I’ve gotten many requests for detailed information regarding the Oil Pickup, both OEM and the one we manufacture so I thought I’d post, what I know, for everyone to see. Specifically the questions seemed to be about the factory pickup and how/why it fails. Bear in mind this is information that has been presented to me and I am no scientist.
So on to the factory pickups… They are brazed assemblies (it's kind of like welding, but more like soldering with temperatures much lower than welding ~800 degrees. The braze is the gold stuff you see between the pieces. Before the braze can be applied to the metal pieces you put this stuff called 'flux' on them. The flux makes sure that when the parts are heated up that the braze flows between and sticks to the metal parts properly. When operators, or machines, puts the flux on these parts to get them ready for brazing, the flux must AT LEAST cover the area that needs to be brazed together. So the application of the flux is typically quite extensive and sloppy.
This application of flux and brazing seem to be done properly because I've never seen a braze joint failure. The problem is that the flux SHOULD be cleaned from the parts after the brazing process has been completed. We'll come back to this in a second.
Now the tube, where the failures occur, is a simple thin (~.030") walled seam welded tube. A seam welded tube is basically a long skinny flat piece of metal that gets rolled into a tube and then welded where the edges meet. If you look at some of the pics in my link you'll see a distinct line that runs the length of the tube. That's the weld. Welded tubing has it's downside. While cheap, the weld can be the achilles heal if not done properly. In this situation it's a rough surface (when you look under a microscope), which means it can break or crack easier than if it were smooth, and more brittle than the non-welded area of the tube wall.
OK so back to the braze... When not removed from certain process affected areas, specifically a hardened rough weld, it will get into any micro pock mark or pit when it's applied then heated, and a chemical reaction will occur. The flux reacts with the specific metal condition of the weld (harder and pits, etc..) and will etch into the pits making them deeper... this can also make the metal more brittle too. This is what ends up weakening the structure to the point of cracking. And the fact that it's bolted to the bottom of an engine doesn't help either.
Speaking to vibrations and engines modified with bolt-ons. Engine vibration is not as much a contributing factor as you might initially think for a few reasons. The rotating assemblies are fairly well balanced and harmonically dampened. The oil pickup is submerged in oil, and filled with oil. This dampens the engine vibrations tremendously at the pickup. Some assume the pickup is just swinging around from the engine vibrations, but forget that the pickup is also in oil and full of oil. Now where high frequency vibrations do come from is the oil pump. Typically called ‘high frequency pressure pulsation’, these lower amplitude pulses can have a more pronounced affect because of harmonics that can build in the pickup assembly, possibly where a critical frequency may be being reached at certain RPMs (speed of the oil pump).
So essentially, based on what I have experienced and learned, the OEM oil pickup failures are initiated from a chemical reaction from braze flux on the weld seam and these weakened areas are taken advantage of by oil pump induced high frequency vibrations.