Talk:Flathead engine

Has it got a hemi?
I added:
 * "though they were the basis of many early racing engines, including famous names such as Ardun (Zora Duntov) and Frontenac (Louis Chevrolet)."

I can't cite a source offhand, but it's well known. Google "Ardun" & "hemi" & you'll get several websites with details that agree with what I've read. Or goto the Hot Rod, Street Rodder, or like sites... Trekphiler 13:47, 4 January 2007 (UTC)

Howzabout a diagram?
Picture worth a Kiloword... —Preceding unsigned comment added by 199.175.128.1 (talk) 20:23, 3 April 2008 (UTC)

Cold starting
Starting side valve engines in cold weather was always a problem - I've pushed one or two! This could be listed as a disadvantage of them. Soarhead77 (talk) 18:41, 16 June 2008 (UTC)

my changes
Sorry I can't cite more references (unless you count Hot Rod Lincoln) but I don't think I have said anything that is not common knowledge or easily verifiable by looking at engines or drawings. I have a brother who is a racing mechanic specializing in old engines, so I have some contact with anecdotal knowledge as well as with the theoretical. In agreement with a post above, I think it would impair this article to require everything to have a standard published source. The subject is empirical engineering.

Flat head is still a four-stroke
In the 'Popular Culture' section I removed the statement that indicates a flathead has more power strokes per revolution. Whoever said that was confusing the L head engine with a two stroke engine, which does have a power stroke every revolution, whereas four-stroke engines (OHV, L-head, or any other configuration) have a power stroke every two revolutions (per cylinder). —Preceding unsigned comment added by 67.250.57.16 (talk) 20:46, 27 February 2011 (UTC)

Cam-in-block at AfD
See Articles for deletion/Cam-in-block Andy Dingley (talk) 10:18, 14 April 2012 (UTC)

No Pushrods?
In the photograph, Im not understanding what Im seeing. It looks like each cylinder block has two pushrod tubes, but if its a flathead, then they're not pushrod tubes. So what am I seeing? Marc S. Dania fl. 206.192.35.125 (talk) 13:22, 22 April 2013 (UTC)


 * They're pushrod tubes. Sidevalves can have pushrods (or simply very long valve stems), they just don't have rockers. This is most noticeable where the camshaft is mounted low down and the stroke or cylinders are long. Andy Dingley (talk) 14:14, 22 April 2013 (UTC)

Not true: Indian V-twin motorcycle engines all have rocker arms. The essential feature of the flathead engine is that the valves reside in the block (not the head), and open upward into the combustion chamber. The wide variety of valve gear is not definitive.


 * In a schematic diagram, I saw one valve.  Is it correct to assume some flatheads have one valve per cylinder, and some have two per cylinder?   Marc S.  Dania Fl  206.192.35.125 (talk) 19:01, 22 April 2013 (UTC)
 * They have two valves per cylinder - inlet and exhaust.
 * There are some rare engines that don't have two. One arrangement is the IOE engine (one sidevalve, one overhead). An early form of this had an exhaust valve and the inlet valve was an automatic spring-loaded valve. Another is the monosoupape (French: single valve), where there's an exhaust valve, which also acts as an inlet valve for air and fuel and other air comes in via the crankcase. A further design is the two-stroke single-valve uniflow diesel engine, where the inlet is piston-ported through the cylinder wall and there's a single exhaust valve. Andy Dingley (talk) 21:32, 22 April 2013 (UTC)
 * Not knowing which schematic diagram you refer to, but it is quite usual to illustrate the L-head such way that the other valve hides behind the one that is visible. The same thing with 4-valve DOHC – you see two valves in the illustration while there should be four. –Nikolas Ojala (talk) 11:45, 22 April 2014 (UTC)

