Frequently asked questions
What is a Dry Sump Oiling system?
Dry sump systems are designed to provide better oil control and higher engine performance over the standard wet sump system. To understand why a dry sump system is preferable, it’s important to understand the basic functionality and limitations of a wet sump system.
Most internal combustion engines use a wet sump oiling system. A wet sump system is a simple, cost effective, self-contained oiling system. In a self-contained system, all components are integrated into the engine. The defining component of a wet sump system is the large oil pan, also known as the sump. The oil pan is the lowest part of a traditional engine and is designed to contain the oil after the oiling cycle is complete.
Oil containment is critical for engine function on a wet sump system. The oil pickup tube located in the lowest part of the oil pan must always be submerged in oil. If the tube becomes uncovered, air will enter the pump causing a loss in oil pressure. This will result in engine damage, or worse, total engine failure. In racing, there are extreme external forces in action that cause the oil to shift around in the pan, exposing the pickup tube to air. To prevent this, significantly wider and deeper aftermarket oil pans with elaborate baffling are installed in attempt to keep the pickup tube submerged in oil. Accommodating this larger pan requires extra space under the crankshaft, reducing ability to lower the center of gravity of the vehicle. This represents one of the major drawbacks of a wet sump system in racing, and a major advantage of a dry sump system.
With a dry sump system, the oil pan is not used for oil storage. Instead, the pan is specifically designed to be as thin as possible, while still effectively scavenging the oil that is suspended in the windage generated by the crankshaft. Oil is stored in an external reservoir eliminating the risk of oil pump starvation caused by the extreme G-load effects during racing. With the use of a thin dry sump oil pan and remotely mounted oil tank, the engine can be lowered in the chassis to improve the handling characteristics of the vehicle.
Most commonly, a dry sump pump comprises two separate pumps built on a common drive shaft. The first pump is the pressure pump. This is what replaces the internal pressure pump of a wet sump motor. The second pump is the scavenge pump, which is normally made up of multiple stages. These stages vary in number and length depending on the application. For example, in a road race application you will typically find one stage per bay of the oil pan, and the size of each stage will depend on desired crankcase vacuum. Configuring a dry sump pump specific to the application with the ability to generate crankcase vacuum can result in a significant increase in engine performance.
1) The low profile pan in a dry sump system allows the engine to be lowered in the chassis for better handling.
2) No more oil pump starvation issues caused by forces acting on the oil during racing.
3) A properly designed dry sump system can improve engine performance.
What is pump cavitation and what causes it?
Cavitation is the formation of voids (vapor bubbles) within a liquid, caused by rapid decrease in localized pressure on the liquid at the pump inlet as the pumping cavity opens. As the fluid passes through the pump the pressure increases causing these voids to implode resulting in a shockwave. These shockwaves are powerful enough to cause pitting and erosion to the surface of the pumping gears, decreasing its performance and longevity. As cavitation worsens, the pump outlet pressure can no longer be maintained.
The local pressure drop that causes cavitation is a factor of both fluid restriction and pump speed. Restriction can occur at the pump inlet due to an undersized feed line, restrictive fittings, or high oil viscosity. As pump speed increases, it’s harder for the oil to fill the pumping cavities quickly enough to prevent a local pressure drop.
Why would I want to make crankcase vacuum?
The number one advantage for crankcase vacuum is power gain. This is achieved by using low tension piston rings to reduce friction without losing an effective ring seal, and by evacuating the blow-by gases that resist piston movement.
When determining an optimal vacuum level for power gain, it’s important to consider the application and needs of the engine. The more vacuum generated means more power it will take to turn the pump, so an increase in vacuum will not necessarily result in more power if the engine isn’t designed to take advantage of this potential power gain. If the engine has force induction with high boost, crankcase vacuum will be much harder to achieve and might be more benificial if vented to atmosphere.
For example, optimal vacuum level for a sports car in endurance-type racing is approximately 12-14in/Hg. This level is higher in top-level Pro Stock drag racing, where levels are pushed upwards of 25in/Hg.
How do I seal the engine to make crankcase vacuum?
All vents on the valve covers and valley, as well as any other air-sucking orifices, should be plugged. The front and rear main seals should be upgraded if a vacuum over 15in/Hg is desired. A vacuum regulator should be installed and set. Some regulators act as a one-way pop off valve in the event that the crankcase goes positive in pressure. On high power applications, or when using a vacuum regulator that doesn’t have a built-in pop off valve, we recommend installing a stand-alone pop off safety valve on the valve cover in addition to the vacuum regulator.
