Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead | Pros and Cons
Valvetrain: OHV, SOHC, DOHC & Flathead | Explained
Valvetrain:
The valvetrain is a mechanical system in an internal combustion engine that manages the opening and closing of the intake and exhaust valves. Its purpose is to regulate the timing of these valve operations to allow the intake of air/fuel mixture into the combustion chamber and the expulsion of exhaust gases.
The intake valves are responsible for controlling the flow of the air/fuel mixture into the combustion chamber during the intake stroke. On the other hand, the exhaust valves regulate the flow of spent exhaust gases out of the combustion chamber during the exhaust stroke. By coordinating the timing of valve openings and closings, the valvetrain ensures efficient combustion and optimal engine performance.
Types of valve train
Different engines may utilize variations in valvetrain designs, such as an overhead valve (OHV), overhead camshaft (OHC), or dual overhead camshaft (DOHC) configurations.
Advanced technologies like variable valve timing (VVT) and variable valve lift (VVL) allow for even greater control over valve operation, optimizing engine performance across various operating conditions.
--- Time Stamp --
00:00 - Introduction
00:40 - Parts
04:16 - Types of Valvetrain
04:42 - Overhead Valve (OHV)
06:25 - Overhead Camshaft (OHC)
07:03 - Single Overhead Camshaft (SOHC)
08:38 - Dual Overhead Camshaft (DOHC)
11:07 - Flathead Engine
16:39 - Thanks For Watching
#ohv #sohc #dohc
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Disclaimer:
This video is just for educational purposes only. We are not in the auto repair business nor publish automotive service manuals. This video is not reviewed or authorized by any vehicle manufacturer. This video is intended only as general guidance. Every system is slightly different, so refer to the owner’s manual of your vehicle for any specific information about your model. Remember that only proper service and repair procedures will ensure your car's safe and reliable operation.
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Worth mentioning that flat head designs were still very common in small engines until recently. (Such as in lawn mowers and generators)
And I don't miss them one bit! I went from a 4 hp. side valve Briggs and Stratten powered lawn mower to a 5hp Honda OHV and I couldn't believe the difference. The Honda uses about half the fuel and, to the nose, emits about half of the unburnt petrol. That said, I'd rather a '32 Ford V8 was sitting in my driveway than my Civic!
@@davidbrayshaw3529 Actually it took Ford a year to sort out the V8 Flathead motor. Very few 32's with original motors.
Soviet T-34 tank. all aluminum V-12 DOHC diesel 4v per cyl, shaft driven valve train 85 years ago
The video says this at 11:25
There's a new light aviation flathead engine (d-motor). Air engines run at low rpm's (max 2500) so that's not an issue. The compact engine without the valve gear on top of the opposed cylinders is good aerodynamically. And the overall weight is a bit reduced.
@2:07 valve springs do not exert downward pressure on valves, they exert upward pressure on them, which is how they are closed.
Nope. The springs exert downward pressure. Down is not relative to earth and sky. But relative to the valve seat. Down is with the valve seated (closed). For instance, a lawnmower engine with a vertical crankshaft and horizontal stroke. The valves move (open and close) horizontally also. What is "down"? Down is valve closed. Thus, the spring exerts downward pressure on the valves.
Thats what he said. But he forgot to mention the camshaft
Valve springs only close the valves, that's it. Desomodromic valve train that's a different story
This video helped explain to my son what is going on with my truck.
One type you missed is the "F"-head, where the inlet valve is push-rod operated in the head and the exhaust valve is [as a side valve engine] in the block. This allows for two things. Smooth power and a huge inlet valve for good breathing. They were used by Rolls Royce and Rover from the early 1945 era until the late fifties in Royces, and right into the 1970s in Land Rovers. They are famously quiet, smooth [especially in in line six form], and robust. Neither Royce nor Rover really made performance cars, but they did build cars to last and be comfortable. Several Bentley variants of the Royces appeared that showed that such an engine could really perform in the grand tourer segment of the luxury are market, such as the Bentley Mark Six and the earlier Continentals, before Royce's own new V8 was adopted across the Royce and Bentley models. Nice video. Thanks from George [in UK].
