Manufactured in Mexico by Silverline -an Original Equipment Supplier. Top engine builders will tell you that all aluminum center main bearings can cause increased bearing wear or premature failure and will eventually pound-out the center main web of the engine case due to the bearing’s softer construction. The cure...new Silverline Engine bearings - with STEEL Backing and an Aluminum Face. OEM Quality Main Bearings with STEEL Backing. Available in sizes to fit most case and crank combinations.