what does HEMI mean?

Discussion of the 5.7L-6.1L-6.4L HEMIs.

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nginman
Posts: 1
Joined: Mon Nov 16, 2009 9:40 am

what does HEMI mean?

Post by nginman » Mon Nov 16, 2009 10:44 am

In your General Hemi Discussion section you correctly define a Hemi as an engine with a hemispherical chamber. You even show it correctly in your engine cutaway. So how does Chrysler have the nerve to call these new "Hemis" a hemi. As a long time fan of the original Hemi engines I don't like seeing these dual plug pent roof engines being called Hemis just to market new products. If Chrysler wanted to make new Hemis then why didn't they make true hemis? I am shocked that there has not been a lot of bad press on this issue. These are NOT HEMI engines.

I will now climb down from my soap box.

392heminut
Posts: 488
Joined: Sat Nov 30, 2002 2:16 pm

Re: what does HEMI mean?

Post by 392heminut » Mon Nov 16, 2009 11:46 am

nginman wrote: So how does Chrysler have the nerve to call these new "Hemis" a hemi. As a long time fan of the original Hemi engines I don't like seeing these dual plug pent roof engines being called Hemis just to market new products.
'Hemi' is a trademarked name, and Chrysler owns the rights, they can do whatever they want with it. Doesn't make it right, but does make it legal. As far as being a pent roof head, I disagree with you on that. A pent roof chamber has two flat surfaces at an angle to each other, usually incorporating two valves in each surface;

Pent-roof
A combustion chamber whose upper surface resembles a shallow peaked roof. Usually used with four valves per cylinder.

The new hemi has a modified hemispherical chamber. i.e. it is a curved chamber with a quench area on either side of the valves. I agree it's not a true 'hemispherical' chamber, but if you want to split hairs, neither is the 426 Hemi. A true hemisphere is 1/2 of a sphere;

hemisphere (plural hemispheres)

1. (geometry) A half-sphere, formed by a plane intersecting the center of a sphere.



The 426 Hemi chambers are nowhere close to being 1/2 of a sphere, and neither are the early hemis (although they are closer to it than the 426 Hemis).

No matter what you call it though, the new hemi's combustion chamber is a very efficient design!

As an aside, Harley Davidson's OHV V-twin engines used a hemispherical combustion chamber that was basically identical to the 426 Hemi until the early 80's. At that time they came out with the 'Evolution' V-twin engine that had a combustion chamber that is almost identical to the combustion chamber in the 'new' hemi. Funny thing is, Chrysler was touting the 5.7 Hemi as new technology when they came out with it, and Harley Davidson had already been using the same basic design for 20 years! :o
Owner of the Poor Man's Hemi Cuda

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