Trojan Boat Forum

"Hemi" originally referred to the shape of the combustion chamber: hemispherical. This is the most efficient shape, with the spark plug in the center and the valves arranged more centrally, for the most efficient/powerful flame propagation. Since the spark plugs must be in the middle and the valve arrangement is difficult as well, these engine are more expensive.

Chrysler began making the powerful hemispherical head big blocks, still used in racing, starting back in the 50's. Chrysler coined the name "Hemi" and some Hemi cars (Cudas, Charger, Chalenger, etc.) have become extremely rare and valuable. It competed with their more traditional wedge engine, again referring tot the shape of the combustion chamber, which had the spark plugs and vales offset.

Chrysler licensed the name "Hemi" and uses it today as a marketing gimmick today on their non-hemispeherical head engines.

rossjo wrote:"Hemi" originally referred to the shape of the combustion chamber: hemispherical. This is the most efficient shape, with the spark plug in the center and the valves arranged more centrally, for the most efficient/powerful flame propagation. Since the spark plugs must be in the middle and the valve arrangement is difficult as well, these engine are more expensive.

Chrysler began making the powerful hemispherical head big blocks, still used in racing, starting back in the 50's. Chrysler coined the name "Hemi" and some Hemi cars (Cudas, Charger, Chalenger, etc.) have become extremely rare and valuable. It competed with their more traditional wedge engine, again referring tot the shape of the combustion chamber, which had the spark plugs and vales offset.

Chrysler licensed the name "Hemi" and uses it today as a marketing gimmick today on their non-hemispeherical head engines.

thank you for clearing that up. i could have probably googled it, but hey, i thought i'd show my total lack of knowledge. thanks for not laughing at me for not knowing what it stood for. much appreciated.
aaron

Ross , How is the New hemi not a hemi ? Yes the are some modifications to it to improve emissions .and making it more efficient .

I have look all over the net and I have yet to see anything agreeing with your statment.

prowlersfish wrote:Ross , How is the New hemi not a hemi ? Yes the are some modifications to it to improve emissions .and making it more efficient .

I have look all over the net and I have yet to see anything agreeing with your statment.

They are hemispherical.

I haven't seen a Dodge Neon with the HEMI logos on it yet...maybe the marketing department hasn't gotten that far down the chain of models?

basically.. design. .The hemispherical combustion chambers create better thermal and volumetric efficiency. Thus, the engine can create more power without increasing compression. Valve placement improves efficency, too.

What happened on the hemis you were looking at ? Did you ever get any photos ?

The difference is the hemispherical design of the cylinder heads.

A 426 HEMI engine, as well as any B or RB Chrysler engine will have the distributor in the front of the engine, regardless of whether it is an industrial, marine or automotive engine.

All other engines, save the slant six or the flathead engines, will have the distributor mounted to the rear of the engine. This includes 331, 354 and 392 Chrysler HEMI engines, regardless - again - of usage. Same applies to Dodge and DeSoto engines of the fifties. The 426 HEMI made its public advent in late 1963, put in race cars in 1964, then as a street package in 1965.

Stripermann2 wrote:

prowlersfish wrote:Ross , How is the New hemi not a hemi ? Yes the are some modifications to it to improve emissions .and making it more efficient .

I have look all over the net and I have yet to see anything agreeing with your statment.

They are hemispherical.

I haven't seen a Dodge Neon with the HEMI logos on it yet...maybe the marketing department hasn't gotten that far down the chain of models?

I didn't say they weren't Hemi's. Indeed they are - as that is the copyrighted name that Chrysler (Daimler Benz) has given them.

I said they don't have hemispherical heads .... because they don't.

The combustion chamber is actually pear shaped (cut in half length-wise), flattened out a bit, 2 large "divots" where the spark plugs are located and "squish pads" at the front and back: which is clearly not hemispherical.

The valve arrangement is similar (but there are now 2 spark plugs and flat-top pistons versus dome-tops) to Chrysler's 50's and 60's hemi engines, which is interesting, but irrelevant to the fact the engine's combustion chamber shape is not hemispherical.

Chrysler 50's and 60's Hemi hemispherical head (no divots around spark plug - just a smooth, hemi-spherical shape to the entire combustion chamber):


Note how the chamber is wider near the larger intake valve than around the smaller exhaust valve on the current (2011) Chrysler 5.7 Hemi head, and the huge divots in the combustion chamber walls around the spark plugs, and the 2 "squish pads" on each side of the chamber:


.... can't imagine D-Benz putting a heavy V8 Hemi in a Neon ... but who knows? Maybe they'll call their little engines Hemi too?

IMO no big deal chrysler hemi is just another engine, the design happens to work well with blowers in dragracing. Other normally aspireated engines are as good or better. Nascar doe snot use them.

However the motors in pics were pretty.

BTW d-benz is long gone its Fiat

Along with the frigging us gov't, unions, fiat and a bunch of other private equity firms

prowlersfish wrote:BTW d-benz is long gone its Fiat

BTW ... D-Benz was the owner who began using the name "Hemi" for their new non-hemispherical-head V8 engines.

Chrysler Marine did build a 426 Hemi.

I just bought book of every Chrysler Marine Service Bulletin from 1964 to 1971 and dated 11-20-65 is a eighteen page spec sheet on the marine 426 hemi.
525 HP @ 6400 RPMs
490 Ft/lbs 4000 RPMs
left hand rotation only
12.5:1 Compression ratio
Twin Holley 4bbl carbs on cross ram intake
copper monel tubular/jacketed exhaust headers
72 C velvet drive

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