43 replies to this topic

[dretceterini]

I know that there were twin OHC cars as early as the teens (both pushrod activated and "true" OHCs), but what was the first one to have domed (hemi) pistons and combustion chambers?

Thanks for you help..


Stu

[rdrcr]

Compiled from one of my HEMI sites:

... Chrysler didn't, and never claimed too. But Zora Arkus-Duntov (Ardun Heads for Fords) didn't either, and I don't believe he ever claimed to.

In The Grand Prix Car Volume 1 by Lawrence Pomeroy, the first mention of angled valves and overhead camshafts is in his description of the 1912 3 liter Peugeot Grand Prix car, designed by a Frenchman named Henri. This was not a hemispherical chamber, it had four valves in what's known as a pent-roof chamber. So it's a level above the hemi. Hence, the inventor of the hemi, if he exists, came up with a way to reduce the potential of the overhead cam, multiple valve design.

Numerous other makes copied Peugeot and by the 1920s angled valves in crossflow heads were the norm in racing engines, both in Europe and the U.S. Delage, Ballot, Bugatti, Chevrolet, Deusenberg, Frontenac, and Miller, to name just a few, were all either hemis or had pent-roof chambers with four valves per cylinder. More recent marques include Jaguar, Aston-Martin, Coventry-Climax, Coswoth, Ferrari, and Maserati.

The major difference between makes is the means of running the valve train; dual overhead camshafts, a single overhead camshaft, or pushrods. Chrysler chose pushrods and they worked amazingly well. By the way, does anyone know what the original hemis were called by Chrysler? "The Double Rocker." It wasn't til the 426 that "Hemi" became standard. And HEMI is now a registered trademark of DaimlerChrysler.

Chrysler never claimed to have the first mass-produced hemi either. I don't know who was first, but BMW had their 2 liter inline 6 cylinder engine in the 328 sports roadster in the mid 1930s. This engine had an in-block camshaft with 18 pushrods, 18 rockers and two rocker shafts. The extra pushrods were horizontal, crossing the cylinder head to operate the exhaust valves. Despite this Rube Goldberg setup, the engine was a good one for its time. It was manufactured under license by Bristol in the UK.

Anyone who has visited the Walter P. Chrysler Museum in Auburn Hills, MI has seen the first Chrysler Hemi, in the form of the XIV-2220 inverted V-16 aircraft engine developed by Chrysler during World War II. The engineers who worked on the project gained valuable experience which they later applied to further experiments with hemi heads on corporate 6 cylinder engines.

I imagine more than one was aware of the existence of the Ardun heads for Ford engines. If there were features which applied to the new engine design, I hope they adapted them. This work lead to the 1951 Firepower V-8 of 331 cu.in. displacement. And to the 1952 Desoto Firedome V-8 of 276 cid. And then to the 1954 Dodge Ram V-8 of 244 cid; all were hemis.

What Chrysler could claim as a record would be the mass production of more hemi-type engines than anyone.

From Bill Watson:

I did a little bit of research and the earliest "hemi" I can find is the 1903 Welch, built by Chelsea Mfg. Co., Chelsea, Michigan. It had a 20-hp, two-cylinder engine with overhead valves and hemispherical combustion chambers. The company moved to Pontiac, Michigan in 1904 and began producing larger cars with 36-hp four cylinder engines, still with overhead valves and hemi-heads. The 1906 engine had a 4.5" stroke and 5" bore with a single overhead camshaft and had one of the first water pumps driven by the fan belt.

The 1906 model also had an adjustable steering column permitting the driver to move the steering wheel up or down the column as needed. In addition to the four cylinder engine, Welch also built a 75hp six-cylinder engine with overhead valves, hemi-heads and a single overhead camshaft.

In 1909 the company was acquired by General Motors Company and set up a plant in Detroit to build the Welch-Detroit, with A.B.C. Hardy as General Manager. In 1911 the powers that be at G.M.ordered the machinery from the Welch plants in Pontiac and Detroit moved to the Rainier Motor Car Co. plant in Saginaw, Michigan. The Rainier Motor Car Co. was formed in 1905 and acquired by General Motors in 1909 or 1910.

Regarding the Ardun Heads:

The basic story is that the head was designed by Zora Arkus-Duntov, later a major force behind the Corvette. In the mid-1940s, he was working under contract with Ford to design an overhead valve conversion for flathead truck conversions; the heads were Hemis with two rows of rockers and plugs going through the rocker covers. They were offered by Ford to truck owners and by Ardun as racing hop-up kits. Some say (or impugn) that Chrysler borrowed from this design when setting up their first test mules.