Article partion 3. Potentials Should be removed.
As headline says, potentials part of the article should be removed, as it is based solely on oppinion that is not neutral nor does it have plausible citations. And to make things clear, i will explain it further. Pop-up pistons are piston type. It should be adressed in it`s own article, piston. Pop-up piston is type of the piston crown. It is regularly used in all kind of piston engines among other dome shapes and sizes. "Turbulence grooves", also known as Somender Singh grooves are not proven anywhere to be working concept. citing patent, youtube or even available vague articles or mr. singhs own web page should not be considered credible citations. Turbulence grooves are purely speculative. Cup valves has not been in use in any application. Test results are not available. Patents are not credible citations. workings of cup valve is purely speculative. Laser ignition is in develobment stage, and there is no test data available. Workings of laser ignition is purely speculative, at this point. And on top of things, sentence "Although OHV and OHC engines have beaten flatheads in power and fuel efficiency contest, flatheads still have unused potentials for better performance." is misleading. It implies that fundamental flaws of old engine desingn could be overcomed. It is just not true. Flathead is cool engine and important piece of automotive history. But nevertheless, it is obsolete desing, not unused "potential". Heikki Vainionpää (talk) 14:06, 18 June 2014 (UTC)
 * To see why sidevalve engines (at least, the IOE layout) aren't obsolete, look at the best of their engine designs from the 1950s, like the Rover and the Rolls-Royce B series. After Ricardo's work in the 1920s, the sidevalve engine became as efficient as any other layout for the same cost. To make a low-cost Otto cycle engine burning low-quality fuels, IOE still has advantages, even today. Andy Dingley (talk) 14:35, 18 June 2014 (UTC)
 * That is just not true. Sidevalve engines are not in anywhere near as efficient as valve-in-head arrangement. Even most lawnmover motors today is valve-in-head design. I`m not arquing about advantages of flathead engine, but the fact is sidevalve engines is not efficient design. It has poor combustion chamber, that comes by design. Crossflow design included. Don`t get me wrong, i like flathead engines and think they are cool, but it just does not make it efficient design.

Heikki Vainionpää (talk) 21:23, 18 June 2014 (UTC)


 * The first section on using popups is well cited. Hot Rod is by all measures a reliable source, so I'm inclined to leave that in.  They didn't just mention it, they have an entire article on it and a demonstrator engine show in the images, and they are saying it is a currently used technology.  Even if it was moved, I think this is clearly worth keeping


 * The second section is support by a patent and weak youtube video, but it is showing actual applications and methods, so I'm not as fixed here, but inclined to keep.


 * Next we see a claim to use cupped valves instead of poppet valves. Again we have a patents, so I'm not fixed, but I lean towards keeping because it add information about the fact that people have at least studied it, enough to invent methods worthy of getting a patent.


 * The forth section is purely speculative, and at 10k for a laser array, never likely to see real applications. Original research worth deleting.


 * If you think these are invalid methods, then by all means add a criticism section under this and provide sources disputing these claims. (Note that the popup is pretty much proven and being done, but if you had sources specific to it, then include them) Or make a sourced header to this section saying that much of these are hypothetical and not everyone agrees with their ability to have practical application. I'm just not confident that removing all of this is improving the encyclopedia. Some of it can go, rewrite some, provide contradictory sources if they exist, but not wholesale deletion. I would prefer to leave this open a while and get input from a number of people, if you don't mind. Dennis Brown &#124; 2¢ &#124;  WER  14:37, 18 June 2014 (UTC)
 * Leave it in. As a general encyclopedia, even hot rodders' work deserves a mention (if every Pokémon character does...) And it's not like nobody uses flatheads, either. If there's info on improved steam engines...  TREKphiler   any time you're ready, Uhura  19:13, 18 June 2014 (UTC)
 * Pop-up pistons is cited as it should. And i think it does not even need citing, as it is piston design that is used commonly. But as different dome shapes are used to raise or lover compression ratio in all piston engines. It does not make specifically flathead engine any more potential. Proper place for talking about pop-up piston, would be Piston article.

Citing patents are not plausible facts. Patent is not proof of concept. You could patent ideas. Cup valve for example, is not used anywhere. It is just a concept, and not very good of that. Turbulence grooves are patented over 13 years ago, and there is not single proof that they work. Only Briggs and Stratton has been agreed to test them, and even they are not interested in them. Claiming that they could be used to overcome inherently poor combustion chamber, is just not true.

