MHP 139 NIGHTMARE Crate Engine. Available with MSO which is equivalent to a title for an engine. 4.500" Bore 4.375" Stroke 172 Horsepower 161 Torque Dyno graph is with a D&D Big Bore and it's a torque MONSTER with 160 foot pounds from roughly 4,000- 5,500 RPMS. With a larger Exhaust setup like our MHP Pro-Mod, Thunder Header or Burns Stainless you'd see some extra HP above 5,500 RPMS