Reinforced exhaust valves Honda Legend V6 3.5 J35A8

Honda engines covered

The J35A8 is the 3.5 litre Honda J family V6 fitted to the four-wheel drive Legend from 2006 to 2012: 24 valves, one overhead camshaft per head and VTEC variable valve timing.

It has 12 exhaust valves, two per cylinder, original part numbers 14721-RJA-E00 and 14721-PXK-000. In a heavy four-wheel drive saloon they spend long periods under load, in contact with very hot burnt gases.

SUPERTECH reinforced exhaust valves

On a naturally aspirated engine, the metal of an exhaust valve head reaches 760 to 870 °C, and goes past 1,000 °C with forced induction. About 75 % of the heat leaves through the seat and 20 % through the guide. An EV8 family steel holds 550 MPa at 600 °C but only 300 MPa at 800 °C: the head fatigues, distorts and the seat no longer closes properly.

The HEVI-3530-12 is made of Inconel, a nickel-based superalloy that keeps 860 MPa at 730 °C and 554 MPa at 815 °C, about 85 % better than EV8 steel near 800 °C.

Its head is dished and measures 30.0 mm; it is the only size offered for this engine.

Exhaust valve technical specifications

HEVI-3530: 30.0 mm dished head, 5.45 mm stem, 114.2 mm length, Inconel.

Valve fitting

On reassembly, check that the 5.5 mm collets bear properly in the groove of the new valves; the KPR-5.5-7A-ST collets suit the J35.

The 12 exhaust seats are checked and recut for a 30.0 mm head before fitting.

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

Technical guide

Our brand

SUPERTECH Performance, in California, has been developing valves and valvetrain parts for racing for more than thirty years. For the J35 V6 it offers an Inconel exhaust valve with a dished head.

How to choose

Only one version exists for this engine:

When reinforced valves become necessary

• Adding a supercharger or a turbo (Inconel version recommended)
• Camshafts with more lift
• Sustained use under heavy load
• Cylinder head rebuild with burnt or distorted exhaust valves

Vehicle compatibility

OEM part number (exhaust valve): 14721-RJA-E00, 14721-PXK-000

Don't forget the inlet valves

With both J35A8 heads off, it is the right time to replace the inlet valves and the valve stem seals as well.