I am not going to make section that disaproves what is claimed. It would make the article incoherent and ambiquous. How would that be improvement of encyclopedia? The main reason why i think that Potentials part of the article should be removed, is just the fact that it is only oppinion without any concrete evidence. Heikki Vainionpää (talk) 21:23, 18 June 2014 (UTC)
 * The first section is absolutely proven, and was done so by Hot Rod. Also, basic engine theory alone would demonstrate that popups increase compression ratio, and the average flathead is a low compression engine, thus it would improve performance.  The others are talking about patents without direct proof, granted.  The problem is that you are saying "they are not plausible" but you aren't providing an basis for that belief, and again, in at least one example, I'm very confident you are mistaken.   Dennis Brown &#124; 2¢ &#124;  WER  21:29, 18 June 2014 (UTC)
 * Could you please state, in which example i am or you think i am incorrect? Patent is a poor citation, because it does not prove anything. It does not have to. Patents is used to kind of copywrighting certain kind of structures. If we take Somender grooves for example, patents descripes the crooves visually and verbally. Of course their function is descriped too, but there is no factual data about their workings. Concerning pop-up piston, as i sayed, i don`t arque about its benefits. And it has been proven with far more credible sources than hot rod magazine. Put place for pop-up piston is in article piston, not flathead. Specifically stating about pop-up pistons in this flathead article, is like saying "it hurts when i hit my head with a hammer." Sure, it enhances flatheads performance, as compression ratio is raised. But when you increase the compression ratio, you take off the flatheads advantage which comes from low compression ratio, like fuel insensitivity. If you increase engines compression, it can not use low octane fuel. There`s basic engine theory for you.Heikki Vainionpää (talk) 08:52, 19 June 2014 (UTC)
 * I'm finding it (as usual) hard to address your points when there are so many of them in one large edit.
 * "Pop up pistons" aren't a specific type of piston, they're a particular installation of a relatively standard flat-topped piston, so that the piston crown rises above the deck height. Now obviously this needs a top ring that's not too high up the piston, but that's not unusual for older piston designs. Discussion of pop-up pistons shouldn't be WP:UNDUE, but it belongs here in the sidevalve article, not at piston.
 * The purpose of a pop up piston isn't to increase CR either. It's easier to increase CR by simply reducing the combustion chamber volume, as usual. Pop up does increase CR, but as a secondary side effect and not by much. The real purpose of pop up is to increase squish, by reducing the dead volume above the piston in favour of volume over to the side, near the spark plug and the more active area of the combustion chamber. The big risk of an inefficient sidevalve design is a long flat combustion chamber with poor combustion performance. Increasing the squish (more importantly than the CR) improves this.
 * As a kid in the '60s & '70s, I was taught that sidevalves were obsolete, OHV was a cheap compromise and OHC or DOHC was the only interesting direction for the future. When I actually learned something about engine design though (and there's still no substitute for reading all the Ricardos, cover to cover) I learned that the sidevalve was improved so much in the 1920s that many of its previous disadvantages were removed then. As a means of designing low-cost low-speed engines for efficient spark ignition, Otto cycle combustion (fuel specific, not capacity or engine weight specific) with low octane fuels though (i.e. paraffin / kerosene), the well-designed IOE is still not obsolete to a degree that should be abandoned. This is something of an irrelevance these days, as biofuels are offering more fuels suitable for compression ignition engines than spark ignition, and extra-high efficiency is returning to the original Diesel cycle rather than Otto. However this doesn't invalidate the niche demonstrated by the sidevalve. Andy Dingley (talk) 09:27, 19 June 2014 (UTC)


 * Im sorry i could not met your standards when replying.


 * Pop-up piston is one design of the piston, that is used regularly in many types of piston engines. Like open chambered big block mopar or 318 poly engine. They can also benefit, when used piston that goes higher than deck level. And effective quench can be archieved, but it comes from different fact than just using pop-up type piston desing. It comes from tight quench area, that may or may not be archieved using pop-up piston. It is matter of piston to head(on the quench area) clearance.


 * Pop-up piston raises compression ratio, no matter how you use it. It does not necessarily mean that there would be effective quench. You could archieve effective quench by other means too.


 * I agree, that there are still uses for sidevalve design. Like the Belgian D-motor. But that does not make up the fact that almost every aspect of sidevalve engines could be done better and more efficiently with valve-in-head design. There are only minor advantages in reliability or packaging that could make sidevalve viable option. When it comes in biofuels and alternative fuels, same benefits can be archieved in valve-in-head design. biggest problem with sidevalves are actually the sidevalves. That makes the compression chamber poor and makes poor valveflow.

¨¨¨¨ — Preceding unsigned comment added by Heikki Vainionpää (talk • contribs) 11:57, 19 June 2014 (UTC)
 * So what's your point here? That sidevalves shouldn't be discussed? That later innovations in sidevalves shouldn't be discussed? That current innovations shouldn't be discussed? You mention the D-motor, now there's an example where some very narrow advantages (reliability for aircraft use) justify sidevalves for what would otherwise be a very strange engine indeed. Yet this is a citable and notable example where neither of us are claiming the sidevalve still has a future, but an independent developer is.
 * Just what are you trying to remove here, and on what basis? Andy Dingley (talk) 13:04, 19 June 2014 (UTC)


 * I have sayed it many times. Even the headline of this talk says what i am suggesting. Removing part that claims something, what can only be descriped as oppinion. I think that using patent as a proof of concept, is vague at best. Patents does not prove anything, and that is a fact. You can patent anything you want, if it just meets requirements. It does not actually mean that it will work or it does not mean that it would be in anyway potential option. Thats it. Concerning about pop-up piston, i just think it is in wrong place. If you want, you could mention it in the article. But as i sayed, i don`t think it is necessary, as it is not flathead specific item.


