TP 230 is a new Holden Cylinder Head developed in conjunction with Torque-power and Yella Terra. Port design and testing was undertaken by Bullet Cylinder Heads. Yella Terra modified there proven -9 casting to accommodate the changes required. The result is the most powerful Holden Head yet. 

The first pair of heads were tested on a 461 cubic inch Big PAW Holden Torque-Power engine and made 650hp @ 6000rpm & 620ftlb @ 3900rpm with the dual plane manifold. With the single plane manifold it made 699hp @ 6000rpm & 650ftlb @ 4800rpm. Both of these test were conducted with a 4150 based carburettor and BP ultimate 98 octane fuel 

The Head is based on the -9 Yella Terra Head with the following added features;

• Fits OEM Block, COME Block or New Torque-power 6 Head bolt Block
• Valve Guide locations moved for better flow
• Large 2.15 inch intake valve and 1.625 inch exhaust
• 230cc intake runner volume
• Flows over 350cfm(4.152 inch bore only)