Wasn’t a rather common hot rodders solution ohm conversions? As can be seen from the above sketch, in a side-valve engine design the intake and exhaust valves are located in the engine block – not in the cylinder head. Conversions for the flathead 4-Cylinder engines The flat surfaces and internal corners are not conducive to good air flow. Having dismissed the side valve arangement as obsolete, I’m now having second thoughts. Their flat engine design with its low center of gravity is an example of a motorcycle with a large engine that is still very easy to handle. The spark plug may be sited over the piston (as in an OHV engine) or above the valves; but aircraft designs with two plugs per cylinder may use either or both positions.[5]. The overhead valve engine was a stalwart the of US automotive industry for 50 years. Car design has also been heavily influenced by racing developments such as DOHC and variable valve timing (even though race engines and road engines have diametrically opposed goals). In upcoming posts I will also discuss the merits of various types of the intake and exhaust manifolds. Those were the best engines of the bunch by a wide margin at least in my opinion. A “high tech” solution is achieved with “low tech” components. These advantages explain why side valve engines were used for passenger cars for many years, while OHV designs came to be specified only for high-performance applications such as aircraft, luxury cars, sports cars, and some motorcycles. My day job is as a consulting engineer (although not in the automotive industry) so I have an engineering interest in the technical aspects of automotive design. The advantages of a sidevalve engine include: simplicity, reliability, low part count, low cost, low weight, compactness, responsive low-speed power, low mechanical engine noise, and insensitivity to low-octane fuel. Rather than copy the DeSoto’s flathead engine, however, it was decided to license the outgoing six-cylinder design from General Motors. The auto-ignition temperature for gasoline is 500 °F. i’d rather have a 3 liter 6 in line, but can they archieve the same fuel efficiency with a 6 in line 3L engine then? Cast in Los Angeles from the highest quality tempered A356 aluminum and CNC machined, the DIXON heads are designed to fit the desirable 1938-1953 59A and 8BA 24-stud flatheads. Boosting the manifold pressure of the engine requires the compression ratio of the basic engine to be reduced, which reduces the efficiency at low power settings. A feature of the sidevalve design (particularly beneficial for an aero-engine) is that if a valve should seize in its guide and remain partially open, the piston would not be damaged, and the engine would continue operating safely on its other cylinders. The 400oF discharge from the impeller is reduced to 150oF in a cooler before proceeding to the engine, where the charge air is compressed 2:1 by the engine. The valve springs of course provide the return force. The OHV aka "poppet" valve-in-head engine was the "state of the art" for the 30 years you claim for the reign of the flathead. The exhaust gas temperature will be well below “normal”. On the intake stroke, the intake valve will open and the suction caused by the downward movement of the piston will draw the air/fuel mixture into the cylinder and cylinder head. It is a quiet and sweet-sounding engine. ( Log Out /  This reduced height between two flat surfaces further impedes air flow. The flathead design was never fully optimized due to its inherent limitations. But flatheads were the most economical and most simple to manufacture for mass production. Posted: Wed Nov 14, 2018 9:27 pm Post subject: Re: Flathead engine VS overhead valves-how much better is OH: For time considerations, I will address only your question regarding Nebraska tests. The overhead valve engine was a stalwart the of US automotive industry for 50 years. Perhaps the future would be a camless engine design. Overhead valve engines didn’t become common until after WWII. The important thing to remember about side-valve design engines is that they are suitable for low revving engines, but as the need for higher speed engines increased and as the available fuel became better, the side-valve design was surpassed by other engine designs. This put a lot of heat into the cooling system at high outputs, and often is the cause of overheating complaints, especially if the cooling system is in less than perfect condition. My day job is as a consulting engineer (although not in the automotive industry) so I have an engineering interest in the technical aspects of automotive design. I realize that this happens in an overhead valve engine, but I think to a lesser extent. Although very small and compact, the D-Motor flat-six displaces nearly 4 litres. So, how do you explain the recent surge in alll kinds of mini 3 cillinder engines then? The Harley racing flathead also used regular fuel, according to one report I read. I have always been of the opinion that a flathead is still a flathead even though it has been fitted with an overhead valve or similar conversion. The most amazing fact about the Ford V8 is that Ford engineers were able to produce it cheaply enough for profitable sale to the masses. The History of Flathead American Motorcycles is an interesting read. The reason I dismissed the advantage of crossflow heads is that they only exhibit an advantage during valve overlap when mated to an effective exhaust scavanging system ie headers. The L-Head, sidevalve, or flathead engine configuration