 * Sidevalves are discussed, and should be discussed. I never claimed that it should not be discussed. You just wanted to read that. But that is not true, as it is a interesting engine. And i am discussing about flatheads at the moment, on the other forum. This is not, in my oppinion, place to discuss it. Wikipedia should give neutral description about the subject. There is many uses for flathead. You can still use one on your car, and that is fine. I even want one in my project. But in reality, it has very little real world advantages when compared to modern valve-in-head engines. Only real advantages that i can see, compared to modern engines is that you can`t drop valve on top of piston, and it can be made more compact on height. It would be still wider than valve-in-head. Nissan Has good example about compactness of OHC design. Every other advantage has been or could be overcomed in valve-in-head desing.

You can see Nissan engine here http://www.gizmag.com/nissan-zeod-rc-engine/30611/


 * D-motor is a good example of the application, where using sidevalve is justified. I would love to have that little extra security that valve arrangement allows, when flying. And it is light and compact engine. And as there is no need for huge power and there is no tight emission requirements to be fulfilled. It is just good choise in that application.

Heikki Vainionpää (talk) 21:07, 19 June 2014 (UTC)


 * The Hot Rod article is one that discusses popups and improvements, how is it "disproven"? And even if something was commonly believed but disproven we would have a section on if there was good sources, as a common misconception.  We aren't here to provide the least amount of information, we are here to summarize what is known about them, and "potentials" is one thing that is known and sourced.  As for patents, they don't need to prove anything, we are just proving that someone bothered to patent something regarding those technologies.  Those are weaker keeps in my eyes, but I haven't seen a good argument to delete them. If anything, they might need to be expanded a bit.  It is pretty hard to find good encyclopedia grade information on flatheads, so if it is relevant to the topic, we kind of owe it to ourselves to properly expand, not delete. Dennis Brown &#124; 2¢ &#124;  WER  22:05, 19 June 2014 (UTC)


 * I begin to wonder if you read at all, what i have writed,. Or just purposely misunderstand. Or maybe you could point out the part where i tryed to "disprove" pop-up pistons?

And using patents as a reliable reference, Just google weird patents or strangest patents. Or read about patents technology companies patent, like google for example, who patented "Hand Gestures to Signify What is Important." It includes making heart shape by hand what teenagers are using, for example. Then tell me again how good references patents are? And how does unproven claims make better article? Finding reliable information about flatheads, or sidevalve arrangment to be more precise, is not hard. But finding something that actually proves or even supports the claims that are presented here, are really hard to find. And that is because they have no basis on real world. Heikki Vainionpää (talk) 12:09, 23 June 2014 (UTC)
 * I don't think we need to necessarily rely on the patent as a source, per se, and my opinion on those sections is weaker. I do think that a single paragraph mentioning the fact that two people have patented devices is worth noting.  Not to show the devices work, or have even been put into production, but to show there is enduring interest in the flathead design.  I could see rewording most of that entire section, but that isn't the same as deleting it.  There is some value in there, if modified. I think your insistence that they have "no basis in the real world" is hyperbole at best, and inaccurate.  For starters, a lack of sources doesn't disprove a fact.  And I don't recall stating we have to prove any of these patents do what they say, they can be used for other purposes, as I've pointed out.  So yes, I read what you are saying, but that doesn't mean I agree with your conclusions. Dennis Brown &#124; 2¢ &#124;  WER  18:37, 23 June 2014 (UTC)
 * So let me see if i get this correct. Even with lack of any kind of evidence that patent or even the idea works, is enough to claim their workings in sidevalve arrangement? Do we have consencus in that we can accept wild claims that patents make, as a reliable source?


 * Firs of all, cup valves have not been used in any application. Thats because it has inherent design flaws. It is far more complicated design compared to traditional valve. In flathead, that would not be beneficial, as simplicity is it`s advantage. Not to mention about cooling problems of cup valve, sealing problems and adverse effect to shape of the combustion chamber. Those would have adverse effect for emissions and efficiency. It has absolutely no advantages to be gained in real world. Cup valve, sleeve valve, rotary valve, swinging poppet valve, reed valve, you name it, are not used in automotive world, just because poppet valve is extremely efficient and simple design. Outside automotives, it might have some oddball advantage, that has not been invented yet.