A "Flathead" with a correctly sized turbo would be ideal.
don't forget the Atmospheric IOE.....hey, it worked anyhow...
I've never worked on such an engine but from what I heard the were somewhat inefficient and not as reliable as they wanted it to be hence why it did not catch on.
Hi George, in the late 70's my brother had a Land Rover with that style engine. At 90mph, the 'aerodynamics worse than a house brick' meant the door tops got sucked out about an inch. You could also watch the fuel gauge dropping like the second hand of a watch! Video also missed out on Ducati with desmodromic valve operation (I don't think anyone else uses it?) The head shown around 7 minutes looks like a Triumph Dolomite, direct operation bucket one side and rocker for the other?
Kaiser/Jeep used a F head design in the mid 50's the 134CID engine and the 161CID engine.
Overhead Valve design does not automatically mean more low end, rather OHC allows higher revs with lighter valve springs due to the lighter valvetrain. Camming an engine for higher revs takes away low RPM torque. That is the reason Overhead engines tend to have more low end- OHC engines tend to have aggressive camshafts and therefore have weak low end.
Thats not the reason at all
@@wiktorjachyra1869 Ok, I will say it differently then: Pushrod overhead valve engines do not have more low end torque than OHC engines just because they are pushrod engines, but rather OHC engines have a light-weight valve train that allows the use of relatively soft valve springs. so those engines can use a more aggressive cam shaft without having to resort to the super-stiff valve springs that a push rod engine would require. That more aggressive cam shaft means less low end torque but more high end horsepower, and the fact that it doesn't need super-stiff valve springs also means less internal friction and freer-revving characteristics. This assumes everything else being equal.
You're right. NASCAR uses ohv engines and they rev over 9k rpm.
Why does the 2020 Corvette make 30 hp more than the 2019 Corvette?
@@Tom-xd4ct In contrast, the Merlin engine in Spitfires during WW2 was a SOHC 4-valve per cylinder unit V-12. Peak power was at a mere 3,000 rpm.
Triumph had a lovely Sprint engine that was 16 valve straight 4 engine. One cam, with one set of valves under it and the other side working off rockers but on the same cam! It was a lovely neat design that kept the engine quite compact. I always wondered why this configuration was never used more.
I wonder too.
Sounds like the Alfa Romeo "Busso" V6 ("Busso" is the italian word for "Bullshit"): - In 2.0TB it's quite a pointless design, really.. derivating from 4v/cyl. where they made 2v/cyl version - but still on twin-row, cross-flow valve-design: - The intake valve is driven, directly by the cam, with a rotating cup (tapper). I see some logic here.. Not the best, but quite simple. Classic design. Me - okay here. - For the exhaust - the cam's profile is offsetted on 90 deg. next to the intake - because the movement is picked up by a horisontal tapper - then, a push-rod - which drives the rocker; - the rocker, itself - hinges on a rocker-axle which is placed, where the exhaust-cam would stay if it was 4v/cyl. (WHY?! Why not go JUST with a second cam? Who does that!? And if "Nobody" - why?!?!) On the other side of the rocker is the adjustment screw for valve-clearance, and this drives the exhaust valve.. :D How stupid is that?!? - twice more complex design, with 3-4 more weakpoints, heavier - in order to LOSE power! Not like the 24v was something impressive, but 12v - blew my buttcrack, really. This is simply - combining weaknesses of DOHC's & OHV's. With none of the profits. (Let's say it's an Alfa-thing)
Yes the dolly sprint engine was the first mass produced 4 valve per cylinder engine.
@@grebo121 I had an Alfa 33 for many years, it ran like a train doing 200+ kph from a 1.6 litre engine, problemfree for more than 300.000 km. Lovely little car.
honda d series and mitsubishi 4g92 has also 16V sohc, very compact but still allowing high performance for its size
The valves in an Overhead Valve engine are not in the block, they are in the head. Flathead engines have the valves in the block.
You got that right. Even the diagram they used pictures the valves in the head.
Ohv engine are also known as cam in block engine.
