Reinforced exhaust valves Toyota 1JZ-GE 1JZ-GTE

Toyota engines covered

The 1JZ is Toyota's 2.5 litre, 24-valve, twin-cam straight six: the naturally aspirated 1JZ-GE, and the 1JZ-GTE with twin turbos and later a single turbo. It powers the Chaser, Cresta, Mark II, Crown, Soarer, Verossa and the JZA70 Supra.

This engine has 12 exhaust valves, original part number 13715-46020 on the 1JZ-GE and 13715-88400 on the 1JZ-GTE. On the turbo version, they handle much hotter gases than on the naturally aspirated one.

SUPERTECH reinforced exhaust valves

The metal of an exhaust valve head sits between 760 and 870 °C on a naturally aspirated engine and passes 1,000 °C with forced induction. The seat removes about 75 % of the heat, the guide about 20 %. An EV8 family steel keeps 550 MPa at 600 °C, but only 300 MPa at 800 °C: the head fatigues, distorts and loses its seal.

Both SUPERTECH part numbers are made of Inconel, a nickel-based superalloy holding 860 MPa at 730 °C and 554 MPa at 815 °C, roughly 85 % better than EV8 steel around 800 °C: a suitable choice for a 1JZ-GTE with raised boost.

The TEVI-1009-12 only enlarges the head, from 30 to 31 mm: burnt gases leave the cylinder faster, to the benefit of filling. The exhaust seats are then machined to this size.

Exhaust valve technical specifications

TEVI-1008: 30 mm head, TEVI-1009: 31 mm head (+1 mm); 5.97 mm stem, 98.1 mm length, Inconel.

Valve fitting

When refitting, check that the collets sit properly in the stem groove; KPR-6T-ST collets suit these valves.

With the TEVI-1009-12, the 12 exhaust seats are machined for a 31 mm head; with the TEVI-1008-12, they are simply reground.

Fit all 12 valves from the same set and replace the exhaust valve stem seals at the same time.

Technical guide

Our brand

SUPERTECH Performance, in California, has been developing racing valves and valvetrain parts for more than thirty years. For the 1JZ, it offers an Inconel exhaust valve in standard size and +1 mm.

How to choose

The choice is made on the size:

When reinforced valves become necessary

• Raised boost or single turbo conversion
• Higher lift camshafts
• Drift, track or drag racing
• Cylinder head rebuild with burnt exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 13715-46020 (1JZ-GE), 13715-88400 (1JZ-GTE)

Don't forget the inlet valves

With the 1JZ cylinder head off, replace the inlet valves and the valve stem seals too.