 * Turbulence grooves has been tested only once. I mean really tested. In that application, Briggs and stratton sidevalve, it did use less fuel on very narrow range of rpm. That could come from many factors. But Emissions was increased, that tells us it really did not have better mixture of fuel charge. And it did not make more efficient combustion. Emissions tells us how efficient and good the combustion process was. So from the only actual test that has been done, proves the grooves do not make more efficien combustion. So I think it is justified to say, at this moment, that Somender singh grooves does not work.


 * Now, if we talk about laser ignition. This is no Star wars. It might be working concept. But no testing is done to that. Cost, complex design and marginal advantages would not make it potential choise to the engine, thats only advantages are simplicity and compactness.


 * And, now when we are at it, Pop-up pistons does not make combustion chamber any better. It does increase compression ratio. Making narrow squish band is what creates turbulence and removes mixture from the detonation prone area. That is something you can archieve with or without pop-up pistons.


 * But as this is not getting us nowhere, i would like to have oppinion of other administrators on the subject.Heikki Vainionpää (talk) 20:12, 30 June 2014 (UTC)

Its certainly a very peculiar section. Large parts of the article, especially this potential section, but also parts of the history and application section read as if they are written by a rabid side valve engine enthusiast. There's not much NPOV in sight. Citing the manufacturers web site as a reference for advantages of that side valve aero engine for example. A more neutral reference might be better. 212.159.44.170 (talk) 15:06, 20 October 2016 (UTC)

Propose change of name of article from "Flathead engine" to "Sidevalve engine"
I propose a change of name of this article from "Flathead engine" to "Sidevalve engine". "Flathead" is an American slang term that is neither used nor recognised in the remaining English-speaking world. Also, "sidevalve" more accurately and clearly describes the engine than does "flathead; after all, sidevalve heads are not flat! Arrivisto (talk) 11:44, 14 December 2014 (UTC)


 * Comment. I don't object to the page name change. But I must correct the notion that "flathead" is [solely] an American slang term. In the U.S. it is simply the normal term, period, to refer to sidevalve engines. It belongs to any register in which engine type may be discussed. For example, I grew up hearing mentions of the flathead engines that had formerly been common in cars, trucks, and tractors when the speakers were younger (1920s-1950s), and I never even heard "sidevalve" until I was an adult, when I found out that oh, OK, it's just a synonym of flathead. However, Americans today (in the Web era) need to know that "sidevalve" is a synonym and that much of the world uses it, just as they need to know that "petrol" is a synonym for gasoline and that much of the world uses it. In cases where "most people around the world know the American synonym" (which I believe is true of "gasoline"), it may be an academic point which one is heard or read. In cases where the American English norm is noticeably uncommon nearly everywhere else (which may be true of "flathead", I don't know), I feel that Wikipedia best serves readers by using the majority-prevalence term. — ¾-10 18:01, 14 December 2014 (UTC)


 * I've never called any engine a "flathead" in my life, except one quite specific series of Ford V8s. I've always known them as sidevalves.
 * However WP:ENGVAR is quite clear: whoever gets there first gets to choose. It is hard to rename articles away from that: either because there is a very clear local relation to the subject (not here) or because there are more US editors on WP than English-speaking Europeans, so the vote-counting approach will always move towards the US position.
 * Personally I would prefer sidevalve here, but recognise that I'd be ignored in that. Unlike the downright misleading cam-in-block article, at least here they are credibly close synonyms and so there's no major disadvantage. Andy Dingley (talk) 18:36, 14 December 2014 (UTC)


 * I agree that Sidevalve engine would be a better name, but as long as Sidevalve engine redirects to this article and the opening paragraph mentions both terms, I don't see a problem. ——Nikolas Ojala (talk) 04:17, 15 December 2014 (UTC)
 * I've always used flathead (& heard flathead much more commonly), but that may be a local (NAm) Engvar matter. I agree, so long as sidevalve is mentioned, it's not a big deal.  TREKphiler   any time you're ready, Uhura  16:52, 20 December 2014 (UTC)

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Original research
This sentence is original research: ″''These advantages may explain why overhead valve designs were first adopted only in high-performance applications (...), while economy cars, trucks, and agricultural engines continued to use flathead engines for some time. Even today, flatheads are common in lawnmowers, and basic farm machinery.''″

I decided to remove it from the article, and here is why:

