- The piston is 87mm, that's 1mm larger as opposed to typical 86mm, and the fabric is lightweight and strong A4032 solid aluminum alloy. The desired clearance of 0.While this isn’t much an engine flaw as much as It's really a design and style flaw, it does have an impact on the RB30ET In the Holden VL Commodore. Due to the design and style on the