This is not simply a piston upgrade. The JUN Auto 1029M-T002 is a complete high-performance 3.2-liter stroker/bottom-end package designed around the Toyota 2JZ-GTE. JUN calls it the Custom Kit EX 3.2L.
🔧 What you get
|
Component |
JUN specification |
|
Engine |
Toyota 2JZ-GTE |
|
Kit |
EX 3.2L |
|
Part number |
1029M-T002 |
|
Bore |
87.0 mm |
|
Stroke |
90.0 mm |
|
Displacement |
3,210 cc |
|
Compression ratio |
8.5:1 |
|
Crankshaft |
Billet, 1003M-T002 |
|
Pistons |
Forged C-Series X6 |
|
Connecting rods |
I-beam X6 |
|
Piston pins |
X6 |
|
Rings |
X6 sets |
|
Snap rings |
X12 |
🧠 Why 3.2L matters
The standard 2JZ-GTE is famous for its 86 × 86 mm bore/stroke configuration. JUN changes the architecture to 87 × 90 mm, giving approximately 3.21 L.
The important change is the 90-mm stroke.
Think of it this way:
2JZ-GTE → JUN 3.2L
86 × 86 mm
↓
87 × 90 mm
↓
3,210 cc
The extra displacement gives the turbo engine more swept volume per revolution, which can improve torque production and response, particularly when paired with an appropriately sized turbo system.
🏗️ The serious part: billet crank
The centerpiece is JUN’s 1003M-T002 billet crankshaft. JUN specifically lists the 2JZ-GTE crank as a billet unit.
That makes this fundamentally different from a conventional “bolt-on” engine modification.
The architecture becomes:
Billet crank → I-beam rods → forged pistons → 3.2L displacement
The result is a purpose-built bottom end rather than simply modifying the factory rotating assembly.
⚙️ Piston engineering
The dedicated piston is specified at:
- 346 g piston weight
- 103 g piston pin
- 32.0 mm compression height
- Concave crown
- 16.7 cc crown volume
- 1.7 cc recess volume
JUN specifies the 8.5:1 compression ratio with a 1.6-mm head gasket as the reference configuration.
That relatively low compression ratio makes sense for the intended turbocharged 2JZ-GTE application, leaving room for a substantial boost-oriented engine calibration.
🚀 What makes it special?
I’d describe the 1029M-T002 as a “2JZ-GTE turned into a serious modern competition-style foundation.”
The hierarchy is roughly:
Factory 2JZ-GTE
↓
Forged pistons / rods
↓
Stroker conversion
↓
JUN 3.2L EX
↓
Large turbo + appropriate fuel system + engine management
↓
High-output 2JZ build
The big advantage isn’t merely the additional 210 cc. It’s the combination of greater displacement + dedicated forged components + billet crankshaft + purpose-designed piston/rod geometry.
🏁 The verdict
Engineering philosophy: ⭐⭐⭐⭐⭐
Bottom-end strength: ⭐⭐⭐⭐⭐
Turbo potential: ⭐⭐⭐⭐⭐
Torque potential: ⭐⭐⭐⭐⭐
Street practicality: ⭐⭐⭐
Cost: ⭐⭐
This is the kind of component set I’d associate with a serious Supra/JZA80, drag, time-attack or high-output 2JZ project, rather than a casual street build.
One important distinction: the kit itself does not determine horsepower. Turbocharger selection, cylinder head, cams, fuel system, ECU calibration, cooling, lubrication and the rest of the engine build determine what the completed engine can safely produce.
JUN’s published specification establishes the 3.2L mechanical foundation, not a guaranteed power figure.
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