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Should the oil pan be installed after buttoning up rotating assembly and installing the oil pump and pickup? Or is it a better practice to bolt down the oil pan after the long-block is fully assembled and the intake manifold is in place?
Installing the pan the right way will guard against leaks and improve durability and performance.
It’s not a trick question, or a foolish one. There are schools of thought from both logical and convenience perspectives that give credence to both procedures. But the question is posed to raise awareness that installing the oil pan is not a simple matter and deserves proper attention when the time is right. To that end, EngineLabs worked with Moroso to compile a number of useful tips to ensure the lifeblood of your engine is secure. The focus will be on wet-sump systems, but some tips can be applied to a dry-sump.
With anywhere from five to nine quarts of oil in a typical performance V8 engine, and even more in diesel applications, the chance for an oil leak is always present. And no one wants an oil leak, whether it’s messing up the garage floor or presenting a hazard on the track.
Our experience is that many leaks are directly traceable to poor gasket quality. – Thor Schroeder, Moroso
Conventional wisdom says a trouble-free oil pan installation starts with planning and attention to details. Do you have the right part number for your application? Have you changed anything on the chassis that might interfere with a pan designed for your application? Is the oil-pump pickup is a correct match to the pan?
Then come all the supporting parts, such as gaskets, windage tray and mounting hardware. Plus, don’t forget you need a dipstick and tube, even if your engine has provisions in the block or front timing cover.
Check That Clearance
Oil-pan manufacturers usually have dedicated pickups for specific pans, especially for deep sumps or pans that move the sump away from the pump to clear chassis components. But it’s always a good idea to double-check the pickup-to-pan clearance.
“If the oil pump pickup is too close to the bottom of the oil pan, the confined area can pinch off and restrict flow,” warns Moroso’s Thor Schroeder. “When the pickup is too high in the oil pan, the pickup may suck air under hard acceleration, cornering or braking.”
Moroso offers dedicated pickups to provide the proper clearance with specific pans. Note that the pickup is brazed in place for added security. Sometimes, the pickup brace or other supports may have to be notched to clear windage trays or hardware.
Moroso recommends that the bottom of the pickup be positioned 3/16- to 1/2-inch away from the pan floor. GM products are usually around a quarter-inch while Ford products generally need up to a half-inch, according to Moroso.
“With variation in paper rail gaskets and 1-piece silicon gaskets, there will be variation in pickup clearance,” adds Schroeder.
Pan-to-pickup clearance can be checked by measuring or with modeling clay. Here the distance from the engine block to the bottom of the pickup is measured with a ruler and straightedge.
There are two methods of checking pan-to-pickup clearance: clay and rulers. The first involves placing a small ball of modeling clay on the pickup, then snugging down the pan with the gaskets and seals in place. Remove the pan and check the depth of the clay with a machinist’s ruler or depth probe on a dial caliper – much like you would do when checking piston-to-valve clearance with clay. The other method is using a straightedge and ruler to check the depth of the pan and the distance from the block to the bottom of the pickup. Be sure to have the gasket on either the pan or the block when making the measurements. Then subtract the pickup measurement from the pan depth.
“If you are using a Moroso press-in type extended oil-pump pickup with your Moroso pan, it is recommended that you have the pickup brazed to the oil pump housing,” suggests Schroeder. “This step eliminates the possibility of the pickup coming out of the pump due to vibration.”
Moroso recommends that the pump bypass assembly and end plate be disassembled when applying high amounts of heat to the pump housing.
Gaskets Or Sealant?
Fed up with any number of reasons that gaskets leak, some engine builders took a cue from the OEMs and laid down a full bead of RTV silicone (never use bathtub caulk!) to seal all the gaps between the pan and block. Or did the OEMs pick up this trick from racers? Either way, eliminating gaskets in favor of a sealant kept the oil inside the pan, but it was a pain in the butt to service the bottom end of the engine in the pit. Yes, sometimes there is too much of a good solution.
Molded, 1-piece gaskets provide the best protection against leaks. They are installed dry, although many engine builders add a dab of RTV in the corners on the block side. Note the metal inserts to reduce the chance of overtightening.
Gaskets have improved significantly, especially with the introduction of composite and rubber materials, pretty much eliminating the need for any type of silicone treatment. They’re certainly cleaner and easier to install than silicone, and a gasket can be more forgiving to surface preparation. On the plus side for RTV, it can work if you don’t have the right gasket handy.
“Be sure to use OEM quality gaskets or equivalent. Moroso offers a full line of 1-piece reusable silicone gaskets for most OEM applications,” says Schroeder.
RTV sealant is popular with many engine builders, and it's the preferred sealing method by many OEMs.
Consider the Ford 7.3-liter Powerstroke engine that comes from the factory with silicone sealant. Moroso offers a new reusable oil pan gasket that features steel inserts in the bolt holes to prevent the gasket from being overtightened.