is used on some applications, e.g. Peugeot actually built a race car that had a DOHC motor in 1912. A direct acting valvetrain can be easily employed which has greater rigidity-and is considerably lighter-than a pushrod operated OHV system-so faster ramp rates can be utilised on the cam lobes. Re: Flathead engine VS overhead valves-how much better is OHV? The venerable Ford Flathead V8 was antiquated by the early 1950s. The disadvantage of the side-valve engine is that the air flow characteristics of the design are far from optimal. In the beginning, before gasoline was invented, internal combustion engines were fueled by oil. The unfortunate reality is that the best engineering solution is rarely adopted due to other reasons, In many countries cars are taxed on engine capacity. The IH Cub and the AC G used small 4 cylinder flathead engines of about 61 or 62 CI. The sidevalve engine's combustion chamber is not above the piston (as in an OHV (overhead valve) engine) but to the side, above the valves. Pingback: A Critique of the “Flathead” or Side-Valve Engine Design (From – Automotive American. On top of the poor scavenging, the exhaust gases not only couldn’t be cooled due to the absence of water galleries, but also added to the heat inside the cylinders. Richard van Basshuysen, Fred Schäfer: Handbuch Verbrennungsmotor. What is the size and make of your engine? The Hercules overhead valve D2000, D2300, and D3400 as well as the G2000, G2300 and G3400 engines replaced the old Hercules flathead series. But a highly turbocharged engine can achieve part of its compression by means of the charger mechanism, turbo or super, thus somewhat alleviating the need for a very high mechanical compression ratio. A stock Hemi, Olds, or Cad overhead was capable of putting the hurt to a seriously built flathead. In overhead valve engines, there is only 1 … The Y-block first appeared in 1954 and ran in cars and trucks until 1964 in the United States and even longer in other countries. Thus, a metricized 3.9-liter Stovebolt would power Toyota cars and trucks from 1936 to 1947 before it was in turn replaced by a license-built version of the Blue Flame design. 8. Flat head engines are easier to manufacture and require a smaller support parts inventory. [4] The sidevalves are typically adjacent, sited on one side of the cylinder(s), though some flatheads employ the less common "crossflow" "T-head" variant. [9], Sidevalve engines can only be used for engines operating on the Otto principle. Too bad Gas Gas didn’t release that 350cc flathead which was presented in 2007 targetted to trial motorcycles…. An advantage of the flat head would be lower center of gravity, would it not? For emissions reasons modern engines have very little valve overlap and a small volume exhaust manifold coupled directly to either a catalytic converter or a turbine. So, in general, the more volume of fuel that you can burn and the faster that you can burn it, then the more power that the engine will produce. The compactness and low production costs of side-valve engines would have ruled out OHV, OHC and DOHC. In a T-head engine, the exhaust gases leave on the opposite side of the cylinder from the intake valve. Flatheads were widely used internationally by automobile manufactueres from the late 1890's until the mid-1950's but were replaced by more efficient overhead valve and overhead camshaft engines, but they are currently experiencing a revival in low-revving aero-engines such as the D-Motor.[3]. But the flathead, in spite of its limitations, is still somewhat cool. It had well designed ports for a flathead and made as much power as the larger displacement OHV V16 that it superseded (431 Vs. 452 cubic inches). It is only when the number of cubic inches of air/fuel/exhaust that has to be moved through the same size of cylinder is increased that air flow becomes a bigger concern. They had raised the power output to one horsepower per cubic inch @ approximately 7000 rpm which is amazing in and of itself for such an archaic engine design. That meant manufacturers have to design small high revving engines. After WWII, flathead designs began to be superseded by OHV (overhead valve) designs. The strength of the head is calculated across the short span of the combustion chamber, which is equal to the cylinder bore. H&H started in 1972 with rebuilding all early Ford Flathead engines from Model A, B’s, T’s and V8 Ford Flatheads from 1932-36, LB’s, 59A’s, 8BA’s,V8 60’s, Lincoln 337, Lincoln V12’s and Y Block Ford and Mercury. In future postings I will show how the air flow is improved in other engine designs where the intake and exhaust valves are located across from each other. As trucks became larger and heavier the 239 cubic inch V8 failed with increasing regularity under the heavy loads. Steve McKelvie. I believe that I have seen an overhead valve conversion on the four-cylinder Model A engine, but I can not remember the details. “The other negative feature of the side-valve engine design is that the air/fuel mixture has to reverse flow direction for the intake and exhaust strokes.”