Main Bearings, .040 Case, .0200 Crank, .080 Thrust

OVERVIEW

When it comes to resurrecting a classic air-cooled engine, precision is the difference between a motor that lasts for decades and one that fails within the first thousand miles. These IAP Silverline Main Bearings are engineered specifically for high-tolerance engine rebuilds where the engine case and crankshaft have undergone significant machining to restore structural integrity. If your magnesium or aluminum case has been line-bored .040 inches over and your crankshaft journals have been ground .020 inches under, this is the exact set you need to achieve the perfect oil clearance. These bearings are steel-backed for superior strength and heat dissipation, ensuring that even under the high temperatures of a summer desert cruise or a spirited run in a heavy-duty dune buggy, your bottom end remains stable and secure.

This particular set is a lifesaver for rare or vintage cases that have seen a lot of miles. The .080-inch thrust cut is a heavy-duty specification designed to accommodate cases where the thrust surface has been significantly worn or damaged and requires a deep cut to return to a flat, square surface. By utilizing these specialized Silverline bearings, you are not just putting an engine together; you are saving a piece of history that might otherwise be destined for the scrap heap. Designed for Type 1, 2, and 3 engines, these bearings provide the tight tolerances required to maintain proper oil pressure, which is the lifeblood of any Volkswagen flat-four. Trust in the quality of steel-backed construction to provide the longevity and reliability that Appletree Automotive customers have come to expect for their Beetle, Ghia, or custom rail projects.

FITMENT

• Volkswagen Type 1: 1961-1977 Beetle and Super Beetle (1200cc, 1300cc, 1500cc, and 1600cc based engines)
• Volkswagen Type 2: 1961-1971 Transporter / Bus (Up to 1600cc Dual Port)
• Volkswagen Type 3: 1961-1973 Fastback, Squareback, and Notchback
• Volkswagen Karmann Ghia: 1961-1974
• Volkswagen Thing (Type 181): 1973-1974
• Custom Applications: All VW-based Dune Buggies, Sand Rails, and Trikes utilizing a Type 1 engine case.

TECHNICAL SPECIFICATIONS

• Brand: Silverline / IAP
• Construction: High-strength Steel-Backed for maximum durability
• Case Bore (Oversize): .040 inches (1.00mm)
• Crankshaft Journal (Undersize): .020 inches (0.50mm)
• Thrust Surface (Oversize): .080 inches (2.00mm)
• Engine Compatibility: 40hp, 1300, 1500, and 1600cc based air-cooled flat-four engines
• Part Number: 111-198-485OS+2
• Weight: Approximately 0.8 lbs
• Manufacturing Location: Mexico

PRO TIPS FROM THE SHOP

Tip 1: Verify Your Machining Dimensions with Micrometers

Never take the machinist''s word as gospel without double-checking the measurements yourself. Before installing these bearings, use a high-quality micrometer to measure your crankshaft journals and a dial bore gauge to check your engine case. You are looking for a .040-inch oversize on the case and a .020-inch undersize on the crank. If these numbers don''t match the bearing specs perfectly, you will either have zero oil pressure or a seized motor. A "dry fit" without the crankshaft is also a great way to ensure the bearings sit flush in the case saddles without any high spots or debris trapped underneath.

Tip 2: Deep Clean the Oil Galleys and Bearing Saddles

When an engine case is machined for a .040 bore and an .080 thrust cut, a massive amount of metal shavings and cutting fluid is introduced into the engine''s internal passages. Simply spraying it with a garden hose isn''t enough. You must remove all oil galley plugs and use specialized brushes to scrub every internal passage. Even a tiny speck of magnesium trapped behind a main bearing can prevent it from seating correctly, leading to a "spun bearing" shortly after startup. Always wipe the back of the bearing and the case saddle with a lint-free cloth and a bit of lacquer thinner to ensure a perfectly clean, dry contact surface before assembly.

Tip 3: Don''t Forget the Assembly Lube and Thrust Surface

Dry starts are the leading cause of premature bearing failure in newly rebuilt VW engines. When installing these .080 thrust bearings, ensure you apply a generous amount of high-pressure assembly lube to the bearing faces and the thrust surface specifically. However, do NOT put assembly lube on the backside of the bearing (the side that touches the case); that surface needs to remain dry to ensure the bearing "bites" into the case and doesn''t rotate. Once the case halves are torqued to spec, ensure the crankshaft spins freely by hand. If there is any binding, stop immediately and investigate the cause before proceeding with the rest of your build.