Anthony Young in his book Hemi: History of the Chrysler Hemi V-8 Engine, interviewed surviving factory engineers and draftsmen about the origins of the design. The word "Ardun" appears nowhere in this book, but company engineers had long had a hemi design in mind, and by 1947 one of them (Moeller) was in the Engine Development Laboratory where, he says "We tested every engine in site (sic)". The company needed a major new engine for their postwar program, and knew of the OHV V-8 R&D at General Motors which became the '49 Olds and Cad units.

Moeller says the lab procured an English production car engine, a Healey with a long stroke hemi design, but high powered and very efficient. They were impressed with this. Subsequently a six-cylinder prototype Chrysler hemi was built, first with chain-driven DOHC, then a pushrod OHV rocker arm version (shown in the book). The latter was successful on road testing, and 'By 1948, Chrysler had a 330ci Hemi-head V-8 undergoing testing...' After successful testing the next version, the 331, was approved for production."

[D-Type]

Originally posted by rdrcr
Compiled from one of my HEMI sites:

... Moeller says the lab procured an English production car engine, a Healey with a long stroke hemi design, but high powered and very efficient. They were impressed with this. ....

I think that would have been the Riley engine in the Silverstone Healey.

Which begs the question "When did Riley introduce their hemi head?"

[rdrcr]

I don't know if this was the first one they built, however, Riley had a two-seater sportscar in 1932 called the Gamecock. It was powered by its immortal Nine engine, a 1.1-liter, four-cylinder engine that used twin camshafts set high in the block to actuate inclined valves in a hemi head via short pushrods and rockers. (Nine stands for nine horsepower, according to an arcane taxation formula of the day. The engine actually made around 34 horsepower in stock form, and nearly 100 when tuned and running alcohol fuel.)

[dretceterini]

I have found a reference to Roselli who was an Alfa aircraft engineer and was involved in the creatiobn of the Alfa Bimotore designing a dohc cross flow, pushrod driven dohc head in 1930, but I am sure there are earlier hemi heads.

[GIGLEUX]

I am one of those who believe the first hemispherical combustion chamber first appear with Pipe (of Brussels) as soon as 1904.

[dretceterini]

Based on what I have found, I would tend to agree.

It seems many of the early dohc motors, no matter if they were pushrod or actual dohcs had a pent roof combustion chamber, which would be more effective....so I don't really understand the development of the round "hemi" combustion chamber design after circa 1915...

[rdrcr]

So, you guys still don't like the Welch Automobiles theory? The design was originally conceived in 1901 and went into production in 1903.

If true, would pre-date Pipe by at least one year.

[VAR1016]

Originally posted by dretceterini
Based on what I have found, I would tend to agree.

It seems many of the early dohc motors, no matter if they were pushrod or actual dohcs had a pent roof combustion chamber, which would be more effective....so I don't really understand the development of the round "hemi" combustion chamber design after circa 1915...

A number of factors here to consider.

I suspect that Ernest Henry, and before him the designers at FIAT (cf 1907 GP car) could appreciate the advantage of a four-valve head. However what they had to deal with was the unreliability of the valaves themselves probably for metallurgical reasons. double the number of valves and in a 700-mile race you are likely to have more failures.

In addition, the large valve area obtained could not be exploited because the early engines could not turn above 4000 rpm (by "early" I mean pre-1915). I doubt at that time that combustion processes were understood so since the hemispherical head in a small bore engine ( because of the long strokes then fashionable) allows for decent sized valves (2 only) this is what Bertarione did at FIAT in 1922 at the beginning of the very successfull 2-litre Grand Prix formula that ran until the end of 1925. The early cars made 92BHP at only 4000rpm on a 7:1 compression ratio with a single updraught carburettor - outstanding - which made them very successful and by 1923 146 HP were being obtained (at 5500 rpm) using a supercharger of which FIAT were also pioneers. These cars could do about 140 mph so it is not surprising that the FIAT formula of two valves at a wide angle were naturally considered to be a Very Good Thing.

The 2-litre V-12 Delage was the ultimate in this period making nearly 200BHP again with similar head design and awesome mechanical complexity.

Regarding production engines, Riley introduced the "Nine" engine at the Olympia show in 1926. This design, developed by Hugh Rose was used by Riley until its identity sank in the morass of BMC in the 1950s.

PdeRL

[dretceterini]

Originally posted by rdrcr

So, you guys still don't like the Welch Automobiles theory? The design was originally conceived in 1901 and went into production in 1903.