First, there is no source for this sentence. Most importantly though, there is no time period given. And the rest appears unlikely. I tried looking up some engine examples in Hans List (Hrsg): Die Verbrennungskraftmaschine, Heft 11: H. Kremser: Der Aufbau schnellaufender Verbrennungskraftmaschinen für Kraftfahrzeuge und Triebwagen, Springer-Verlag, Wien 1942, ISBN 978-3-7091-5016-0 pp. 199 (released in 1942) and I found several good ones:


 * Engines for small passenger cars:


 * Fiat 500: Straight-4, 570 cm³, 13 PS, Flathead
 * Steyr 55: Flat-4, 1158 cm³, 25 PS, Flathead


 * Engines for passenger cars with medium power:


 * Adler Trumpf 1,7 l: Straight-4, 1645 cm³, 36 PS, Flathead
 * Ringhoffer Tatrawerke 97: Flat-4, 1749 cm³, 45, SOHC
 * Bayerische Motorenwerke 2 l: Straight-6, 1971 cm³, 55 PS, OHV
 * Steyr 630: Straight-6, 2260 cm³, 55 PS, OHV

The same book lists several truck engines:


 * Ford V 8-60 and V 8-85: Both Flathead
 * Mercedes-Benz M 159: OHV
 * Maybach DSO 8: OHV
 * Mercedes-Benz OM 138: OHV
 * Hercules engine: OHV
 * KHD S88D: OHV
 * MAN D0534 G: OHV
 * KHD F 4 M 513: OHV
 * Borgward D6M5: OHV

This makes it plausible that economy cars continued to use Flathead engines, but it is not evidence; also, some 1940's economy cars engines already had overhead valves. The first truck engine made by Benz & Cie. in 1924 named Benz OB 2 was an OHV engine. (Olaf von Fersen: Ein Jahrhundert Automobiltechnik. Nutzfahrzeuge. VDI-Verlag, Düsseldorf 1987, ISBN 3-18-400656-6, p. 126 and 127.) Only one of the truck engines listed by Kremser is not an OHV engine. Therefore, I think it's safe to say that the flathead design was never widely used for truck engines. Also, I have never seen agricultural vehicles with flathead engines. Usually, every agricultural tractor has an OHV engine (except for the Lanz Bulldog which has a hot bulb engine that doesn't need valves); historical Claas Combine harvesters usually have Claas, Perkins, Deutz, Mercedes-Benz, Ford or Volkswagen engines, I have never seen any of these without OHV valvetrain. I don't own a book I could cite at this point that lists common agricultural engines, however, I know some engines used in agricultural vehicles (most of them are standard industrial engines); all of them are OHV: Mercedes-Benz OM 636, Porsche F218, MWM AKD 112 Z, Steyr WD 113, KHD F3L 712, VW Typ 122, Perkins 6.354, Mercedes-Benz OM 352, etc. If required, I will cite sources that prove that these are all OHV engines. My personal experience: Flathead agricultural engines don't exist. Also, I have never seen lawnmower Flathead engines, lawnmower engines usually have OHV or OHC design. The only lawnmower flathead engine I know is the Briggs engine. Even other smaller engines usually aren't SV engines. Even 19th Century industrial Diesel engines aren't flathead engines; at least, I have never seen any. --Jojhnjoy (talk) 17:51, 4 October 2017 (UTC)
 * I've restored it. Past experience indicates that any attempt to discuss a topic with you will be fruitless. Should you really wish to understand this, then there is still no better source to read that Ricardo's standard textbooks on it (I would suggest the Ricardo & Clyde edition). Andy Dingley (talk) 22:34, 4 October 2017 (UTC)


 * As I explained, I seriously doubt that the content is not original research. There is no source for it (which means that this text must not be in the article). Deleting the text is the second best option to go with. The best option is finding sources and trying to figure out if the sentence is original research or not: So, what does the sentence express? It says: economy cars, trucks, and agricultural engines continued to use flathead engines for some time. Remember, there is no evidence for that. No source cited. I wondered about that sentence; the term "economy car" is not really defined and it could be true that SV engines were used for such vehicles in the 1940's; but I can say for sure that truck engines and agricultural engines arent's SV engines. And they have never been. The book by Hans List (!) from 1942 (!) lists only one industrial SV engine for trucks and agricultural vehicles. Rudolf Diesel never designed an SV engine. And there is evidence that compies such as Daimler-Benz, Claas, Deutz, MAN, Lanz, Fendt, Porsche, etc. never used SV engines for any of their agricultural vehicles. (I have to mention that the first four Unimog prototypes had SV engines; they were prototypes though and the engineers quickly decided to use an OHV engine instead. (Also, I could have missed some other prototypes.)) Even the first Benz truck engine was an OHV engine. I think this is sufficient to have serious doubt. If you have sources that prove that SV engines were used in agricultural vehicles and trucks for some time, cite them. But as long as there is no citation, the sentence has to be considered original research. Therefore, it must be removed. Past experience indicates that you would rather support public flogging than discussing with valid arguments (even though you appear like an engineer sometimes). But if you have a source for this sentence, then cite it. Otherwise it is just original research. Since you are obviously an experienced author, I assume that you know the core content policies of Wikipedia and where to find them: [Wikipedias] content is determined by previously published information rather than the beliefs or experiences of its editors. Even if you're sure something is true, it must be verifiable before you can add it. If you really want me to read the book, give me some more information. I recommend the following for you to read: H. Kremser: Der Aufbau schnellaufender Verbrennungskraftmaschinen für Kraftfahrzeuge und Triebwagen, Springer-Verlag, Wien 1942, ISBN 978-3-7091-5016-0. --Jojhnjoy (talk) 07:57, 6 October 2017 (UTC)
 * Shall we discuss your next topic ban here, or at ANI? Andy Dingley (talk) 09:06, 6 October 2017 (UTC)


