Quote:
Originally Posted by dennis in se pa
I heard it was not viable because of emissions. Looks like a "semi hemi" is. Tks for the correction.
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Sorry to be so picky, but as a former drag racer who really geeks out on this stuff (and a huge MOPAR fanatic), I feel like a quick rundown on combustion chamber and head design might be in order.
Those are true Hemi heads. Both the older one shown and the new one. Ford and Chevy both ran "semi hemi", or "canted valve", or "twisted hemi" designs. Chevy big blocks (396, 427, and 454) and 429 Fords (the 351 Cleveland was similar, in a small block package).
Here is Chevy's version:
Here is Ford's version:
Notice the valves are neither straight across from one another, nor are their stems parallel to one another. Hence the "twisted hemi" moniker.
Here is a typical "wedge" head. This one is a big block MOPAR, but small block Chevs, small block Fords (along with their 427 "FE" series), small block MOPARs, and many other V-8's used this layout. The valves sit next to one another, and their stems are parallel. Easy to manufacture, but really sucks for flow.
