What is the fine-grained topic of the following text: Creator Kar Kraft modified the architecture of 428 Cobra Jet and Super Cobra Jet to make room for the motor and make it a threat in the competition against the infallible 426 Chrysler Hemi. Only return the topic.
Modifications of 428 Cobra Jet and Super Cobra Jet by Creator Kar Kraft for competition against 426 Chrysler Hemi