While oil pumps may live a life of obscurity, it’s worthwhile to spend a little time choosing the right pump for your application. Melling has a new line of Shark Tooth pumps that promise greater performance through an improved gear design.

Words and Photos By Jeff Smith

Oil pumps don’t get a lot of love. It seems the only time they get attention is when something goes wrong. But, like your heart steadily beating inside your chest, the oil pump is what keeps that lifeblood of oil coursing through your engine, keeping everything lubed and cool. So, when it comes time for that next performance engine, it’s worth it to put a little thought into the oil pump and what it does. That’s what Melling’s engineers have done to come up with a new twist on the small-block Chevy oil pump.

Melling calls it the Shark Tooth pump. Essentially, it’s a helical twist into the ancient small-block Chevy straight-cut gears that offers numerous advantages. Let’s start by looking at what that oil pump really does. While your oil pressure gauge happily reports a stable idle of 25 psi for example, it’s really only reporting a highly damped version of what’s really happening. Dampening makes the needle nice and steady, while the actual pressure might be fluctuating 10 to 15 psi on either side of that median number. If your gauge was not heavily damped, you’d see that needle fluctuate wildly.

Melling’s new Shark Tooth version (left) of the traditional small-block Chevy oil pump may not look much different on the outside except for its phosphate coating, but there’s a whole lot going on inside that can pay off in better performance.

Now, let’s spin our engine with its straight spur gear pump up to 6,000 rpm. Since the pump is driven off the camshaft, it’s spinning at half engine speed, but the oil pressure is still madly oscillating. Melling’s tests reveal that stock pump pressure can fluctuate as much as 150 psi between its peaks and valleys on its way to generating an average damped pressure of 60 psi, for example. These wild oscillations create significant load changes on the camshaft and especially the distributor gear. This occurs anytime the engine is running.

All high volume pumps employ taller gears (left) to move more oil compared to a standard version (right). This photo also clearly shows the helical asymmetrical design difference for the ST gear compared to the straight spur gear (right). The Shark Tooth name originated from its asymmetrical tooth design that looks like a shark’s fin.

The big advantage to the Shark Tooth helical asymmetrical gear design is it dramatically dampens these pressure fluctuations. They are still present, but the oscillation with the Shark Tooth gear design reduces the peaks and valleys by an amazing 70 percent. This immediately reduces the load imparted into the camshaft, which results in a significant decrease in cam and distributor gear wear and potentially more accurate ignition timing.

The Shark Tooth design increases the relative gear tip position to the housing that increases volumetric efficiency, which then improves the flow rate.

Prior to the Shark Tooth’s introduction, Melling offered an extended family of oil pump options for the small-block Chevy. The Shark Tooth versions carry the same part numbers, just with the additional ST suffix. So, if you already have a favorite Melling pump, the only thing that changes is the ST suffix. You can actually feel the difference in the Shark Tooth just by spinning them by hand. The Shark Tooth design is a Melling innovation that is the first use of asymmetrical gears in an oil pump.

Oil pressure gauges are highly damped. The inlet hole on a typical mechanical gauge is very small. If you substitute a -4 instead of the usual 1/8-inch line, you’ll notice the gauge is much more active because it is less damped. That’s because a standard spur gear pump fluctuates wildly. This graph shows the radical difference in pressure fluctuations between a stock and Shark Tooth pumps. This test was performed at a 3,250 rpm pump speed, which would be 6,500 engine rpm.

The advantage of the asymmetrical design is each side of the gear is not a mirror image. By becoming asymmetrical, the gears effectively have a long and a short side, making them directional like a tire on a car. This creates a drive and driven gear, which improves the operating tolerance between the gears. The original spur gears are identical and therefore do not operate as efficiently. In addition, this gear design also reduces the operational clearance between the gear and the pump body. This reduces internal leakage to improve performance, while also reducing oil temperature.

This comparison of the pump inlets reveals a couple of important items. Standard small-block pumps use a 5/8-inch inlet. An optional ¾-inch inlet reduced restriction, which improves pump efficiency. ST pumps (left) also offer the option to use either a press-in or bolt-on pickup while standard pumps only use a press-in pickup. The fasteners can also be safety-wired or tack welded to the pump for additional insurance.

With this broad range of ST configurations, there’s an application for just about any small-block Chevy.  You can order a Shark Tooth pump with stock volume output or with either a 10- or 25-percent increase in volume. Higher volume pumps achieve this capacity by increasing the depth of the pump body and extending the length of both gears to move more fluid. Each of these new pumps is also optioned with additional pressure-relief springs that offer the latitude to custom tailor the pressure. Finally, each pump also comes with a specific 12550 Chromoly steel oil pump drive shaft. This pump drive is designed specifically to mate into a recess in the pump drive shaft and connect with the end of the distributor.

The 10555 pump offers this slick Allen plug that makes changing the oil pressure relief spring extremely simple. Melling offers three different springs with a 20- to 30-psi pressure range.

In the quest for the ultimate wet sump oil pump, Melling has also been building a line of patented billet aluminum pumps that now includes Shark Tooth versions. These billet aluminum versions fit into the same space as the original cast iron designs and offer a measurable weight advantage (1.75 pounds lighter), along with a pickup that is integrated into the pump body to eliminate issues from cracked or broken pickups.

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Stage II pumps (10552ST and 10555ST) are also fitted with extended shafts that locate in the pump cover (a patented Melling innovation) to minimize gear deflection and improve efficiency.

These Stage III billet ST pumps offer all of the advantages of the straight spur gear designs combined with the Shark Tooth’s significant improvements. There are three different configurations for these ST billet pumps designed for 7-inch circle track or 7.5-inch and 8.25-inch street-strip pan depths. These pumps are offered in either standard or high volume and include a selection of different pressure springs.

The small-block Chevy recently blew right past its 60^th birthday showing no signs of falling back into its rocking chair of retirement anytime soon. This little engine will continue to perform as long as companies like Melling keep building better parts that promise more power and improved durability.

Source: Melling Automotive Products, melling.com