 * Do you have anything useful to add here? --Jojhnjoy (talk) 09:24, 6 October 2017 (UTC)
 * Administrators'_noticeboard Andy Dingley (talk) 10:17, 6 October 2017 (UTC)
 * At a minimum, it deserves fact-tagging. (So does most of the page.) The named OHV engines above show a distinct European bias; in the U.S., the flatty's much more common, even in luxury marques.  TREKphiler  any time you're ready, Uhura  10:46, 6 October 2017 (UTC)


 * Okay then. Are there any books we could cite here? If so, I think the sentence could be changed to something like this: ″Despite the fact that overhead valves have advantages over side valves, some engine makers continued to use the flathead design until [TIME XYZ] because of [REASON XYZ]. While in [REGION XYZ] flathead engines where common for applications such as [APPLICATION XYZ] until [TIME XYZ], in Europe, SV engines were rather uncommon and by the early 1940's, they could be found in small passenger cars only. After WWII, even in small passenger cars the SV desgin was replaced by modern designs such as OHV and OHC.″ --Jojhnjoy (talk) 11:02, 6 October 2017 (UTC)


 * Yes, fact-tagging of the statement is warranted, and it could do with a wording tweak. But I do not believe it is Original Research (despite Jojhnjoy's accusation in his revenge-driven ANI), so the text should stay unless sources show it is incorrect.
 * By the way, Jojhnjoy is "indefinitely topic banned from any edits relating to automobile". At the bottom of this very page, it says this is an automobile article. 1292simon (talk) 11:54, 6 October 2017 (UTC)

Deletion.
I have deleted the "Potentials" paragraph. Of its three sections, I have edited, pruned and moved two and have deleted the third because (i) the citations are poor, and (ii) it applies to ohv engines, not flatheads. Arrivisto (talk) 12:54, 29 April 2018 (UTC)
 * Did you really check the references, all four of them? They were about flatheads. ——Nikolas Ojala (talk) 17:21, 29 April 2018 (UTC)
 * If you feel I have wrongly deleted the citations, please restore them; but I suggest don't reinstate the "Potentials" paragraph. Cheers! Arrivisto (talk) 18:43, 29 April 2018 (UTC)
 * "Turbulence grooves may increase swirl inside the combustion chamber, thus increasing torque, especially at low rpm." I can see how this might work on an ohv engine, but a flathead's combustion chamber is almost entirely above the valves. The flathead already has superb turbulence because of the massive squish and because of the circuitous gas flow. I cannot see how "turbulence grooves" would do anything but hinder effective cylinder filling. Arrivisto (talk) 08:10, 30 April 2018 (UTC)
 * "The flathead already has superb turbulence" Only if designed to have turbulence. There was little turbulence in them before Ricardo, and for the most common sidevalves today, the small engine 4-stroke lawnmowers et al., this lesson seems to have been lost. Effective turbulence is not caused by grooves within the chamber  (much the same myth as the deflector piston in early two strokes and the vain hope of horizontal axis loop scavenging, but rather (as Ricardo's turbulent head design first produced) an inlet charge which has an asymmetric flow, such that there's an overall curl to it (the longer path length and laminar flow in the float encourages a higher flow velocity in the upper, outer path, which then leads to the rolling motion within the cylinder, before the piston rises).  This used to be a much better article a few years ago, when it had some content, but it's back now to a US "my favourite motorbike" spotter's page. sic transit Wikipedia. Andy Dingley (talk) 08:49, 30 April 2018 (UTC)
 * I do not claim to be a expert on this content, but it appeared well sourced and supported. It was also clearly talking about the flathead attributes. -72bikers (talk) 14:00, 30 April 2018 (UTC)
 * "well sourced and supported" - not in any way that I can see!    There's a patent (WP hates patents as sources, as they're WP:PRIMARY sources and do not demonstrate that the invention works).  There' a Popular Science piece, which is more of the "plucky little inventor" human interest story and again, is not meeting WP:RS to show that it works. A dead web page and a YouTube video promising "Low Fule Consumption" [sic].
 * I'd love Mr Singh's invention to work. I can see much benefit to it in India, particularly as a sidevalve design does still have its place for low octane fuels. But optimism is not verification.
 * This is a dreadful article. It conveys almost nothing, it's bloated with car-spotting fandom and the claims that are here are both unbalanced as to which are important and which are not, and they're also pitifully sourced. Many strong claims here are just simply wrong (neither Rolls-Royce nor Rover were building F-head engines in the 1950s). Andy Dingley (talk) 14:10, 30 April 2018 (UTC)


