High Performance Animal / 206 Ported Cylinder Heads Machined For More CompressionHigh Performance, Animal 206 Ported, High compression, Cylinder heads Installing a 1. 250 intake valve or bigger in a stock Briggs Animal or 206 cylinder head provides little to no improvement in performance! Heres why: When installing a bigger valve the side of the valve closest to the combustion chamber wall is so close that it actually restricts the flow of the intake charge. When the vacuum in the cylinder is available to the intake port the