ROSS RACING FORGED PISTONS FOR AU 4.0L SOHC USING BA RODS (22MM GUDGEON PIN) These are a custom piston made by Ross for Spool Imports. Pistons are available in: Compression Ratio: 8.5:1 Bore Size: 1.0mm 0.200″ (5mm) Tool steel 52100 gudgeon pins Pistons come with rings, gudgeon pins and pin locks Forged 2618 Rated at 1000HP by Ross Racing ROSS RACING PISTONS: All ROSS Racing Pistons (since 1985) have been forged from 2618 billet bar stock and have been heat treated and aged to a T61 condition (2618-T61). 2618-T61 is the material that is used when fatigue resistance and durability are of prime importance by all premium racing piston manufacturers. This material has less than 1% silicon particulate content. High silicon content pistons (forged from 4032 or MS75) will not stand up to the most extreme stress placed on many racing pistons. If a crack starts to form in a high silicon piston it will continue until the piston experiences a catastrophic failure. Simply stated, adding sand to the aluminum only makes it more brittle. In the rare instance of a 2618-T61 piston cracking, the crack will continue to an area where the stress is not as great and will then stop. Another advantage of 2618-T61 over the high silicon pistons is the ability to keep its shape under extreme pressure and high RPM’s. “Skirt Shrinking” is not a problem with ROSS Racing Pistons.