Dohc sohc ohv
OHV engines are ideal in countries that dont tax displacement. They make most of their power in usable revs, are light, compact, very fuel efficient and have very low service costs. The only drawback is that you need to give them a bit more displacement. The market needs another Buick 3800 V6. That engine made the same power (205HP) as most 3.0L DOHC V6s of its time, was smaller, lighter and got 31MPG highway moving large cars around the highway and are extremely reliable. I had a 2005 Mazda 6 and that car was smaller than something like a Pontiac Bonneville and only got 29 highway from a 2.3L DOHC 4 making 160HP.
Definitely agree the family of engines is great and easy to work on
Some single camshaft engines had the cams directly mounted over the tops of the inlet and exhaust valve’s leaving space for spark plug; for example the Coventry Climax racing engine which was also used in Hillman Imps and fire engine portable water pumps.
DOHC does not imply 4 valves per cylinder, although it makes it easier. There are many DOHC engines with 2 or 3 valves per cylinder (for instance the classic Alfa Romeo engines) and there are also 4 valve per cylinder designs with only 1 camshaft (such as the Triumph Dolomite Sprint, as someone else mentions). The main advantages of DOHC are certain kind of simplicity and lightness of the moving parts + ability to regulate the position of the both camshafts individually when you are going for adjustable timing arrangements.
In what timing situation would you want the valves opening up unsynchronized on the 2 cylinder banks?
Very comprehensive and clearly explained. Thanks!
It sounds and looks great. Thanks for your efforts
Excellent, well presented and very educational. Thank You and Best Regards.
Based on my long long experience, OHV , is the best valve -train design. Period. Thanks
It's good in tractors.
Said no one ever!
The Renault 16TS had an OHV engine and dominated many races at the time
Must be true as you used ' period '.
Just subscribed excellent video packed with historical and useful information. Thanks for sharing. 👍
Amazing video. Good pictures as well as good explanations of advantages and disadvantages as well as history. Perfect
What an easy explanation... The best ever video i have seen ever😊
OHV / center cam. Used for decades and time tested.
Over head cam is even older.
It’s ok for small application, terrible for high horsepower
Very useful. Thanks for sharing
I always thought OHV naming instead of calling it pushrod was a 80s way improving pushrod's PR problem during the Japanese flood of overhead cam and DOHC offerings. After all, they all have valves up top.
now i understand so much of valve train i mean those pictures tells you everything
".....Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead?....." Depends upon the application, the budget, and the fuel.
Terima kasih telah berbagi ilmu, smoga bermanfaat.
All things being equal, rpm determines power. The higher you can rev, the more juice you get. Obviously DOHC engines are best for high-end power. I stipulate that Chevy has done a fine fine making their ancient OHV designs perform well.
This is true. For the mundane duties we perform every day, the OHV 2 valve engines work just fine, plus it's smaller, lighter, and cheaper than an OHC engine. So many people believe they need a DOHC engine with VVT, V-Tech, and all the other fancy crap when all they do is sit in traffic on their way to work. I do love my Toyota V8, but I dread the day something goes wrong. An old Vortec or LS is a much more user-friendly engine.
My 89 Mazda 323 has the very reliable B6 series engine. It has a single overhead cam and 8 valves. The peak torque comes low at 2500rpm and you feel it. High end power is low however and you feel that also. It behaves more like an OHV motor.
GM engine X16SZ is same.
Super! Thank you so much for it.
The Honda CX500/CX650 and various diesel engines use pushrods and 4 valves. Done correctly, this setup has the obvious advantages of each design.
Everything I Always Wanted to Know About Valves (But Were Afraid to Ask)!
I like the Detroit Diesel setup that has the cam gear driven just below the head, with the rollers mounted to the head. It gives all the advantages of OHC without the extra complication (labor cost) of dealing with chains and cams and all that when doing a head job. (EDIT: Talking about the 71/92 series, I don't know anything about the later model stuff)
Thanks a lot 4 the video, it's really very interesting.
There never is a best, always an engineering compromise. It is all about the initial design criteria.