If true, would pre-date Pipe by at least one year.

Certainly possible, but I know somewhat more about Pipe than Welch

[Ray Bell]

Would Chrysler really have made more 'hemis' than Peugeot did through their 203, 403, 404, 504 and part of the 505 runs?

I was reading Richard's long post and wondering where mention of Riley (especially since the Healey was mentioned, fitted with a Riley!) and Peugeot might come in.

The 203s had a part-spherical combustion chamber (not a full hemisphere... very few do that!) from 1948 and this was a trademark of the pushrod engines of the marque until they swung over to ohc designs that were close but not quite the same, having a quench area in the chambers. I think the pushrod engines are still in production in either Africa or Argentina, or maybe they've just stopped making them, so there must have been an awful lot made to compete with Chrysler's tally!

What I'd really like to know about, though, is this repeated mention of Chrysler's 'corporate' six with hemi chambers... surely that wasn't put into production?

[McGuire]

Originally posted by GIGLEUX
I am one of those who believe the first hemispherical combustion chamber first appear with Pipe (of Brussels) as soon as 1904.

The Pipe reportedly did not appear in the flesh until the 1904 Paris Auto Show at the earliest. Thus it apparently came after the Welch, as well as George A. Weidley's Premiers in all likelihood. Perhaps we can chalk up this frequently referenced "first" to the continental perspective.

And in any case, I am not sure the hemispherical combustion chamber qualifies as a bona fide innovation. That is, the concept seems too obvious to have an an "inventor" in my view. Its theoretical benefits were understood for decades before any of these engines appeared; however, there were a host of far more pressing issues to be worked out first. Meanwhile, before 1915 or so any advantages to the hemispherical chamber itself were probably no more than theoretical anyway. These early engines were extremely limited in their volumetric effiency, MEP and operating speed.

Quoting from a pamphlet published in Paris in 1862 by M. Alph. Beau de Rochas, stating four necessary goals for an effective IC piston engine: (An excerpt is included in The Gas and Oil Engine by Dugald Clerk, 1886, sixth edition, p. 18)

1. The greatest possible cylinder volume with the least possible cooling surface.

2. The greatest possible rapidity of expansion.

3. The greatest possible expansion; and

4. The greatest possible compression at the commencement of the expansion.

In reference to point one, boldfaced above for emphasis: it is a fact of geometry too obvious to state that the shape with the lowest surface-to-voume ratio is a sphere, or a section of one.

[McGuire]

Originally posted by rdrcr
Regarding the Ardun Heads:

The basic story is that the head was designed by Zora Arkus-Duntov, later a major force behind the Corvette. In the mid-1940s, he was working under contract with Ford to design an overhead valve conversion for flathead truck conversions; the heads were Hemis with two rows of rockers and plugs going through the rocker covers. They were offered by Ford to truck owners and by Ardun as racing hop-up kits. Some say (or impugn) that Chrysler borrowed from this design when setting up their first test mules.

...and of course, it has been suggested more than once that Duntov, in turn, "borrowed" the pushrod-hemi configuration from Talbot.

This is the first time I have seen it suggested that Ford Motor Co was connected or involved with Ardun in any way. Do you know of any primary sources which confirm this?

[dretceterini]

Originally posted by McGuire


The Pipe reportedly did not appear in the flesh until the 1904 Paris Auto Show at the earliest. Thus it apparently came after the Welch, as well as George A. Weidley's Premiers in all likelihood. Perhaps we can chalk up this frequently referenced "first" to the continental perspective.

And in any case, I am not sure the hemispherical combustion chamber qualifies as a bona fide innovation. That is, the concept seems too obvious to have an an "inventor" in my view. Its theoretical benefits were understood for decades before any of these engines appeared; however, there were a host of far more pressing issues to be worked out first. Meanwhile, before 1915 or so any advantages to the hemispherical chamber itself were probably no more than theoretical anyway. These early engines were extremely limited in their volumetric effiency, MEP and operating speed.

Quoting from a pamphlet published in Paris in 1862 by M. Alph. Beau de Rochas, stating four necessary goals for an effective IC piston engine: (An excerpt is included in The Gas and Oil Engine by Dugald Clerk, 1886, sixth edition, p. 18)

1. The greatest possible cylinder volume with the least possible cooling surface.

2. The greatest possible rapidity of expansion.

3. The greatest possible expansion; and

4. The greatest possible compression at the commencement of the expansion.

In reference to point one, boldfaced above for emphasis: it is a fact of geometry too obvious to state that the shape with the lowest surface-to-volume ratio is a sphere, or a section of one.

