Hemi?

what exactly is so special about a hemi?

the new one or the old one?

i think he means in general

in general, they're just pushrod V8's that tend to be more powerful than comparable pushrod V8's. The only thing the old Hemi and new Hemi have in common is that they're both pushrod gasoline V8's.

what exactly is so special about a hemi?

They make more HP per CI than wedge motors of whatever brand. They love boost. The more, the merrier. The hemispherical head is especially conducive to running nitromethane. That's why all top fuel and funny cars run Hemi-headed engines.

The 426 Hemi was a purpose built race motor stuffed into small and intermediate sized sedans.

The opposed valves allow for larger valves. The valve angle allows for better port design and higher flow numbers. The valves aren't shrouded by the cylinder walls. All of these add up to more airflow which equals more power. DOHC and some SOHC heads use the same advantages, but Chrysler owns the trademark to "hemi".