I'd say that's incorrect. The overhead valve is much better in regards to efficiency than a flathead. The same goes for overhead cam vs cam in block, have more options for size of valves, number of valves, and chamber design, not to mention intake and exhaust port design and size. Dual vs single overhead design means you can more specifically tailor valve timing, geometry, and again number of valves per cylinder. You don't really want to control four valves per cylinder on one cam.
Weight and packaging are a determining factor. So you are wrong. Corvettes get the same gas mileage as Civics. How is that for your efficiency.
I agree, a compromise. Flathead is out of date, but has the advantage of liquid cooling the exhaust improving durability. Inlet over exhaust also has this benefit. OHV has a place in low Octane environments (as does the above ) OHC does make the most *of 87+ octane economically. But that wasn't always the case with gasoline. DOHC is great for high Octane fuel, 89+
@@drtracernum20 I think their point is that if you have limited space, you may need an OHV design to maximize the available room. Likewise for reliability, required maintenance, etc.
Flexibility is best. Variable intake, variable timing, variable compression, variable displacement. Direct injection is best til the intake gets carboned up. Turbo beats supercharger though. C4s made 250-275 horses until DOHC LT5 came out. 50% more power, 200% the price for the car. Chevy should've stuck it out with that setup and learned to build the engines themselves. Develop improvements along the way. The ZR-1 was the only interesting C4.
OHV 😊 I just love chains, belts, and tensioners that fail causing massive damage when the piston repeatedly smashes into the valves 😈
The combustion chambers in a flathead are in the head. It is the valves that are in the block.
🎉Enjoyed a lot . Thanks.
Thank you so much for teaching
Love these videos!
Great video. I learned.
Awesome video, thanks.
Great appreciation👏
The answer to the question in the title depends on whether best actually means in terms of power, torque, speed, or reliability or durability, or all. My considered opinion, and taking life experiences into consideration; If the quality of materials for all designs are high and equal for all configurations, of course the dual overhead cam gives the highest volumetric efficiency, power and speed, especially if more than two valves per cylinder are present. That said, the drive linkage for the multiple cam shafts is more complicated than the other designs, with many more moving parts , and can be prone to more instances of wear and catastrophic failure. As for reliability and durability, the flat head valve train is the simplest, and least prone to failure, with no rocker arms, or push rods and either a gear or chain drive for the camshaft. Bottom line for the flat head is that the design is dependable, but efficiency is not very good compared to the others partly because the fuel/air mixture has to be lifted up, against gravity, into the combustion chamber. To me, the push rod, overhead valve, and single overhead cam engines, strike a happy medium between the two extremes I have referred to, with reliability and efficiency both taken into account. I will add that any interference engine, with a fabric timing belt, is asking for catastrophic trouble, I don't care how efficient and powerful it is.
Thank you for posting this. It was very effective in communicating the differences in the configurations.
Push rod OHV for me please.
Thanks alot man.
What about desmodromic valve systems? Used mainly by Ducati, but I assume by others.
I think an interesting topic would be discussing Coates spherical rotary valves. They're simple and efficient
And with the doubling of the power output from the Coates heads negates the use of forced induction set ups. And for the low end pockets that most of us have, Rhoades lifters does away with trying to pay for roller rockers
@@jamesharrison6201Exactly. Keeping things mechanical while improving overall performance and efficiency
Very nice
good video. thank you.
Judging by the simplicity, reliability and superior power output of the Chevrolet LS pushrod engine compared to the double overhead cam Ford stuff, I say you have your answer.
Very good info
If the flathead valve it's in the cylinder, how is the carburetor or injectors works and how can you mount it in the cylinder which is close to the crank shaft
I have been studying Diesel & Petrol Engines or Fuel Injector Engines & Spark Plug Engines for 15 Years now and will continue to Automobile Engines also.Studies are way ahead....Still studying to Master the Application on Engines..Anthony Anakapu.
Bro honestly no one gives a fuck
15 years is almost half the career time of an engineer in any profession.
Many thanks...
Amazing😊👍
To jsou takzvané spodové motory, kde jsou ventily vedle válce ovládané spodem od vačky.🤔🤩
What is the engine designed to do? What RPM range is it expected to operate in. Lower RPM OHV is perfectly acceptable. High output low displacement. DOHC w/4 valves per cylinder.
