Why do some pistons have Skirt Notching
Notching the skirt is something CP-Carrillo does primarily to provide clearance for an oil squirter. Most modern engines have oil squirters at the bottom of the cylinder that point up and shoot oil at the pistons to keep them running cooler. At BDC (bottom dead center) the piston may come into contact with that squirter depending on the design. One way is to make the skirts of the piston shorter to avoid it entirely. Sometimes this method is not feasible if the skirt length is already short and shortening further would have adverse effects. In these cases we machine a little notch over where the squirter is located to avoid any clearance issues.
“Stroker” pistons often need modified notches over stock stroke piston notches because the piston goes even further down in the cylinder at BDC and thus gets even closer to the oil squirter. But due to CP-Carrillo’s long relationship and expertise along with many of the top stroker crank manufacturers, we have the bases covered. This is all to limit the amount of any “touch up” machining our customers and/or engine builders may have to do while performing their piston installation.
Other reasons for notching can be for crank counterweight clearancing, or in the case of many Harley Davidsons where the pistons share the rod bottom end and crank journal, to prevent the two pistons from colliding into each other!