I don't quite understand what the shape of the combustion chamber has to do with cylinder volume. Isn't a pent roof combustion chamber design more efficient than a hemi shaped combustion chamber?? If it wasn't, why wouldn't even 4 or 5 valve combution chambers be more hemispherical than they are today??

[VAR1016]

Originally posted by dretceterini



I don't quite understand what the shape of the combustion chamber has to do with cylinder volume. Isn't a pent roof combustion chamber design more efficient than a hemi shaped combustion chamber?? If it wasn't, why wouldn't even 4 or 5 valve combution chambers be more hemispherical than they are today??

The answer to this one is the compression ratio.

Whilst the hemisphere might be good in terms of surface area; in terms of volume it is far from good if a high C.R. is to be obtained. It also has to do with valve angles; modern heads use valve included angles as low as 23 degrees - perhaps less. this would be impossible with a hemisphere unless of course one had very tiny valves.

Finally there is the matter of squish/quench. The hemisphere is not strong in these areas.

PdeRL

[dretceterini]

Thanks! That totally agrees with my thoughts...

Stu

[McGuire]

Originally posted by dretceterini



I don't quite understand what the shape of the combustion chamber has to do with cylinder volume. Isn't a pent roof combustion chamber design more efficient than a hemi shaped combustion chamber?? If it wasn't, why wouldn't even 4 or 5 valve combution chambers be more hemispherical than they are today??

Depends what kind of efficiency, so let's distinguish the several kinds at work here. (But first we begin by noting than when we examine the chamber in three dimensions, four valves in two planes essentially impose a pentroof chamber, while two laterally opposed valves deployed in two planes virtually dicate the classic "hemi" layout, irrespective of included valve angle.)

1. Thermal efficiency: The hemispherical combustion chamber is, to this day, the most thermally efficient : A sphere or sphere section has the lowest surface-to-volume ratio of any geometric shape. For a given cylinder volume, less combustion heat will be exposed to chamber surface area and absorbed by the engine's mass, so more energy is potentially be available to be turned into power.

2. Combustion efficiency: However, today we know that this thermal efficiency does not necessarily translate into combustion efficiency: that is, how much fuel is actually turned into power. The hemi's squish/quench qualities are relatively poor, so there is less turbulence in the chamber, a less homogeneous air/fuel charge, and less efficient combustion overall...despite the higher thermal efficiency.

3. Volumetric efficiency: The pentroof, four-valve combustion chamber is not particularly themally efficient, and its squish/quench properties aren't so great either. Essentially, there is no room for a squish zone. However: four valves per cylinder allow greater valve area per unit of bore area, for greater volumetric efficiency. Simply put, better breathing. Meanwhile, the manufacturers have learned how to use "tumble" and "swirl," rather than quench/squish, to generate the necessary turbulence for good combustion efficiency. (The narrow valve angles of today are all about tumble and swirl.)

It is clear that the real advantage of the classic two-valve hemi for much of its working life was not the greater thermal efficiency of the chamber shape. Rather, the valve locations imposed by the design virtually gauranteed a crossflow layout with adequate port volumes.

But not invariably. In 1903 Napier built an engine that was both a hemi and an F-head at the same time. The combustion chamber itself was about as close to an ideal hemispherical shape as possible. Meanwhile, the intake and exhaust valves, intake directly over exhaust, resided in a sort of antechamber stuck on the side of the cylinder. So theoretically at least, this engine's thermal efficiency would have been fine, but in practice its volumetric efficiency must have been horrible..and overall we would have to consider it primitive by modern standards.

[Ray Bell]

In reading some of this, one might conclude that narrow valve (included) angles are a goal pursued by modern engine designers, whereas they are in fact a product of modern design requirements, principally pursuit of compression ratios without the need for lumpy pistons.

[VAR1016]

Originally posted by Ray Bell
In reading some of this, one might conclude that narrow valve (included) angles are a goal pursued by modern engine designers, whereas they are in fact a product of modern design requirements, principally pursuit of compression ratios without the need for lumpy pistons.

First compliments to McGuire for a typically elegant and well-reasoned posting.

reading these postings reminds me of the story of he 2.5 litre BRM engine.

