The L33 is an all aluminum (with cast iron cylinder liners) 5.3L (325cc), Gen III small block engine that was used in Chevy and GM trucks between 2005 and 2007. It was also known as the “Vortec 5300 H.O.” In stock form it put out a respectable 310 HP and 335 ft/lbs of torque.

They’re available on eBay and Craig’s list for a thousand bucks and can be a fun motor to build. They came stock with a very conservative cam (193 degree duration at .050 on the intake). A cam from an LS3 (bumps to 204 degrees at .050) is a drop in upgrade that’s good for another 50 HP so in a lighter car with some tall gears this can be a great engine while retaining the drivability of a modern era V8. An LS9 cam (211 degrees at .050) would be a real increase (75+ HP) but would need new springs. Either cam would require new lifters, timing set (with a LS2 chain damper) as new thick-wall pushrods but cam swaps to larger size/longer duration typically require a few additional upgrades.

From the rear of the engine, it’s all the same and will accept all popular bell housing/automatic transmission options.

Would love to see a build thread if you're thinking about one.

Best,
Glenn