Volume X, Issue 3, Page 76

Chevys aren’t the only engines Titan builds pumps for. Here’s a Pro series oil pump for a Ford FE.  Included in the Titan product mix are pumps for early and late Chryslers (small and big block), Ford small blocks, Ford FE’s, Ford 460’s, Chevy big and small blocks, Oldsmobiles, Pontiacs and Cadillacs. 

Gerotor: The Moroso Option

Moroso has been supplying the racing community with oiling system components for the last 40 years.

Moroso’s lineup of Billet Wet Sump Oil Pumps feature some of the latest technology found in wet sump, oiling systems today. Their Billet Wet Sump Oil Pumps have evolved from over 40 years of experience in oil pump technology. Offering a SBC Billet “Racing” Spur Gear Pump, BBC “Sportsman” Spur Gear Pump, and BBC “Professional” Gerotor Pump, Moroso has a pump that will fit into any racer’s budget.

Each of these Oil Pumps are machined from a piece of 6061 T-6 Billet Aluminum. A durable alloy, which after being machined is hard coated, ensuring years of use. The pumps feature thrust-bearing assemblies that increase gear life and cut down on drive shaft axial forces on the gear drive; which extends the oil pump’s life. Each pump has an integral oil pump pickup. Keeping broken pickup tubes, typically caused by engine harmonics in high RPM applications,  a thing of the past. The pumps are machined with anti-cavitation grooves and enlarged bypass areas to prevent cavitation and cut down on aeration.  They also feature enlarged mounting bosses to prevent breakage.

Moroso’s  Billet Small Block Chevy, “Racing” Spur Gear Pump, weighs 1 lb. less than a stock style pump and pickup combination and it works in engines using up to a 4-1/4” stroke with most steel rods. This pump has been designed to fit into most of our SBC Street/Strip and Drag Race Oil Pans that Measure 8-1/4” deep.

Their Billet Big Block Chevy, “Sportsman Series” Spur Gear Pump, also weighs 1 lb. less that a stock style pump and pickup combination. This pump works in engines with up to a 4-3/4” stroke with most steel rods. It has been designed to fit into most of our BBC Street/Strip and Drag Race Oil Pans that measure 8” deep.

Moroso’s  Big Block Chevy “Professional Series” Gerotor Pump, features an externally adjustable bypass valve and clears 5-1/4” strokes with most aluminum rods. This pump features Gerotor Technology that has evolved from our External and Dry Sump Oil Pumps. It has been designed to fit into a Moroso fabricated aluminum Drag Race Oil Pans that measure 8” deep.
"When the fluid fills the pumping chambers in both types of pumps (spur gear or gerotor), it must be at a lower pressure inside the chamber than outside of it.  In order for the fluid to enter the pump, the higher or more viscous the oil is (a good example is cold SAE 60 weight oil), then the harder it is to get the oil through the small holes in the oil pump suction screen.  As the oil becomes warmer (and more contaminated), it tends to be less viscous and will enter the pump with less pressure drop.  Unfortunately, there's a bit more going on:  As the oil becomes hotter, the dissolved (or emulsified) fuel contamination becomes much closer to changing itself from a liquid state to a gaseous state (at this point, the fuel contaminants in the oil expand approximately 300 times).  Remember that the pump is now pulling a vacuum reading on the oil, drawing it into the pump body.  What the pump is pulling is a combination of oil and gaseous bubbles.

"This is where the two types of pumps differ.  The gerotor configuration has four lobes on the drive, which take a little over 180° of crankshaft rotation to fill the pumping chamber.  Meanwhile, the spur gear design (using a 12 tooth gear configuration as an example) has only 60° of crankshaft rotation to accomplish the same thing.  Since the gerotor has more than three times the work time to fill it's chamber, it allows the oil to accelerate smoothly into the pump chamber, then shut off slowly as it completes it's cycle.  This smooth action is less likely to pull gas out of the entering fluid than a spur gear pump, which is trying to fill the chamber three times faster (this is like shaking a soda can before you open it).  At 9,000 RPM, the spur gear pump is trying to fill itself 54,000 times per minute.  Meanwhile, the gerotor is trying to fill itself at 18,000 times per minute."

What is Pump Cavitation?

Most racers understand that pump cavitation isn't good.  In fact, it can be damaging to both your engine and your wallet.  What really happens when a pump cavitates?   Sanders offers these explanations:

"Cavitation is always destructive -- especially to objects that are near to it.  Cavitation is what occurs when a gas is forced back into a liquid state. Basically, it's imploding bubbles.  This causes the horsepower required to drive a pump to increase by three to five times.  Meanwhile, the oil coming out of the discharge of a pump drops to between 10-20 percent in volume.  The total volume of the oil and the gas bubbles combined is often higher which can make pressure measurement fool you.

"To compare how the two pumps discharge oil, you can see how the gerotor inherently is much less likely to cavitate.  Again, the spur gear takes the same 60° of crank rotation to hammer the oil (and bubbles) up to the selected by-pass pressure.  The gerotor design discharges three times slower and smoother, through the 180° crank rotation.  Significantly fewer bubbles implode if you squeeze them slower."

There is only one advantage to a very large pump that doesn't cavitate upon acceleration.  But it's a big one:  This type of pump oils the bearings before the load is on them instead of after.  Basically, both a spur gear and gerotor pump put the same amount of oil into the lube system at a given pressure if there is no cavitation.  Either configuration will only pump oil if there is oil in the pan.

Bypass Surgery…

That brings us to the bypass circuit.  Sanders explains:

"By design, the bypass in a spur gear must be discharged back to the pan.  This translates into lost energy.  If the bypass in a spur gear pump was internal, this pump configuration would cavitate itself into destruction.  On the other hand, the bypass system in a gerotor can be configured to pump into the upper field (suction stage) kidney.  This basically supercharges one end of the suction stage which reduces the load on the pump drive -- especially at high RPM.  Further to this, in tuning the shape and volume of the suction and discharge kidneys we set them up to so that they are technically "On The Cam" at 4000 to 12,000 RPM's. We call it Progressive Pulse Technology."