Stuart Tresillian originally conceived the engine as an ultra short-stroke and of course large-bore design. Anticipating (correctly in my view) the potential that the 102mm bore had for large valve area, a sine qua non in racing engine design, he drew a four-valve head. When he fell out with those in charge, Berthon took over the engine and converted the design to a more simple one with two enormous valves, a classic case of missed opportunity: four-valve designs had been proven in aero engine applications more than 15 years earlier, presumably the metallurgical problems having been solved. Berthon with much help from Tony Rudd eventually got the engine to be very powerful but really he was attacking the problem the wrong way. I claim no special knowledge, but by the mid 'fifties, I suspect that the science and measurement of the combustion process were much improved. Had the four-valve version been developed, then I am sure that its use would have been justified by the results.

Regarding the pistons being lumpy, well here of course we are getting involved in matters of burn time and flame front length. A flat-topped piston will inevitably present a shorter distance (and a smaller area for the thermal efficiency department).

Since compression ratio is so important for B.M.E.P. and we want large valve area (and large piston area of course), the four-valve pent roof or perhaps a variation of it, becomes the only viable option - that is as long as one insists on poppet valves.

I am really enjoying this thread

PdeRL

[rdrcr]

Originally posted by McGuire


...and of course, it has been suggested more than once that Duntov, in turn, "borrowed" the pushrod-hemi configuration from Talbot.

This is the first time I have seen it suggested that Ford Motor Co was connected or involved with Ardun in any way. Do you know of any primary sources which confirm this?

No, not directly and after a brief search was unable to come up with any. However, I have seen numerous secondary references to this detail. I wonder if Karl Ludvigsen would have a definitive word on this?

[Ray Bell]

I wonder if anyone has any detail on the Tornado heads?

[robert dick]

In 1900 the Buchet tricycle driven by Victor Rigal and the Buchet engined Perfecta tricycle driven by Paul Baras were quite successful in the Pau-Bayonne, Paris-Roubaix, Paris-Toulouse races.
Buchet engine : two-cylinder - hemispherical head : exhaust vertical in the head, mechanically operated via pushrods and rockers - intake inclined in the head, "automatic".
Such a Buchet engine was also used in Santos-Dumont's airship no. 4.
E. Buchet was born in Nantes/1860, died in Levallois/1902.
In 1899 the Buchet shop was located at no. 168, Avenue Daumesnil, Paris, in 1900 at no. 15, Rue Greffulhe, Levallois-Perret:
"Moteurs pour tricycles et motocyclettes - tricycles et quadricycles".

The Belgian Pipe appeared in the 1904 Bennett Cup. It was designed by ex-Daimler/Mercedes engineer Otto Pfänder : two low mounted camshafts, intake and exhaust inclined at 60 degrees to the cylinder axis, operation via pushrods and rockers - in principle the same system was used later in the Riley/ERA and the post-WWII Talbot-Lago (with higher mounted camshafts). In eight-litre form the Pipe finished second in the 1907 Kaiserpreis (driven by Hautvast).

The Fiat which won the 1907 GP (driven by Nazzaro) appeared in the 1905 Bennett Cup (of course the Fiat was improved in detail during 1906 and 1907). It was designed by Giovanni Enrico and Cesare Momo : one low mounted camshaft, intake and exhaust inclined at 30 degrees to the cylinder axis, operation via pushrods and rockers.

[dretceterini]

Thoughts please on what everyone would consider to be the ideal cylinder head design.

Has anyone ever tried something like what I would call a "reverse-hemi" or reverse-pent roof", where the top of the piston is actually "dish" shaped and the combusion chamber extends downward, ito the cylinder itself?

Would this help, as the piston, on it's upward compression stroke, would create a lot of "swirl"...


Thanks,
Stu

[McGuire]

Originally posted by VAR1016
It also has to do with valve angles; modern heads use valve included angles as low as 23 degrees - perhaps less. this would be impossible with a hemisphere unless of course one had very tiny valves.

PdeRL

The Peugeot 403 employed two laterally opposed valves at an included angle of 24 degrees. (The exhaust was nearly vertical.) It invariably has been regarded as a "hemi." Is it? I suppose that depends how far one wishes to stretch the rather elastic concept of "hemsipherical." (In strict dictionary terms, a perfect sphere bisected by exactly 50%...there may be no such engine in existence.) It did use a fully open chamber of roughly spherical configuration with no quench area, so...?

What is impossible in any sense is a hemi with four valves, unless they are disposed in more than two planes. With four valves in two planes we are essentially stuck with a pentroof configuration. So if we are talking about modern four-valve engines, we are not really talking about the classic hemi. We have changed the subject a bit, despite the similarities in cross-sectional view.

