Small block Chevy parts are everywhere. Most have gone through some sort of improvement through the years, while others have stayed relatively the same. The oil pump is one of those parts that haven’t been through much change. Melling just brought some innovation to the game with their Shark Tooth oil pumps – which are based on a unique helical asymmetrical gear.
The typical wet-sump oil pump uses two straight-cut gears to pump oil through the engine. Melling last year released a new gear design that resembles a shark’s tooth. The technical jargon for the new gear is actually a helical asymmetrical gear.
But as Melling’s George Richmond said, “That’s a mouth full!” What exactly is a helical asymmetrical gear? Here is the breakdown on what it is and how it differs from the straight cut gear.
Helical gears have teeth that are cut at an angle and are slightly twisted. Straight cut gears collide into full contact. Unlike the straight cut gear, the angled teeth on the helical gear gradually become engaged with one another. The result is quieter and smoother operation. Most manual transmissions have straight cut reverse gears causing a high pitched whine in reverse. On the other hand, ring and pinion gears are helical cut and provide much quieter operation.
Asymmetrical refers to the sides of the teeth. Each side of a tooth is called a profile. When the profiles of a tooth are not identical, it is considered asymmetrical. The gears in an oil pump are always spinning in one direction. Therefore, one side of the tooth is experiencing higher loads for long periods of time. This side of the tooth is improved by degrading the opposite side of the tooth resulting in different tooth profiles.
The smooth operation of the helical asymmetrical gears has reduced pulse ripple compared to the straight cut gears. Pulse ripple is a pulse in pressure as the pump operates. Melling cites improvements in timing component wear, spark scatter, and less stress on the intermediate pump shaft as the result.
Melling also improved the tip of the gear teeth to create a tighter seal with the pump housing. Melling states that this improvement has increased vacuum inside the pump resulting in increased efficiency and faster priming.
So far the new design is only available for the Small Block Chevy, although there are standard and high volume versions available. A billet aluminum version is also available for racing applications.