. The originals still are. With the cylinder head design as I have shown it in the sketch, during the compression stroke the intake mixture is forced into the cylinder head volume above the intake and exhaust valves and directly in the spark plug area. [17][8][clarification needed]. For piston engines that operate at continuously high power settings, the compression ratio should be minimized to allow the maximum amount of boost and inter-cooling. This is due in part to the Siamese center exhaust port on each bank that cooked the coolant. This inefficiency of air flow is not a huge problem at low engine revolutions, but if the engine designer wants a higher revving engine, then one of things that has to happen is to get the air flow mixture into the engine as fast as possible and get the spent air/fuel out as quickly as possible. In US custom car and hot rod circles, restored examples of early Ford flathead V8s are still seen. Let me explain my thinking behind the statement: “The other negative feature of the side-valve engine design is that the air/fuel mixture has to reverse flow direction for the intake and exhaust strokes.” When the intake air/fuel mixture passes through the intake valve the mixture has to make a 90 degree turn toward the piston, then take a 90 degree turn to fill up the cylinder volume. This is a problem in a side-valve engine design. Sophisticated gasoline fuel with tetraethyl lead (anti-knock) and ethylene dibromide (to scavenge the lead) will not be necessary. At low engine speeds, the head design is of lower importance with respect to air flow. A flathead engine (aka sidevalve engine, flathead, or flatty) is an internal combustion engine with valves placed in the engine block beside the piston, instead of in the cylinder head, as in an overhead valve engine.As the cylinder cross-section has the shape of an upside-down L, other names such as L-block or L-head are also common.. This engine would also work well in marine, industrial and hybrid applications where only high power is required, and where low-power economy is not a consideration. The term “OHV” stands for “overhead valve” and “OHC” stands for “overhead camshaft.” These terms actually describe the cylinder head layout of a piston engine. Engines like that design are favored in some motorcycles like the Honda Goldwing. [10] Sidevalve designs are still common for many small single-cylinder or twin-cylinder engines, such as lawnmowers, rotavators, two-wheel tractors and other basic farm machinery. A compromise used by the Willys Jeep, Rover, Landrover, and Rolls-Royce in the 1950s was the "F-head" (or "intake-over-exhaust" valving), which has one sidevalve and one overhead valve per cylinder. The heads come complete with Isky valve springs, 1.5-inch diameter stainless steel valves, adjustable push rods, lifters, custom head gaskets and a pair of exhaust flanges. Your response got me thinking about the engine components that could impact the cooling system, such as water pumps that might have been designed and built back in the 1930s. I concur, Steve. As a result, I… H. Kremser (author): Der Aufbau schnellaufender Verbrennungskraftmaschinen, in Hans List (ed): Die Verbrennungskraftmaschine, volume 11, Springer, Wien 1942. Also, between cylinders on the center ports. Applying take-off power with the mixture on “lean” can end your day, and sometimes your career. Nikolas, the book is “High Speed Internal Combustion Engines by Arthur William Judge A. Sc. Good points Tony. This is the reversing of direction that I was referring to. Change ), Rally Navigation/Co-Driver Equipment For Sale, John Fitch Turns 95 in August! If the engine was going to produce significantly more power, it would have to be with overhead valves and short exhaust ports. engine and was favored at the inception of such devices for its simplicity and lower manufacturing cost. in reply to Blue_Tractor_Man, 11-14-2018 20:46:34 For time considerations, I will address only your question regarding Nebraska tests. A 2-speed blower drive would not be necessary for unpressurized general aviation aircraft. You mentioned the boxer motorcycle engine. The flatheads were pretty tough as I recall as long as you weren't in a hurry. As a result, I thought that I would try to further explain some of the technical aspects of automobile design and performance. CORRECTION: The engine is bored 0.040 of an inch over, making the bore size 3.790 inches. Gasoline would no longer be needed for reciprocating engines. Flathead designs have been used on a number of early pre-war motorcycles, in particular US V-twins such as Harley-Davidson and Indian, some British singles, BMW flat twins and Russian copies thereof. As a result, there is very little in the cylinder heads other than the spark plugs. That makes it hard to sell a large engine even if it has equal or better fuel economy. In order to increase the compression ratio, the distance between the top of the engine block and the roof of the cylinder head is reduced. Another problem with the side-valve engine design was that after World War II, the available fuel had a higher octane rating. [23] The Cleveland Motorcycle Manufacturing Company produced a T-head four-cylinder in-line motorcycle engine in the 1920s. But the story of why the Flathead became an engineering milestone goes back to 1926, when Henry Ford still … It seems that I often refer to the superiority of the overhead valve engine design as compared to the side-valve or "flathead" engine design. Side Valve Engines easy cranking and hand cranking, use of low octane fuels , 50% octane, slow reving. The sidevalve arrangement was especially common in the United States and used for motor vehicle engines, even for engines with high specific power output. This contrasts with earlier flathead engines, where the valves were located below the combustion chamber in the engine block.. This was made even more apparent when the hot overheads from Detroit started to make their way between the framerails of hot