08-17-2006, 12:16 AM
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A side note: My 1956 Dodge V8 had an option of using hemi heads on the 271 cu.in engine. I can't find readily what the increase in hp was by swapping the hemi heads.
I did find this...on page 96 of the Dodge C series truck book, " The new 354 Hemi engine was the largest of the Hemi family and it was destined to rule the truck industry through the 1959 model year. Premium features of the new engines included positive exhaust valve rotators, advanced sodium filled exhaust valve stems, stellite faced exhaust valves and exhaust valve seat inserts and chrome plated top piston rings.
Sure sounds to me like Dodge was taking hints from Alfa Romeo as to how to get some "job rated" power from their engines.
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08-17-2006, 02:01 AM
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 Quote:
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Originally Posted by Greg Gordon
Mats, before you knock it, keep in mind the 426 Hemi put out just as much power per cubic inch as a 2.5 or 3.0 Alfa V6, probably more, and it could rev higher! It was a great engine.
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GTV 2000 -77 [URL=http://www.alfapower.nu/gallery/gtv]Pics[/URL] <= These are picture links you know...
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08-17-2006, 06:35 AM
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Quote:
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Originally Posted by MALDI
The new Dodge hemi is DOHC with two plugs per cylinder (sound familiar?)
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I stopped arguing with the kids over at the Charger Forums about head design. They are very sensitive about their "Hemis". Even the Charger owners with the 3.5L DOHC V6 want to call their cars "Hemis". I try to explain that the 3.5L is a Pentroof with 4 valves per cylinder which is a much better design than any two valve could be.
I will say that my 5.7L 2006 Charger is a blast to drive. I missed a very torquey engine and the "small" Hemi has torque to spare (390 Ft Lbs and 350 HP with the Road and Track package). The 6.1L engine has numbers in the 426 range.
Dave
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Last edited by DaveC; 08-18-2006 at 01:18 PM.
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08-17-2006, 09:07 AM
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I had the impression that the topic had already been discussed, and indeed it was in this thread.
As for Alfa, Merosi designed the 1914 GP on Henry's scheme, with two overhead camshafts, four valves per cylinder and dual ignition. But at that time, the issue was reliability, not so much performance.
Henry himself didn't invent the DOHC. I remember having watched at Retromobile a few years ago a huge marine engine, around 1.80 meter high, brass bells around each cylinder as water jackets, and it had DOHC. It was dated 1905 if my memory serves. Can't say the marque. |
08-17-2006, 12:08 PM
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Hemi Now
All this is well and good but the hemi-shaped combustion chamber is not the best shape when it comes to current emission control practices. Too much surface area and no squish zone. I have tried to find if the modern "Hemi" engine is really still a hemi and can find nothing from Dodge one way or the other. Anybody have any information about this?
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08-17-2006, 12:45 PM
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The modern Dodge Hemi is close to a hemi, it's a lot like the Alfa V6.
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08-17-2006, 01:17 PM
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Here is a writeup from Allpar.com with internal pictures.
http://www.allpar.com/mopar/new-mopar-hemi.html
Dave
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08-17-2006, 06:04 PM
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I stand corrected vis-a-vis the pushrods. (I looked at the photos on the same AllPar web page and somehow came away with the impression that it was DOHC!)
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08-18-2006, 11:55 AM
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4 valve, dohc dual ignition hemi in 1914?! that sounds just a little more advanced than the american engines that finally came out with the "ingenious" all-glorious iron blocked, iron head pushrod hemi v-8s in the oh-so early 50's. I mean come on, practically all the European makers were always 20 years ahead in design.
and whether those design features were for reliabilty or performance is beside the point I think, still amazing.
in my opinion
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08-18-2006, 03:39 PM
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Quote:
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Originally Posted by alfadan
4 valve, dohc dual ignition hemi in 1914?! that sounds just a little more advanced than the american engines that finally came out with the "ingenious" all-glorious iron blocked, iron head pushrod hemi v-8s in the oh-so early 50's. I mean come on, practically all the European makers were always 20 years ahead in design.