[VAR1016]

Originally posted by McGuire


The Peugeot 403 employed two laterally opposed valves at an included angle of 24 degrees. (The exhaust was nearly vertical.) It invariably has been regarded as a "hemi." Is it? I suppose that depends how far one wishes to stretch the rather elastic concept of "hemsipherical." (In strict dictionary terms, a perfect sphere bisected by exactly 50%...there may be no such engine in existence.) It did use a fully open chamber of roughly spherical configuration with no quench area, so...?

What is impossible in any sense is a hemi with four valves, unless they are disposed in more than two planes. With four valves in two planes we are essentially stuck with a pentroof configuration. So if we are talking about modern four-valve engines, we are not really talking about the classic hemi. We have changed the subject a bit, despite the similarities in cross-sectional view.

Last night I had a look at some head section drawings and really, one could describe some of them as being more conical than hemispherical!

Certainly the 1950s and 1960s Alfa-Romeo engines and the Aston Martin DB4 (a sort of "tribute" to the Alfa!) had combustion chambers that resembled hemispheres.

With regard to four valves in a "hemisphere" this could perhaps be achieved by disposing the valves radially as in that fascinating BMW F2 engine that was made about 1968.

PdeRL

[dretceterini]

I'm not trying to change the direction of the thread, but what about the location of the sparkplugs and the intake? The early Matras (for example) had the injectors at the top and the plug on the side, and the later versions were pretty much vice-versa. Does it really matter? Does anyone think the two injectors and two exhausts per cylinder, as on the BMW F2 car really help?

Thoughts please..

Stu

[McGuire]

Originally posted by robert dick
The Belgian Pipe appeared in the 1904 Bennett Cup. It was designed by ex-Daimler/Mercedes engineer Otto Pfänder : two low mounted camshafts, intake and exhaust inclined at 60 degrees to the cylinder axis, operation via pushrods and rockers - in principle the same system was used later in the Riley/ERA and the post-WWII Talbot-Lago (with higher mounted camshafts). In eight-litre form the Pipe finished second in the 1907 Kaiserpreis (driven by Hautvast).

If one is ever in Indianapolis, there is a remarkable machine on display at the Speedway Museum worth careful study: the 1903 Premier designed by George A. Weidley for Carl Fisher.

Built in 1903 (at least that is the claim) for the 1904 Vanderbilt Cup, it did not compete as at over 2500 lbs it was too heavy to meet the 2200 lb maximum weight rule. But relevant here is its engine: a 7"x 6" air-cooled inline four, it used a single overhead camshaft deployed over the centerline of the cylinders, pivoting lever followers, and two opposed valves per cylinder at an included angle of approximately 90 degrees, with hemispherical combustion chambers.

I don't make any claims for historical firsts for this vehicle, if for no other reason than those contests are not really my thing. But the Premier certainly merits a careful look: For one thing, this incredible piece of blacksmithing exists in pristine original condition. Whatever it is, it is what it is, and it is still here for us to examine today.

[robert dick]

Originally posted by McGuire


What is impossible in any sense is a hemi with four valves, unless they are disposed in more than two planes...

Hemi-four-valve head of the F2 BMW in the original Apfelbeck configuration - rather tricky :
http://www.02-club.d...ik/viervent.htm

[McGuire]

Originally posted by dretceterini
Based on what I have found, I would tend to agree.

It seems many of the early dohc motors, no matter if they were pushrod or actual dohcs had a pent roof combustion chamber, which would be more effective....so I don't really understand the development of the round "hemi" combustion chamber design after circa 1915...

Something interesting: the original 4-valve configuration as advanced by Peugeot and les Charlatans before WWI has not proceeded unbroken unto today. So while the Peugeot layout was predictive, it was not truly trend-setting.

By the early 1920's, automotive and motor racing practice had mainly "regressed" from the four-valve pentroof to the two-valve, classic "hemi" layout...with a few exceptions, like Leo Goosen's Offenhauser. (Meanwhile, the Novi and Offy midget engine were two-valvers.) The two-valve was not really displaced by the four-valve until well into the 1960s. Porsche, Aston-Martin, Jaguar, Ferrari, Coventry-Climax, Alfa, etc...all stuck mainly to two-valve engines, producing a four-valve here and there. There is a table in the back of Borgeson's The Classic Twin Cam Engine whch underlines this interesting trend.

I think we can chalk it up to the (apparent) fact that in two-valve form these engines had all the breathing capability they could use. Four valves added unjustified weight, cost, and complexity, evidently. However, in aircraft practice...

