Oil Sump Modifications come about for various reasons:-
Some are “chopped to improve the “ground clearance”, others to improve oil capacity, many used in hardcore racing to incorporate a “dry sump” set up, may be to lower the engine in the chassis to improve the “centre of gravity” of the car, particularly important in many race applications.
The following sump modifications were to facilitate fitment of the engine into a “lotus 7″ style kit car. This requires a considerable amount of the sump pan to be removed in order to shorten the overall height of the sump. Don`t forget that if you complete this modification you must also modify the position of the oil pick up position.
Here is the cut down sump pan.
You can see in the image above that a large amount of material has been removed when compared with the standard sump shown below.
The whole lower base has been chopped off to an approx overall depth (from flange face) of 140mm this removes a good few inches from the depth of the standard sump.
Removing such a large chunk of capacity from the sump can effect the cooling, pick up and life of the oil used, so its important that we find some way of reinstating this capacity in the form of a fabricated “wing”, “infill” or a form of additional oil tank. Usually in a case like this our policy is to add additional capacity as and how the customer or specification of the vehicle requires. In the above case of a “Kit Car” we normally add a “wing” to the sump to gain back that lost capacity. In the case in hand we have taken the customers sump and parts he has made himself to tack up and reinstate the sump plus an additional area under the “slope”of the existing sump to gain back some lost oil capacity. Care has to be taken to ensure that if this is done there is not an area for a “dead spot” where oil does not or cannot circulate and become “stagnant” and not part of the main oil amount.
As the vehicle is to be used mainly in a “fast road” application a small amount of internal baffling has been used to reduce the amount of oil “slosh” up the sides of the sump during long hard cornering, where in extreme cases the pick up could be sucking air, not at all good for the life of your engine.
If the vehicle was to be a track day or out and out race car then the arrangement of oil baffle plates would take on a different meaning and design. We have in the past added complete length and width fill baffle plates with integral partitions and “flap” gates that do not allow the oil to flow out of the immediate pick up chamber area, only into it. Like all fluids gravity and “g” forces during racing can have a massive affect on how the fluids move around the contained area they are held in and this needs careful consideration in extreme cases.
Welding cast aluminium can be a little “hit and miss” sometimes as the quality of the casting varies tremendously between makes and models, new and old. Problems may occur from inception of the product dependant on the quality of the casting and various factors during manufacture may affect the final quality of the product, One being oxide removal, aluminium weather molten or solid has an oxide form on the surface (more so when in a molten form), if this is agitated too much in a molten state it can leave “inclusions” within the casting due to the polymorphic (crystallising) nature of the oxide in certain conditions. Various contaminants could be present in the casting dependant on the methods used and these all have an effect on the cast quality and also the “weldability” of the cast item.
Typical problems we come up against when modifying and welding cast aluminium items is:- some castings can be very “hard” and need a considerable amount of heat input to actually improve the welding qualities. This has been the case when we have modified brand new (direct from ford) sumps for the kit car industry. It has been the case in the past that we have heated and allowed to cool in an oven (bless the wife), heated again in an oven then been able to weld the casting much easier, e.g. the weld flows much easier. It has also been the case that we have the dirtiest, oldest oiliest sump possible, cleaned it down and it has welded a treat with no preheating or warming at all.
Due to the nature of alloy castings very often having a certain amount of porosity it can soak up oil and contaminants from the oil, no amount of cleaning can remove these contaminants and its not until you start welding that these contaminants are “drawn” out of the material once molten. Magnesium is often a problem in aluminium castings as sometimes this can concentrate in a small contained area and “flair” as you try to weld over it, this contaminates the welding tungsten causing a black area around the magnesium spot which then has to be cleaned away before further welding can continue.
It is important to remember that if we start to weld the cast when its cold the weld may crack, known as “cold cracking”, as the cast aluminium soaks the heat away so quickly (aluminium has excellent heat transfer capabilities, like copper) it causes the weld to cool too quickly leading to cracking. Dependant on the quality of casting, cracking of the cast can be evident the minute localised heating occurs (as when welding)as the localised heated spot rapidly expands, quicker than the surrounding casting . Hence it is usually a good idea to get a good even heat into the cast sump prior to starting to weld. I have been known to put a clean one in the oven and gently bring the sump up to about 80 degrees before attempting to weld. This method can also work the opposite way where the temperature of the casting can be brought down slowly in an oven.
Once welding is complete it is important to let the Sump cool down slowly. If you cool the sump by filling with water you are very likely to “crack” the sump as the cast material may cool at a different rate to the weld metal.
Leak testing a sump can be a simple affair such as:- any welded areas can be covered in a soft chalk (I use a spray chalk that we also use for Dye Penetrant testing), then filing with gun wash. Should any pinhole or cracks be evident you will see the chalk around the area become damp, highlighting where a defect may be.
I use a full Dye Penetrant test on all welds. This takes the form of cleaning the welded joints, applying a small coating of red dye, leaving for a couple of minutes. Any excess dye is then wiped away and a spray chalk is applied. Once the chalk is applied any defects in the weld (cracks, pin holes, porosity) will become evident as the dye soaks out of the defect as its drawn into the surface chalky coating. This method only highlights surface defects though, should any be detected then we will look closely and complete further tests to see if the fault is all the way through the material or just a surface issue. We may decide to cut out the affected area and re-weld to ensure a leak free job.