and whether those design features were for reliabilty or performance is beside the point I think, still amazing.
in my opinion
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08-19-2006, 07:59 AM
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Quote:
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Originally Posted by DaveC
I stopped arguing with the kids over at the Charger Forums about head design. They are very sensitive about their "Hemis". Even the Charger owners with the 3.5L DOHC V6 want to call their cars "Hemis". I try to explain that the 3.5L is a Pentroof with 4 valves per cylinder which is a much better design than any two valve could be.
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Hemi = teh fAstar
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08-19-2006, 11:52 AM
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Quote:
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Originally Posted by dretceterini
Hemi heads date back to before 1910. DOHC dates back to circa 1912. The first ALFA engineer to use hemi heads was in their aircaft department, and was named Roselli. After leaving ALFA, circa 1940 he went on to build a small number of Fiat based sports-racers, using his name. He was also one of the main engineers on the Alfa Bimotore project.
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You already quoted that supposed paternity of “hemi” head by Rosselli and connected it to the Bimotore. I failed to come across such a name in my review of the aeronautical activities of Alfa. I don’t say he didn’t exist, but he is never quoted as having been involved as leader of any aero project. I find the names Bruché, responsible for the first developments on the license-built Bristol Jupiter, and Raimondo Gatti, first involved with a planned double-row radial in 1928, a project dropped, then later technical director of the San Martino plant in Pomigliano. And of course Jano, designer of the D2 radial, and Giustino Cattaneo, from Isotta, who designed the double-row AR 135.
By no way aero activity by Alfa can have led to technological advance in the combustion chamber area: the first hemi, DOHC, 4 valves, twin spark is in a car, the 1914 GP. Before that, the only aero activity is putting a 24HP engine into Franchini’s plane in Sept. 1910. But that’s a “plain” side valves design. And the next aero activities are assembling Isotta “V6” engines in 1918, then building Bristol Jupiter and Pegasus (and derivates) under license from 1926.
OTOH, the Bimotore itself cannot be related, as it used 2.9 or 3.2 8Cs from the current Tipo Bs. And the main responsible for that, er, unconventional project was Luigi Bazzi.
So either you have precise information and you would be kind to share it as to who exactly was Ing. Rosselli and what he did achieve for Alfa, or there’s some confusion somewhere and I fail to understand why you come again with an unsupported attribution of paternity. He may have claimed himself some achievements, but I doubt they actually were what you describe.
As for the “hemi” in se. It seems obvious to me that already around the WWI it was clear that side valves were an outdated design. But pushrods and OHVs, let alone DOHC, were regarded as too expensive for production. Alfa was among the first to sell passengers cars with DOHC from the late 20s (6C1500 Sport and followers), then to mass-produce them from the 50s. The US car industry instead stuck to side valves and overall outdated designs up to the 60-70s. It’s nothing more than a marketing gimmick to promote the “hemi” chamber 50 years after DOHC has been found as a much better design. I feel sorry for those who got caught by such a rough propaganda and seemingly still believe in it today!
Today, as it has been raised above, the hemi design is no longer looked at as the most efficient design: roof-shaped chambers (less surface), with 4 valves (less inclined for the same valve area) and suitable squish zone are more efficient thermically as well as for getting favourable turbulence. Lighter and flatter pistons are another key feature for inertia and heat transfer. But 50-60 years ago, the compression was much lower, and those issues were not as important. The fact progress in GP engine output in the late 30s was mainly related to the use of fuels accepting high supercharging pressures and at the same time able to control the combustion temperatures. The roof shaped heads were recognized from then by the leading designer for such questions, the British Harry Ricardo, who was BTW consulted by Wifredo Ricart for the 162 16-cyl. and 512 flat-12 head designs. The “Heron” type chamber, with a flat head and concave pistons (see Alfasud), while being a newer design, was discarded as less efficient, and Ricardo advised for 4valves.
