Moparts Tech Archive

Big Block

New Hemi a true Hemi?

I was at a friends shop a few days back, and he showed me an article stating the New Hemi in the ranks of Ma Mopar isn't a "true" Hemi.
The article claimed the combustion chambers aren't completely hemispherical like the old Hemi head design. Anybody had or saw a head off of the original now produced 5.7 motor? Just curious.

The old hemi isn't completely hemisphereical either. The 50's hemi's were closest to a true hemi. The new hemi has 2 small quench pads on the side of the combustion chamber, so its like a slightly oblonged hemi combustion chamber.
It is actually a better chamber than the 426 had due to this.

While old hemi heads were great for generating power, they sucked at putting out good emissions numbers. The new heads use just the very top portion of the hemisphere, so you still get the good plug location, but a lot more quench.

The 426 isn't a perfect hemisphere either although it is closer than the 5.7 hemi. The reason the new "Hemi" isn't a true hemisphere is that a true hemisphere has too much surface area for optimal combustion.

The valves are top and bottom just like the original. Spark plugs are in the middle. This whole "It's not a true HEMI" controversy has been drummed up my the gm and ferd guys trying to belittle the fact that the new HEMI is a well engineered small block. Just like the "old" days when gm and ferd guys said the 426 was overated and unreliable.

it's a new era hemi deal with it

Tech Index