All DOHC engines have somewhat hemispherical combustion chambers. And the multi valve design is likely an improvement over the Chrysler Hemi.
The DOHC engines also have a spark plug placement in the center of the combustion chamber; a big plus.
The Ford Boss 429 is also a Hemi and I think way back when that there was even a small block Chevy Hemi built.
My 1975 Corolla with the 2T-C engine was a “hemi” all 79 HP of it LOL.
I remember when Chrysler introduced the “hemi” V-8 back in 1951. The engine had a 332 cubic inch displacement and replaced the 322 straight 8 in the 1950 and earlier models. In 1952, a smaller version of the engine was introduced in the Desoto line and the models with this engine were the FireDome models. The Desoto engine had a 276 cubic inch displacement. Dodge introduced the V-8 in 1953. It displaced 241 cubic inches, but I think it had a polyspheric combustion chamber as opposed to a hemispherical chamber.
The fast model of the Chrysler was the Saratoga. It had the hemi V-8 of the New Yorker, but had the shorter Windsor body. Unfortunately, the Chrysler’s performance was hampered by the “lift and clunk” semi-automatic transmissions. This automatic transmission could be had with either a fluid coupling which did not multiply the torque or a torque convertor which did improve acceleration, but with both set-ups, one had to release the accelerator to enable the transmission to shift. On some of the torque convertor equipped transmissions, the engine, torque convertor and transmission shared the same oil which led to problems. I remember the 1953 Dodge dealer recommending that one purchase the GyroMatic with the fluid coupling as opposed to the GyroTorque where the transmission, torque convertor and transmission shared the same oil.
I always thought it was unfortunate that Chrysler didn’t introduce a fully automatic transmission until mid 1953 in its Chrysler line and in 1954 in the Desoto and Dodge lines. The Dodge V-8 in the 1953 Dodge was far superior to the old straight 8 in the Pontiac or the flathead V-8 in the Mercury. However, the switch was on to automatic transmissions and Dodge sales suffered partly for that reason in 1953.
The upscale GM cars, Oldsmobile 98, Buick, and Cadillac all had fully automatic transmissions when the Chrysler hemi came along in 1951. From mid 1949, Fold bought the HydraMatic transmission from GM for installation in its Lincoln cars. Chrysler remained behind the times in the automatic transmission department.
It’s worth noting that Chrysler introduced the “trademark” name Hemi to be applied to it’s motors. GM did similarly with “Northstar” and Toyota does with their " iforce " motors. It IS just a trademark no different then if someone decides to call their motors OHC motors because they have overhead cams, noting that…there are a bunch of others with OHC. Heads have been updated and changed and I would not be surprised if the heads on newer so called Hemis were dramatically different then older ones and perhaps not even true hemi heads. It’s just a name.
I recall rebuilding one of those little Toyota hemis, @pvtP. It was actually very basic mechanically and I’m pretty sure that it was not an expensive job.
I recall rebuilding one of those little Toyota hemis, @pvtP. It was actually very basic mechanically and I'm pretty sure that it was not an expensive job.
It was great for a 1st car, easy to work on, at the time part weren’t that expensive, and was a great learning experience.
I don’t think it ever went into production but many years ago Honda came out with a motorcycle that on the outside was similar to the old CB 750.
On the inside it was vastly different and those 4 cylinders had been replaced by a single, very oblong cylinder filled with a very oblong piston and oblong piston rings. No idea whatever became of that thing but it was stated at the time that if cylinder boring was ever needed the only people that could do it would be Mazda due to their work with rotary engines.
Of course the odds of Mazda taking time out to bore a motorcycle cylinder are about slim and 0.
I recall that oblong piston Honda engine @ok. It seems that Honda wanted to compete with a V-8 engine and had worked out all the details and built a prototype but the AMA saw the possibility that the engine could rule the race tracks and refused to allow an 8 cylinder so Honda built a V-4 with obling pistons just to thumb their nose at the AMA. That was in the late '60s when Harley was taking a real beating as I recall. But my memory and my looks are fading fast. I have no idea where I ran across the story on that engine. It’s been a while.
Honda NR;
Hemi heads flow air, lots of it. That makes horsepower, LOTS of it. The surface area of the hemi head is large, very large. That lets a lot of the heat of combustion leave through the water jackets instead of pushing the piston down as expansion. A small pent-roof 4 valve or 2 valve wedge head is more efficient from a heat transfer point of view and can be made to flow lots of air with the right port design. The hemi head also does not swirl the combustion mixture as well as a wedge design for good combustion.
The Hemi from Chrysler was a ground pounding, high revving brute that deserved all the credit is got in the 60’s. Today it’s marketing.
I don't think it ever went into production but many years ago Honda came out with a motorcycle that on the outside was similar to the old CB 750.
Honda made about 700 NRs at a price of around $60,000 dollars each. That’s one reason most of us will never see one.
Now that the price is mentioned, I remember why those Hondas were never a full-on production line item. Pretty fascinating piece of engineering though.
"Today it’s marketing"
It always was. And yet, many are still fooled into believing the mystique of the name.
That’s the difference between GREAT marketing and just marketing.
With the spark plug at the center of the piston, the flame front only needs to travel the radius of the piston (vs the diameter of the piston when the plug is located over to the side).
With less distance for the flame front to travel, the “yet-to-be-burned” gasses at the end of the piston have less time to rise and detonate (from the rising pressure).
In addition to the previously mentioned hemi advantages, this allows for more optimal spark advance timing without worry for detonation.
I don’t think any one doubts some advantages to this design. But, just like other subtle design differences, they all had their advantages and disadvantages and which a manufacturer chose to use represented their priorities. Like I said, it’s like saying, we use direct injection. Well, so don’t a lot of other makers…
No street designs today are anything near a true ‘hemi’, and that’s good. The angle between the intake and exhaust valve (2 and 2 now) has been continually reduced over the last 20 years to get better efficiency, emissions, and hp. Compact combustion chambers are the rule, unlike the old 426.