[McGuire]

Originally posted by robert dick


Hemi-four-valve head of the F2 BMW in the original Apfelbeck configuration - rather tricky :
http://www.02-club.d...ik/viervent.htm

Sure. Note the valves are indeed disposed in more than two planes, as I indicated.

In less radical aspect, contemporary F1 engines have headed off slightly in this direction. The use of finger followers, introduced for better lift geometry over the traditional bucket follower, also allows each of the valves in the intake and exhaust valve pairs to be splayed in the longitudinal plane -- around five to seven degrees.

[VAR1016]

Originally posted by McGuire


... In less radical aspect, contemporary F1 engines have headed off slightly in this direction. The use of finger followers, introduced for better lift geometry over the traditional bucket follower, ...

What goes around comes around!

Consider the 1926 Straight-8 Delage.

PdeRL

[McGuire]

Originally posted by VAR1016


First compliments to McGuire for a typically elegant and well-reasoned posting.

You are far too kind. When reviewing my posts I am usually thinking Jeez, what a crank. "With four valves disposed in two planes..." All this stuff needs is a quote or two from Ecclesiastes and it would read like LJK Setright.

[McGuire]

Originally posted by VAR1016
I am really enjoying this thread

PdeRL

Me too. Isn't the Internet wonderful? There may be only a handful of people on the entire planet who give a rat's ass about these things, but thanks to the World Wide Web we have managed to find each other. Thus we can spend our time boring each other interminably over questions such as these, instead of our families and friends. A boon to mankind, if you ask me.

[McGuire]

Originally posted by McGuire


Meanwhile, the manufacturers have learned how to use "tumble" and "swirl," rather than quench/squish, to generate the necessary turbulence for good combustion efficiency.

Or as they are known in some quarters, stumble and twirl.

[VAR1016]

Originally posted by McGuire


Me too. Isn't the Internet wonderful? There may be only a handful of people on the entire planet who give a rat's ass about these things, but thanks to the World Wide Web we have managed to find each other. Thus we can spend our time boring each other interminably over questions such as these, instead of our families and friends. A boon to mankind, if you ask me.

Yes indeed - the Internet is wonderful.

Wife went years ago - no children - almost all my friends are Lancia cranks.

Thank god for the Internet!

PdeRL

[rdrcr]

"...Lo, this only have I found, that God hath made man upright; but they have sought out many inventions..."

"...There may be only a handful of people on the entire planet who give a rat's ass about these things, but thanks to the World Wide Web we have managed to find each other. Thus we can spend our time boring each other interminably over questions such as these..."

Ahh, but the reality is, that I now have a better understanding and appreciation of how and why my '67 Charger can boil the rear tires off in an afternoon.

Translation: (love this thread)

[dretceterini]

Originally posted by robert dick


Hemi-four-valve head of the F2 BMW in the original Apfelbeck configuration - rather tricky :
http://www.02-club.d...ik/viervent.htm

The BMW motor is EXTREMELY interesting to me. I wonder just how much good the second set of injectors and two sets of exhausts actually did....270 hp out of 1600cc in 1968 is pretty damn impressive....

Stu

[VAR1016]

Originally posted by dretceterini


The BMW motor is EXTREMELY interesting to me. I wonder just how much good the second set of injectors and two sets of exhausts actually did....270 hp out of 1600cc in 1968 is pretty damn impressive....

Stu

I think that it was 2-litres (i.e. I was wrong when I wrote F2) and intended for the 2002 racers as shown in the picture.

PdeRL

EDIT:

I see that the original article does mention F2: unfortunately my German is non-existant - Holger are you there?

I recall that Ferrari's V-6 1600 F2 engine of 1968 made about 230HP - 270 would be very impressive. I think that the 270 must be from the 2-litre version - by way of comparison consider the Lucas-injected and very successful Cosworth BD 2-litre which made about 285HP some years later.

[dretceterini]

According to this, it's a 1600 and not a 2 liter...

"When the new 1600cc F2 regulations arrived in 1967 BMW produced an engine with an unusual four-valve Apfelbeck head in a Lola 100 chassis for drivers Jo Siffert and Hubert Hahne. The latter finished fourth in the Eifelrennen that year but success was rather limited and most of 1968 was spent developing a new car in association with Lola."


Stu

[VAR1016]

Originally posted by dretceterini
According to this, it's a 1600 and not a 2 liter...

