The technological advancement of performance engines and even more so from tuned engines will increase the burden of stress on the head gasket. Under extreme conditions of high cylinder pressures and competition use, the head gasket is often the weakest point. The expansion and 3D pressure image shown, displays the effectiveness of the TOMEI multiple layered head gasket with the super grommet design (shown with the pressure image analysis ystem). The sealing performance is pursued with cross-section measurements and utilizing various functions within the design.
Super Grommet Design
Although the stock product is not metal, yet the sealing performance is limited due to the grommet type design. The sealing performance has been improved considerably with the super grommet, to suit these engines and has been proven to deliver excellent reliability. (Super Grommet = Dual Seal Method combining both the Bead Structure & Metal Grommet designs).
Specific Rib Designs
The gas sealing characteristics will improve with the raised rib, but the sealing characteristics of the neighbouring water and oil channels are equally reduced. Therefore when pushing for power gains, these areas are weak points that can allow leakages. The TOMEI design focuses on all areas to provide the maximum seal with the use of the super grommet design. By using the rib height to ensure an equal overall high surface pr ssure seal, where it's needed the most.
EJ257 GRF, GVF
EJ255 06-07 WRX, 08+ WRX
EJ257 04-07 WRX STI, 08+ WRX STI