How do I plumb my dry sump system?
Using the oil tank as a starting point:
● From the outlet fitting at the bottom of the oil tank, run a -16 unrestricted line to the inlet fitting on the oil pressure pump. This line should not have any filter or restrictive fittings installed. Typical fittings installed are -12 ORB to -16 Flare with a minimum I.D. of 7/8”
● From the pressure outlet fitting on the oil pump, run a -12 line to an optional oiler cooler (if using an oil cooler the flow must be equivalent to a -12 line size (5/8" ID) to minimize pressure drop) then run to a remote engine oil filter. Typical fittings installed are -10 ORB to -12 Flare with a minimum I.D. of 5/8”
● From the remote filter, run a -10 or -12 line to the engine block oil feed fitting (for OEM style blocks use -10, for aftermarket blocks with -12 female port use -12 line). If the remote filter is mounted farther away from the engine block feed fitting (36” line or longer), then a -12 line should be used then adapted down at the block if the inlet fitting is a -10.
Typical fittings installed are -10 ORB to -12 Flare with a minimum I.D. of 5/8” OR -10 ORB to -10 Flare with a minimum I.D. ½”
● From the scavenge outlet fitting on the pump, run a -16 line to a 75 micron scavenge canister filter before returning to the oil tank. For high vacuum applications there could be two scavenge return lines or single -20.
Typical fittings installed are -12 ORB to -16 Flare with a minimum I.D. of ⅞”
● From the vent at the top of the oil tank, run a -16 vent line to a catch can. The breather filter on the catch can should have a large surface area to allow for proper tank ventilation. Typical fittings installed are -12 ORB to -16 Flare with a minimum I.D. of ⅞”
● Some pumps will have additional sections to scavenge heads, valleys and/or turbos. These scavenge lines should have 730 micron screen filters installed to protect the pump from any debris.
Here is an example plumbing diagram
How tight does the HTD belt need to be?
Don’t panic the first time you install our dry sump! The belt runs in a loose condition, so you should be able to roll the belt off the pulley easily but not skip a tooth. You should be able to twist the belt 90 degrees. Never pinch the belt together as this can generate a tremendous amount of bending load on the shaft.
How do I adjust the oil pressure on my Dailey Engineering pump?
There are two different types of oil pressure to consider with a dry sump system.
1) Idle oil pressure. This should be measured when the engine is at operating temperature. This pressure is a function of the pump speed ratio, the pressure gear size in the pump, the viscosity of your oil and the flow demand of your engine. There are two ways to adjust this pressure. The first and preferred option is to change the size of the pressure gear in the pump. The second option is to change the pump speed relative to the engine by changing the belt and pulley combination to increase or decrease oil flow. This option has an effect on the scavenge side of the pump as well, so an increase or decrease in pump speed will affect vacuum pressure.
2) RPM oil pressure. This pressure is a function of RPM and the bypass valve spring rate on the oil pump. When the oil pressure reaches the pressure that the bypass spring is set to, the valve will open gradually and level off at that pressure. To adjust the pressure, you need to loosen the jam nut on the set screw then turn the set screw in to increase pressure. Each turn will be 7psi at the pump exit for a maximum of two turns in and three turns out. If a more drastic change is needed, you will need to change to the next spring rate. See illustrations.
It’s up to you as the engine builder to determine optimal oil pressure for your application. A good rule of thumb is 10 psi for every 1000 RPM engine speed measured in the oil galley.
What size oil tank do I need?
The oil tank serves three main purposes – it's a reservoir for the oil in the system, de-aerates the oil, and vents off all blow-by gasses that have been evacuated out of the engine. A tall, small diameter tank with a large breather is ideal. This will allow for a large column of oil over the pickup and the maximum amount of time for the blowby gasses to separate from the oil.
We recommend a 6” diameter 2.5 gallon tank for most applications. This tall, small diameter, tank is ideal for giving time for deaeration, venting, and handling g-loads but being that it is 24” tall it can be tough to fit in some race cars. If a shorter tank is required the next best tank would be a 6” diameter 2 gallon tank, still a small diameter but only 19.5” tall. For a drag racing application, the oil doesn't cycle through the system enough for aerating to be a major factor but venting blow-by gasses is critical so we recommend a tank that has large breathers and two large scavenge return sections.
