Effective for the 2008 series, WSB rules will permit twins displacing up to 1,200 cc. Twins will start out with a six kilo weight handicap (168 kg vs. 162 kg for the four-cylinder machines). The twins will also run air restrictors.
Otherwise, twins may be tuned to the same extent as other machines in 2008, with the sole exception being connecting rods. Twins must use stock connecting rods.
To read the entire press release regarding the 2008 rule changes, follow this link