Thanks
A fantastic video with one error. At 11:12 the labels for the graphics are mismatched. The OHC label should be on the left, and the OHV label should be on the right.
@the engineers post do you have pdf for this.
I think reliability n efficiency durability is best for everyone to transport from work family travel n people that are not mechanically incline, it would be best for the world to all ideas to built that one engine , even old inventions work , as a realist
It depends for longevity go with KISS ! Which would be over head valves with push rods. Fewer moving parts.
I want to know more about the other types of valves. sleaved and rotary
Define the parameters of "best". The context and especially the timeline plays a major part, thus the question is as ill-defined as when asking which snake is the biggest. Considering length or weight?
3:07 you had OHV & OHC back to front!
That's right, he labeled the OHC diagram as OHV, and the OHV diagram as OHC. It's been two weeks since he uploaded the video, I wonder if he is aware of the error. I hope he reads these comments and will make the necessary correction. Otherwise it's a decent educational video for newbies.
I came here to say that too. Wanted to see if anyone else noticed that.
I noticed that too. Had to back it up to make I saw what I thought I saw.
The best is the SIMPLEST with the fewest parts to get the job done with REASONABLE economy, power and cost to build. If you have looked at the valve trains of modern engines you can see why they cost so much to fix and have spectacular failures. No need to get 500+ HP out of engines. You aren't running at Indy.
My honda CX500 was a V twin with 4 valve heads. The heads are just behind the riders' knees, but heres where it gets weird. The heads are twisted by 22 degrees so the carburettors are tucked in and exhausts splay out. This cant use an overhead cam so its pushrod. Each pushrod works a rocker that opens two valves. There are lower finger followers too. Mine was nicknamed "The Knocker" by my friends as all this valve gear makes a racket. 4valve OHV. A picture tells a thousand words. Look up a Honda CX500.
Which is the Best Engine Valvetrain Design? OHV, SOHC, DOHC or Flathead | Pros and Cons
Actually the 'Desmodromic' valve design is the best.
pushrod v8 lowend rumble is music to my ears..
Great 🎉
Because of you guys i know everything about V6 engine and combustion engine how it's work. Thanks for you guys
OHV owner here. :D
Push Rod Engines are the most practical engines. BMW Boxer Oil Head 4 Valve Engines used in R1100, 1150 & 1200 RT & GS are good examples.
You are so correct. Working on push rod engines is so much less hassle.
I like the high revving Japanese engines so timing chain for life🎉❤
The "oil-head" boxer twins from BMW are technically "in-head cam" engines (with very short pushrods). The oil-head engines have two camshafts (one in each head), unlike the older "air head" engines that had only one (centrally located) camshaft.
Desmo system of Ducati?
I love thisi
GM has proven with the LS engine you can have an old fashioned OHV cam in block and still keep up with and exceed the other guys with any other valve system. To say it limits performance is BS, and it's less complicated to less parts to break.
You just need large displacement cylinders to compete.
@@billymania11 OHV 520cc singgle cylinder can produce 33 HP, seem win win for me, actualy for motorbike that need bigger CC, but still love fuel economy and high low torq and small gear usage with CVT, it's would be just fine, cause actualy CVT make torq more exist with OVH engine set up,
Rica etsem altyazı seçeneklerine Türkçe dil seçeneği ekleyebilir misiniz ? Sizi anlamak ve takip etmek istiyorum !!!
altyazı ayarlarına gitmeyi denesen görürsün
The video was really helpful visually but the clicking and typing sound effects were distracting for listening.
Overhead valves,easiest to work on.The dohc and sohc,a pain in the ass to time and work on
There’s no question about the overhead valve. Much lower center of gravity, lighter engine, and infinitely simpler, and the parts that typically fail on dual overhead cams and such as chains and chains guides are eliminated.
I graduated from university with a degree in mechanical engineering. I think that the age of electric vehicles is coming, but I think that conventional internal combustion engine vehicles are the best materials for learning mechanical engineering.
Electric won't be for the masses for at least another decade. Even then it will take several more decades to attrit current ICE from common use. There may also be hydrogen ICE etc.
