4 engines.

Mopar 68195993AD.  The infamous Hellcat oil pump, many people’s first thought when upgrading their 5.7 or 6.4 pump.  The Hellcat pump provides 12% more volume over your stocker and the M452, and it has a slightly higher pressure (approx. 2psi) relief spring installed.  This pump is available under Melling part number M452HV.

Melling M452HV.  As noted above, this is the Melling part number for the Hellcat oil pump.  It is 12% more volume than the M452.

Melling 10452. We’re getting into aftermarket performance pumps now. The 10452 is standard volume with a 10-12 psi higher than stock pressure relief spring. It also includes a stock pressure bypass spring.*  The case is hard coat anodized and the front cover is phosphate coated for added durability. 

Melling 10452HV.  The 10452 HV combines the 10-12psi over stock bypass spring with the 12% higher volume of the Hellcat pump.  It will also include the stock pressure spring in the event that you want higher volume with stock maximum pressure.  You get the benefit of the hard coat anodized body and phosphate coated front cover for durability as well.

*The higher pressure Melling spring opens the bypass at 75psi.  The spring referred to as stock pressure opens the bypass at 65psi.