Which UZ Is Best?

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Which UZ Engine Is Best?


There’s quite a bit of misinformation out there. The short answer is “it depends what you’re using it for, but in most cases, any 98+ 1UZ, 2UZ, or 3UZ.”


Non-VVTi 89-97 1UZ Features:

  • 6mm thick valve stems. More ideal for high lift cams. Used 33.5mm intake and 28mm exhaust valves

  • 1990-1994.4 had thicker rods, more ideal for boosted applications. Many out there have made 650+rwhp on these rods


98+ 1UZ, 2UZ, and 3UZ Features:

  • 5.5mm valve stems. Lighter valvetrain. 

  • Shim under bucket instead of shim over bucket. Helps contribute to lighter valvetrain.

  • Better, larger intake port design

  • Larger valve faces. All 98+ (1UZ, 2UZ, 3UZ) engines used 34.5mm intake valves and 29mm exhaust valves, which is +1mm larger on both than non-VVTi engines 

  • COP (coil over plug) ignition, ditching the distributor setup (Early non-VVTi UZ ECU and ignitors known to be unreliable)

  • 36-2 tooth trigger wheel for better resolution and more dialed in tuning

  • Variable Valve Timing-intelligence (VVTi), for more torque and better gas mileage

  • No EGR to block off, eliminate, or have issues with

  • Dual stage intake manifold (ACIS). Longer runner design for low end torque, with a vacuum operated butterfly valve switch that shortens the runner length for higher RPM power


It should be noted that:

  • All UZ engines share the same exhaust manifold flange pattern, which is symmetrical. This means any year 1/2/3 manifold will bolt to any other 1/2/3 engine, however the shape/design of manifolds is also different. Not all manifolds fit all chassis’. Some manifolds can be swapped to point the exhaust forward, making a turbo setup easier/cheaper to design

  • All 1UZ and 3UZ engines use aluminum blocks with 6 bolt mains; there are 4 studs in the middle, and 2 bolts from each side of the block. There are no factory oil squirters on any of these engines to the best of my knowledge. 

  • 2UZ engines all use 2 bolt mains, iron block. These did come with oil squirters to cool the pistons for endurance and longevity. Higher HP guys will block these off for increased oiling to everything else that needs it more

  • Gerotor design changed for the 98+ oil pumps. These output more volume, but are otherwise interchangeable. We use upgraded/modified VVTi oil pumps on all engines we build

  • 1UZ VVTi and 3UZ engines are almost completely interchangeable with each other. The main differences between them are the throttle body (3UZ is full electric, the 1UZ VVTi is hybrid cable actuated and ECU controlled), the larger bore diameter on the 3UZ (making it a 4.3 instead of a 4.0), and the coolant port shape is slightly different in the block. Both engines use the same basic casting, and externally, have identical dimensions. 

  • 2UZ used a plastic version of the cam gear covers and intake manifold. These should be interchangeable.

  • 1UZ VVTi and 3UZ heads are the exact same part number, and 100% interchangeable. Connecting rods are 100% the same as well. 

  • Intake manifolds are identical, except for one half having a different bolt pattern for the throttle body, so they are not accidentally interchanged. Exhaust manifolds, mounts, crankshafts, bearings, rods, timing belt, timing accessories, cam covers, cam gear covers, etc. are all interchangeable as well.

  • 1UZ/3UZ and 2UZ block hardware is not interchangeable. Different engine mount locations, and different thread pitch for some hardware