 * Ouch did not mean to step on any toes. You say potato and I say potahto.72bikers (talk) 00:34, 1 May 2018 (UTC)


 * I recently discovered this page and I can't agree more with Andy Dingley. Initially, It was just this sentence that appeared suspicious: "Flathead designs have been used on a number of motorcycles, in particular (...) early BMW flat twins and Russian copies thereof" which I believe isn't true. There is actually no evidence for this and while some Russian vehicles were licensed/unlicensed copies of German vehicles, I have never heard of any BMW motorcycle copies. After taking a closer look it seems like some of the references are just comments, actually, this page represents what some authors believe, and there are no proper sources. It is really just a "my favourite motorbike" spotter's page consisting of original research. Richard Leemann (talk) 01:16, 1 May 2018 (UTC)
 * Dnepr and Ural both built copies of the BMW R71. These weren't "war booty" as often thought, but had been licensed officially by the Soviets, during the time of the Ribbentrop-Molotov pact. Andy Dingley (talk) 01:39, 1 May 2018 (UTC)
 * The sentence though made me believe that these copies were unlicensed copies. Do you have any evidence? I doubt that Germans would have given BMW-blueprints to the Soviets for free. Richard Leemann (talk) 13:43, 1 May 2018 (UTC)
 * They sold them (remember that Germany was skint until they could get some proper looting on). They were allies at the time. Rolls-Royce also developed the Merlin engine in a Heinkel He 70 they'd bought, as the fastest aircraft fuselage design then available. Andy Dingley (talk) 14:35, 1 May 2018 (UTC)

Declutter
In the light of recent comments, I propose to declutter the article and create a new page on "Flathead motorcycles" that will live or die on its own merits. On the Flathead page, it might be appropriate to have a paragraph on Ricardo and his work on squish & turbulence. There were other researchers too: see "Speed & how to obtain it" - once essential reading for racers riding matchless G50s, AJS 7Rs and Manx Nortons. Arrivisto (talk) 08:00, 1 May 2018 (UTC)
 * Given HD did use flatties for a substantial period, deleting the Harleys entire seems like a bad idea. Pruning the detail would have been better advised, wouldn't it? (FYI, not a HD fanboi.)  TREKphiler  any time you're ready, Uhura  08:36, 1 May 2018 (UTC)
 * I think when most people talk about flathead they would think Harley. 72bikers (talk) 13:41, 1 May 2018 (UTC)
 * No doubt the "Flathead motorcycles" page will disabuse them of such tunnel vision! Arrivisto (talk) 23:48, 2 May 2018 (UTC)

Advantages
This sentence makes no sense. "As these engines were designed to produce peak power at only 2800 rpm, their very low engine speed meant the designers could dispense with the complexity and weight of an OHV valvetrain." NO! This is backward. It is already dispensing with the complexity and weight of an OHV valvetrain. That's what makes it a flathead. That's the reason they can run at slow speed. The real advantage of running at slow speed it the absence of a gear reduction unit and its associated weight.Longinus876 (talk) 03:10, 5 August 2019 (UTC)


 * Fixed. Best regards, --Johannes (Talk) (Contribs) (Articles) 07:03, 6 August 2019 (UTC)

citation really needed?
Does a simply logical thing really need citation? A stuck valve can not collide with the piston because it is NOT in the piston path. This is obvious from the arrangement, no scientific evidence needed there. 81.200.57.130 (talk) 07:28, 29 August 2023 (UTC)