Can I mount the oil tank in the trunk of my car?
Yes. The plumbing size from the tank to the pump will need to be increased to minimize the pressure drop and reduce the chance of pump cavitation. We recommend a 1” I.D. hardline from the rear of the car to the front bulkhead then to a -16 hose to the pump inlet.
What level should I fill my oil tank to?
The level in the tank should be at around ⅔ when the engine is running. This should just be under the top baffle.
How do I convert my LS7/LS9 OEM dry sump engine to a wet sump style to use the Dailey Engineering dry sump systems ?
The Dailey Engineering dry sump systems are designed to fit the LS2/LS3 wet sump front timing cover. To convert your OEM dry sump style engine, you will need to replace the front time cover, pan gasket, and timing chain set. The snout on the OEM dry sump engines are longer than the wet sump engines so an ATI spacer will be needed after the ATI damper is installed for the crank bolt can clamp down properly.
See the LS7 to LS2/LS3 conversion parts guide PDF for more info.
How do I vent my engine if i'm not trying to make crankcase vacuum?
If vacuum is not desired, the crankcase should be vented to atmosphere. The simplest way to achieve this is by installing a vacuum regulator that is set to its lowest setting (in case you want to run vacuum later), or use a baffled vent on the valve cover.
Another option is to plumb the valve cover to the oil tank catch can using a -12 or -16 line. In high blow-by applications, or when the valve covers are not baffled properly, oil may fill up the catch can over time. In this scenario, it’s better to vent the valve covers with a baffled vent as stated above, or to plumb the valve covers to the second scavenge return fitting on the oil tank (oil tank must be a dual scavenge return style). This will allow the oil being carried by the blow-by gasses to settle out in the tank before heading to the catch can.
How do I prime my system for the first time?
Once everything is installed, you will need to prime the oiling system before starting the engine for the first time. To do this, fill the tank to the top baffle, loosen the oil pressure feed fitting on the block, slip the oil pump belt off of the pulley. Next, rotate the pump by hand or with a drill (NOT AN IMPACT DRIVER) until all the air is pushed out of the loose fitting and oil starts to flow out. Then, tighten the fitting and rotate the pump again until you feel it bog down. Check all lines for any leaks and ensure the oil tank is about ½ full, then reinstall the belt. The engine is now ready to run. Once the engine is running and warm, fill the tank to the ⅔ level.
As a ballpark estimate on volume, you can assume tank volume equals total oil volume. For example, a two-gallon tank will use approximately two gallons of oil in the whole system – but it could use more if the oil tank is in the trunk, or it could use less if you are not using an oil cooler.
What is a bypassing oil filter and why would I need one?
The bypass (relief) valve is an integral part of the oiling system. Bypass valves are designed to allow oil flow to the engine components when the oil is cold, or if the filter becomes clogged. Bypass valves can be located in the oiling system or in the oil filter itself.
Under normal operating conditions, the bypass valve will not be open. When the bypass valve does open, the oil flows directly to the engine to prevent oil starvation and damage to the engine components.
There are two conditions that will cause the bypass valve to open:
Engine Starts - When the engine is started and the oil is cold. Cold oil does not flow through the filter element as freely as when it is warm. This causes the pressure differential across the filter element to increase and the bypass valve to open. The by-pass valve will close once the oil is warm and the pressure differential across the filter element drops below the bypass valve pressure setting.
Plugged Filter – A filter will become plugged if the oil is contaminated, or the filter is not serviced regularly. Once the filter becomes clogged, the bypass valve will remain open. This allows unfiltered oil to lubricate the engine components, preventing engine damage from oil starvation.
If there is no bypass valve installed it will be possible for the oil filter to blow off from the high oil pressure. This can result in engine failure and a possible oil fire.
Some engine builders choose to not have a bypass in the system to guarantee that oil will always pass through the filter element but it is critical to warm the oil to operating temperature before the engine is started and the filter is changed after every run.
How do I print a PDF drawing full scale?
Open the file in Adobe Acrobat or Adobe Acrobat Reader and set the zoom to 100%. Move the drawing to the view you want to print. Click File/Print or Ctrl+p to access the print menu. In the print window under "Pages to Print" select "More Options" and click the Current View button, then under "Page Sizing & Handling" select the Actual Size option. Click Print and verify that the drawing is full scale by measuring a known dimension on the drawing. Inkjet printers seem to be more accurate than some laser printers.