Did you or were you required to take any classes in electrical and/or computer engineering ?
The problem with electric cars is they are luxuries and very expensive to buy. Like everytime an automaker showcases one is fully luxuries and not making a practical model. So far the ford lighting and mach e are the practical electric vehicles with "ok prices" unless if I missed other brands. This is where automakers should start instead of throwing high end editions.
OHV is the best when working on a engine.
OHV is the best as there is no belt or chain that can break causing seriously expensive damage to the engine. After all radial piston aviation engines use OHV and push rods.
FYI: virtually all automotive pushrod (i.e. OHV) engines have cam timing chains (or belts)
Radials use pushrods because it's impractical to use overhead cams on them at all (you'd need a camshaft for every cylinder. Try that on an 18 cylinder radial!). Water cooled inline aircraft engines usually used overhead cams. E.g. Rolls Royce Merlin was SOHC.
@@danielklopp7007pushrod is typically used today by lower rpm diesel engines (since they have an RPM limit) like commercial truck engines. These use gears to drive the camshaft. In Europe push rod does not exist in car engines, not even 50 years ago
You can get 4 valves per cylinder in a sohc.
You can add turbo to flathead engine to increase compression 😄
A blower does not increase compression, it greatly increases breathing.
Obojí, kompresní tlak vlivem většího množství směsi 🤔🤩
Back in the day, you could get a set of Denver heads for the flathead fords because they were machined for more compression
The Flat head was more of FORD able!
It would make more sense if the flathead valvetrain was explained first.
Muito bom.
"none of the above" is the right answer... Koeneggsegg's "Frevalve" is a far superior design
You are a very good KZheadr. ❤
Can you make a video, Some Manufacturers says 24.31PS@6500RPM & Some says 43.5PS@9000RPM and 32Nm@4000-4500RPM & 35Nm@7000RPM. Can you explain or make a video please.
We use Brake Horsepower @RPM, and Lbs. Ft. of torque @RPM.
@@michaelbenardo5695 ... I think you meant to say, "In the United States, we use...". Germany historically used PS as a measure of power. Most of the rest of the world now lists engine power in KW (KiloWatts). Here are the conversion: 1 BHP = 1.014 PS; 1 BHP = 0.746 KW. BHP, PS and KW are all valid measures of power, just using different units.
For some slow speed applications an L head (valve in block) is a better option. The old flat head Ford 8N tractor can, in some cases, out work it's modern cousins. Outwork here is defined as plowing more acres with the same sized plow on less fuel burned.
A flathead, with it's simple light weight valvetrain, has less internal friction, everything else being the same. That gives it an edge in mechanical efficiency.
What about free valve or camless engine?
Free valve has not been in mass production yet. It is a vapourware. It is good for billionaire who drives their hypercar as toy and does not rack up mileage. There is a China car manufacturer that has licensed the Freevalve tech. They make a prototype to demonstrate in a China carshow. Nothing heard since there. They silently drop the project. Thus Freevalve is not the real deal. If you have billion, you can ask fancy hypercar maker to make you one. That's it.
Opposed piston engine ?
Go opposed piston 2 stroke & get rid of all the excess .
2 stroke Diesel only though... Never heard of a petrol/ gasoline version entering service.
@@android584Lawn mowers are 2 stroke.
I support opposed piston 2 stroke.
@@angelgjr1999 I don't think there are any 2-stroke lawn mowers available today.
sleeve valve engine?
You forgot desmodromic valve trains. See Ducati motorcycles. The system increases hp by reducing valve train resistance. There are no valve springs in a desmo head.
The other advantage to desmodromic valve actuation is a (theoretically) higher red-line. That said, pneumatic valve springs (as used in all other MotoGP engines other than Ducati's) eliminate the higher red-line advantage (but pneumatic valve springs are impractical for production engines).
Para mi OHV, es el sistema más duradero.
"Pushrod engines are old tech, they suck!" Laughs is LS... 🤣
Thank 💡💡💡💡💗💗😎😎👍👍🎈🎈
What about a boxer engine like Subaru ?
What about them?