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08-19-2006, 03:48 PM
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Roselli
First, his name is spelled with one "s". He was an engineer in Alfa's airplane division in the 1920s and 1930s. I do not know what his official title or authority was. He later transfered to Scuderia Ferrari, and HE claimed that the Bimotore was his idea; not Bazzis, and also that that HE was the head engineer on the project. HE claimed that he was the designer of the hemi-head, but obviously it was designed years before him. After he left Alfa, he was involved with the "etceterini" makers Tinarelli and Volpini, and even built a few cars with his name on them. I do know he developed a OHV hemi head for use on FIATS in the 750cc and 1100cc class, and one of these heads was used on a pre-war 1100cc Colli bodied car that raced under the number 39, in the 1940 MM. He also built a Colli bodied car that ran in the Italain 1100cc class, owned by Botazzi and raced under the Scuderia Ambrosiana banner, and a similar looking Colli bodied 750cc car that was raced by Bonetto circa 1947. That's all I know about him....
Stu
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08-20-2006, 12:48 AM
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Quote:
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Originally Posted by Farace
The 426 Hemi was factory rated at 425 HP, but the story going around was that the factory rated it low for insurance purposes and that it actually got closer to 500 HP in stock form.
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yielded 502 HP on Ron Neals German water brake dyno. The HEMI engine was the real deal fellas! I sold the car at auction to a Canadian collector who still has it. It had 32,000 miles on it when sold, and he had added another 1100.
My sale price was $5600 in 1976. Lets not talk about what it's worth today.
Still have my 66 Alfa I bought new in 66 though !
Gordon Raymond
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08-20-2006, 05:51 AM
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Quote:
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Originally Posted by dretceterini
First, his name is spelled with one "s". He was an engineer in Alfa's airplane division in the 1920s and 1930s. I do not know what his official title or authority was. He later transfered to Scuderia Ferrari, and HE claimed that the Bimotore was his idea; not Bazzis, and also that that HE was the head engineer on the project. HE claimed that he was the designer of the hemi-head, but obviously it was designed years before him. After he left Alfa, he was involved with the "etceterini" makers Tinarelli and Volpini, and even built a few cars with his name on them. I do know he developed a OHV hemi head for use on FIATS in the 750cc and 1100cc class, and one of these heads was used on a pre-war 1100cc Colli bodied car that raced under the number 39, in the 1940 MM. He also built a Colli bodied car that ran in the Italain 1100cc class, owned by Botazzi and raced under the Scuderia Ambrosiana banner, and a similar looking Colli bodied 750cc car that was raced by Bonetto circa 1947. That's all I know about him....
Stu
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I have no doubts you gathered those claims from studying his post-Alfa "etceterini" activity. And I guessed right that your statement was based on his own claims. But in such a situation, why do you endorse his obviously self-promoting claims when they are incompatible with the facts, and that has already benn discussed? That's my point, and I realize afterwards that I may have been a bit harsh in my previous post. But if we want to learn something and behave like proper historians, we should give priority to facts and logics rather than to interested claims, isn't it?
I understand that the paternity of the Bimotore is attributed by Enzo Ferrari, who is certainly not the most reliable reporter. We read in Borgeson (p88) that "good authority credits its design to Luigi Bazzi", and it's common knowledge that Bazzi was the head of the technical office in Modena in the 30s. If Roselli did some design work and was not credited for that, it can be. I doubt he was the "real", forgotten responsible... But we never will know the final word on this
So again, whatever he claims having been repsonsible for, his name doesn't appear in the aero activity - started 1926, so way after Alfa itself had used DOHC in the car sector (1914 GP, P1, P2, 6C1500), and built only on license (Bristol and De Havilland) the aero engine, except for the D2 designed by Jano between 1927 and 1931. And in my eyes, it weakens the further claims from Roselli.
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