“Why would the mechanic wait for silicone to set up or the chance that the surfaces weren’t prepped when this gasket takes care of those issues,” asks Schroeder.
Multi-piece gaskets are a low-cost option but not always recommended for performance applications. It's a good idea to use silicone at all the mating points in the corners.
Moroso does suggest that a dab of silicone at the corners when using Moroso gaskets can help guard against leaks in sensitive areas. And if the engine builder is using multi-piece oil-pan gaskets and seals, penny-pinching is not a good habit.
“Many off-brand, multi-piece gaskets are especially poor in the rubber-end seal area. Our experience is that many leaks are directly traceable to poor gasket quality,” says Schroeder. “We highly recommend replacing multi-piece oil pan gaskets each time the oil pan is removed. This will guarantee the integrity of the gasket.”
Proper Preparation
Be sure the rails on the block and pan are wiped clean before positioning the gasket.
Both the block and pan surfaces must be clean and straight. Be careful when removing old stubborn gasket material or RTV. Don’t gouge the block’s rail surface, especially on alloy blocks, when using a putty knife or similar tool. Check all the bolt holes as some may need a wire brush or even chasing with a tap. If reusing hardware, clean any sealant or surface corrosion with a wire brush. Here’s another quick tip: count all your fasteners before starting the installation.
Similar attention is needed on the pan. Use a flat, solid surface to check for straightness, then clean the rails and bolt holes. If pan is chrome plated, brush out the drain hole threads to clean any leftover flakes that could start a leak. If the pan has internal trap doors, check their operation. In fact, some engine builders install these types of pans with the engine block in the upright position, just to make sure a door is not stuck in the open or closed position.
Hardware And Tightening
The choice between bolts or a stud kit is generally a matter of convenience and budget, but there may performance considerations in some applications.
“Studs and nuts are available to fit in areas that bolts can’t,” says Schroeder. “With studs, the installer is able to get a more accurate torque reading when tightening the oil pan to the block than when using bolts.”
Pans can be secured with studs and nuts or bolts. Each has their pros and cons, with studs being more accessible and bolts being less expensive.
Studs Or Bolts?
Studs do protect the mounting holes in the block and speed up installation/removal, which is important to racers who often service their engines between races. The studs should not be overly tightened in the block, and it’s a good idea to use a dab of thread locker.
“Some oil pans will work better with bolts, while others are better suited for studs and nuts, particularly aluminum oil pans,” adds Schroeder.
Confirm the pan manufacturer’s torque specs if using the company’s hardware, or check the literature from the fastener company. Some applications require the different torque specs for the corner bolts.
Conventional tightening procedure calls for tightening down the four corners to about 50 percent of torque. Then start tightening the center bolts to 50 percent and moving outward in an “X” pattern towards the ends.
Repeat this procedure at 75 percent and finally 100 percent of the recommended torque. Some gaskets relax after initial tightening, so this procedure helps ensure even pressure all around.
Remember, this is your last chance to check the rotating assembly and oil pump installation. Position the gasket and apply dabs of silicone at the corners, as recommended. If using individual main seals and pan-rail gaskets, install the seals first, then position the gaskets and seal each junction point with RTV.
Snug down the corners first, then tighten from the center out in an X pattern when applying the final torque.
Final Thoughts
If using multi-piece gasket sets, focus extra attention on the front and rear seals that go over the main caps.
Installation alignment tools are helpful when positioning the pan.
“While oil leaks are a concern and are the first indication of a poor seal between the block and pan, crankcase vacuum leaks will often occur from improper gasket installation and poor preparation at the front or rear radius gaskets,” says Schroeder. “This can cause them to be sucked inward. This will cause poor performance with crankcase vacuum systems.”
Another tip when using multi-piece gaskets and RTV – use only a thin film on the block side and allow it to cure completely before installing the pan. Failure to do so may cause the gasket to slide and push out from between the pan and block.
In some cases, such as adding turbo return lines or a sensor bung, the engine builder will have to weld on the pan.
Check for leaks after welding on pan, and also be careful not to warp the pan rails with too much heat.
“Check the welds by spraying/misting soapy water on the outside of the oil pan and blowing air on the inside of the weld to see if the soapy water is bubbling,” suggest Schroeder. “The other way is to fill the oil pan with water and check for leaks. Be careful how much heat is being put into the oil during the weld process, as you don’t want warp the mounting rails of the oil pan.”
Also, rather than banging on the pan with a ballpeen hammer if the sump doesn’t clear the steering components or crossmember, Moroso suggests taking pictures of the critical areas and calling the technical department. They may recommend returning the pan for modification.
Finally, is it better to mount the pan at the end of the short-block assembly, or when the intake manifold is bolted down? Savvy engine builders do it as a last step. Who wants to pull the pan because a stray washer or valve-cover bolt fell into the crankcase?
Installing the pan after the top end is all buttoned up isn’t a bad idea!
