a motor my proffeser refered to as a fordhemi

[Bob In Ct]

The hemi head engine has 2 big advantages over a wedge head engine. The first is it breaths better, the second is the fuel burn (flame progression) is even through the whole power stroke. When the plug is off to the side, some power is lost due to uneven burn.

Bob

[Power Surge]

A couple other things that you can look into that would add some good quality to your paper...

While Dodge is using the HEMI name on these new motors, my understanding is that they are not actually hemispherical chambers. I am not sure on that, just what I heard. Might be worth looking into.

Also, Ford's 4.6 DOHC (DUAL overhead cam) motor is a hemi. It's a modern version, with 4 vales per cylinder, and a central plug. You could use that for your paper to tie old technology vs new.

And one last Hemi fact.... Dodge built ONE 4 valve per chamber 426 Hemi in the 60s. This motor was Dodge's answer to the Ford 427 SOHC. You may still be able to find info on it. I remember a magazine article from the late 80s (I think) about it, titled "the hemi that never was".

Hope this helps.

[Full Throttle Al]

As stated above, spark plug location has nothing to do with a motor being a hemi or not. In the above referenced SAE technical paper, page 12 under Combustion Chamber Design it states "The optimum location for equidistant flame travel is the geometric center..." Obviously, the centrally located camshaft prevents this location from being used. Interestingly, the "First Series" motors had the spark plug on the opposite side of the head, but testing of flow caused it to be relocated to the final location in the "Second Series" of SOHC engines.

Clearly, so that the motor can develop its full potential and the spark plug location design flaw that is inherent with the Single Overhead Cam design be corrected, the answer is a Cammer head that has Dual Overhead Cams!!!

At the same time, a gear drive can replace the chain, here is a one of a kind system built for a cammer motor going in a boat:

[767Jockey]

Just curious - is the block for a SOHC the same block as a normal 427FE? Does anyone currently make SOHC heads new? I guess the question here is, can you actually build one of these engines new now, or do you need to go around rounding up rare old parts?

[olddog]

Originally Posted by Power Surge

Also, Ford's 4.6 DOHC (DUAL overhead cam) motor is a hemi. It's a modern version, with 4 vales per cylinder, and a central plug. You could use that for your paper to tie old technology vs new.

Although the 4.6 DOHC reminds you of a hemi, it is not. I believe the technical term is PENTROOF, but I would have to pull a book to be certain. A hemi head is shaped like a ball (top half) except where the valves are flat. That is to say there are no flat surfaces on a hemi head. The 4.6 DOHC has all flat surfaces (except the curve to match the cylinder wall). The valves are not nearly as canted as a hemi either. However the flow is excellent, and from an emissions/performance point of view it is superior to the hemi in many ways.

[Excaliber]

Superior to the Hemi? Impossible! And nothing is faster than a Cobra, NOTHING!

...got that straightened out.

[Woodz428]

Originally Posted by olddog

Although the 4.6 DOHC reminds you of a hemi, it is not. I believe the technical term is PENTROOF,

I think that you are correct. Pentroof is probably what the 4 valve Mod motor is, as were the DOHC indy engines and literally every new sportbike engine.