"When the new 1600cc F2 regulations arrived in 1967 BMW produced an engine with an unusual four-valve Apfelbeck head in a Lola 100 chassis for drivers Jo Siffert and Hubert Hahne. The latter finished fourth in the Eifelrennen that year but success was rather limited and most of 1968 was spent developing a new car in association with Lola."


Stu

Fair enough; but did this engine produce 270HP? I ask because on that site there are references to the touring cars.

PdeRL

[Roger Clark]

Originally posted by VAR1016


First compliments to McGuire for a typically elegant and well-reasoned posting.

reading these postings reminds me of the story of he 2.5 litre BRM engine.

Stuart Tresillian originally conceived the engine as an ultra short-stroke and of course large-bore design. Anticipating (correctly in my view) the potential that the 102mm bore had for large valve area, a sine qua non in racing engine design, he drew a four-valve head. When he fell out with those in charge, Berthon took over the engine and converted the design to a more simple one with two enormous valves, a classic case of missed opportunity: four-valve designs had been proven in aero engine applications more than 15 years earlier, presumably the metallurgical problems having been solved. Berthon with much help from Tony Rudd eventually got the engine to be very powerful but really he was attacking the problem the wrong way. I claim no special knowledge, but by the mid 'fifties, I suspect that the science and measurement of the combustion process were much improved. Had the four-valve version been developed, then I am sure that its use would have been justified by the results.

Regarding the pistons being lumpy, well here of course we are getting involved in matters of burn time and flame front length. A flat-topped piston will inevitably present a shorter distance (and a smaller area for the thermal efficiency department).

Since compression ratio is so important for B.M.E.P. and we want large valve area (and large piston area of course), the four-valve pent roof or perhaps a variation of it, becomes the only viable option - that is as long as one insists on poppet valves.

I am really enjoying this thread

PdeRL

Of course, at around the same time as BRM were developing the 2.5 litre engine, Daimler-Benz were producing the M196. DB had used 4-valves per cylinder for their pre-war racing engines, but now switched to 2-valves, very large ones like the BRM, but desmodromically operated. It is possible that a 4-valve BRM engine would have been more successful, but most of Berthon's contempories preferred the simpler option. Given the problems that many of them, including BRM themselves, had with 4-vlalve engines in the years 61-65, they may have been right.

[VAR1016]

Originally posted by Roger Clark

Of course, at around the same time as BRM were developing the 2.5 litre engine, Daimler-Benz were producing the M196. DB had used 4-valves per cylinder for their pre-war racing engines, but now switched to 2-valves, very large ones like the BRM, but desmodromically operated. It is possible that a 4-valve BRM engine would have been more successful, but most of Berthon's contempories preferred the simpler option. Given the problems that many of them, including BRM themselves, had with 4-vlalve engines in the years 61-65, they may have been right.

Yes that's true of course.

However, the Mercedes-Benz was a straight-eight and at the time it may have been thought that given the valve area perceived to be necessary for a 312c.c. cylinder plus the complexities of desmodromic operation, that two valves would suffice.

BRM's engine had a bore of 102mm; this really needed four valves. Once BRM found the heads falling off the huge built-up valves that were being used, solid valves were used to replace them; the weight meant a reduction of abut 1000rpm; four valves could have solved this and with the nitro used to replace the lost power, more could have been obtained.

PdeRL

[McGuire]

Originally posted by dretceterini


The BMW motor is EXTREMELY interesting to me. I wonder just how much good the second set of injectors and two sets of exhausts actually did....270 hp out of 1600cc in 1968 is pretty damn impressive....

Stu

I could easily be wrong, but I believe this engine made the quoted 270 hp in two-liter form, but was not successful when the formula was reduced to 1.6 liters...leading to a falling-out between Roche and what's-his-name...Apfelbeck.

This engine was very tall, due to the vertical intake-port scheme, and heavy due to requiring double everything (throttle housings, exhaust headers etc). I remember something like 325-350 lbs. That's probably that's one of the reasons the idea was never pursued...that, and a great many technical difficulties generated for a potentially small gain. I wouldn't want to be the mechanic responsible for adjusting the valve lash on the thing. Still, it is an extremely interesting engine, as you say.

[McGuire]

Originally posted by VAR1016
BRM's engine had a bore of 102mm; this really needed four valves. Once BRM found the heads falling off the huge built-up valves that were being used, solid valves were used to replace them; the weight meant a reduction of abut 1000rpm; four valves could have solved this and with the nitro used to replace the lost power, more could have been obtained.

PdeRL

Yes, four more valves, but why stop there? Put four more cylinders under them and then you've got something. Still, I'm not sure the engine was the P25's chief problem.