If you're looking to upgrade your engine's heart with some serious bearings, let me tell you about these ACL Race Series Engine Bearings. These aren't just any bearings; they’re specifically designed for those of us who push our engines to the limit—think high RPMs and demanding conditions. Whether you've got a 4, 6, or 8-cylinder beast, these bearings are made to handle the heat and stress that comes with performance driving.

So, what makes these bearings stand out? First off, they’ve got a high-strength overlay plate that’s thinner than your average bearing. This isn’t just for looks; it actually helps with fatigue resistance, so you can rev your engine without worrying about the bearings giving out. And let’s talk about the hardened steel backs on the rod bearings. They provide solid support for the lining and help keep everything snug in the housing, which is crucial when you’re pushing for those extra horsepower gains.

Now, if you’re like me, you know that bearing retention is key. These babies come with increased crush, which means they stay put even under pressure. They also ditch the flash plating on the back, which is a game-changer for heat transfer. Better heat management means better performance, and that’s what we’re all about, right?

Another cool feature is the increased eccentricity. This helps counteract bore distortion when you’re hitting those high RPMs, and it aids in forming hydrodynamic oil films. Plus, with 3/4 grooved main bearings, you get optimized load carrying surface area and improved oil flow to the conrod bearings. It’s all about keeping things lubricated and running smoothly.

Consistency is the name of the game, and these bearings have tight wall tolerances to help you maintain those clearances. And if you’re working with a performance crankshaft, the enlarged ID chamfers on the edges are designed to accommodate larger fillet radii, which is a nice touch.

As for specs, these bearings come in standard, .25, and .50mm oversized options. You’ll get an extra +0.001” oil clearance, which can make a difference in performance. The material is tri-metal with hardened steel backs, and they fit standard shaft sizes from 2.0468 in to 2.0472 in. For tunnel sizes, you’re looking at 2.1654 in to 2.1661 in. The max wall at the crown is 0.0589 in, and the overall length is 0.792 in.

For those running a Ford/Cosworth 2.0L (YB), the 4B2166H-.50 set is a solid choice. If you’re serious about getting the most out of your engine, these bearings are worth considering. They’ll help keep your setup reliable and ready to roar.