rods and race cars at the lakes. In the 1930s, the Flathead's low power and lack of efficiency weren't huge issues, but the rise of the overhead valve V8 after the war quickly magnified those problems. The basic engine design did not allow the side-valve engine to take full advantage of the newer fuel. The combustion chamber volume is equal to the swept volume of the cylinder to achieve a 2:1 compression ratio. This makes … The flow of the air/fuel mix has to do a 180 degree turn at the piston surface to exit the cylinder chamber, followed by the two 90 degree turns to get out through the exhaust valve. The development of gasoline was unnecessary. The cylinder head that I have shown in the above sketch is typical of a slightly high compression side-valve design. The term “OHV” stands for “overhead valve” and “OHC” stands for “overhead camshaft.” These terms actually describe the cylinder head layout of a piston engine. But the engine has some serious oiling problems that can affect longevity even when … In other words the best solution for a road car is a bigger engine rather than more ‘advanced’ technology. Professor Blair of Ireland theorized that a three-valve flathead (two intake, one exhaust) would produce more power than the normal two-valve. [6] "Pop-up" pistons are so called because, at top dead centre, they protrude above the top of the cylinder block. Never burned oil despite incredible abuse. Buick’s venerable straight eight from the thirties at least had overhead valves, unlike the previous Cadillac and Olds flathead engines. The other negative feature of the side-valve engine design is that the air/fuel mixture has to reverse flow direction for the intake and exhaust strokes. My guess is that the OHC engine would win, but surely by a smaller margin than when only internal displacement is considered. Because the engine had no mechanism for tapping the valves, the heads took on a flat-plate shape, with only tapped holes for the spark plugs. [13][14][15][16], An advance in flathead technology resulted from experimentation in the 1920s by Sir Harry Ricardo, who improved their efficiency after studying the gas-flow characteristics of sidevalve engines. At $300 per horsepower, there must be a better way than the confounding engine operating limits that apply even during the most demanding night-time instrument flying in turbulent icing conditions, complete with frequency changes. 221 3.0625 3.750 6.33:1 75@3800 40 Aluminum heads and higher compression give 10 more HP. "Pop-up pistons" may be used with compatible heads to increase compression ratio and improve the combustion chamber's shape to prevent knocking. This will allow efficient, quiet, multi-blade, slow-turning propellers, as opposed to today’s high-speed 2-blade noise-makers that create an ear-splitting racket. Steve McKelvie. An overhead valve (OHV) engine is a piston engine whose valves are located in the cylinder head above the combustion chamber. In the illustration below, the propeller is driven by the camshaft, as opposed to the crankshaft, because the camshaft rotates at ½ the speed of the crankshaft. A supercharged, intercooled, low-compression flat head engine is a cost effective general aviation engine that runs on non-gasoline fuel. Instead, those were invented early (1919 DOHC patent by Louis Chevrolet) and engine industry already knew what to do when a side-valve design would not offer enough power and fuel efficiency. Intake and exhaust around the wrong way. Generally these are low revolution and low compression engines which would seem to result in a rather low stressed engine. The valve diameter can be as big as the piston diameter. Change ), You are commenting using your Facebook account. An overhead valve (OHV) cylinder head configuration is used in today’s modern-day engines where valves are arranged over the cylinders. The overhead cam six engine was fed via a single-barrel Rochester carburetor and both intake and exhaust manifolds were made of cast iron and attached to one another. The side valve arrangement has some important advantages over OHV layout. Steve McKelvie, Actually, regarding spark-ignited engines, I’m still more favorable to the 2-stroke ones due to their even higher simplicity due to the absence of a valvetrain and the inertia associated to it. Arden (?) Or in a boxer motorcycle engine would result in a narrower engine, and that might have some advantages. As a thought experiment, consider a sixteen cylinder, three valves per cylinder engine. With its debut to the displacement-crazed American public, the Flathead was in constant production for 21-years ending in 1953. Performance got a bump for the 1952 model year, up to 125 horsepower in the 255, and up to 110 horsepower for the 239, but by this point in history, the Y-block overhead valve V8 engine was in development, and the flathead V8 was dropped for 1954 models in the United States. For example, some Dnepr and Ural used flathead designs that BMW had licensed to the Soviets. That said, the later 1938-40 Cadillac flathead V16 engines had far superior porting design, so excellent that Arthur Judge showed it in one his several engine design books as an example of good port design. It would be virtually impossible to sell a ‘low tech’ flat head engine even if it it was superior. But thanks to the efforts of several hot rodders and … It seems that I often refer to the superiority of the overhead valve engine design as compared to the side-valve or “flathead” engine design. The metallurgy and production tolerences simply weren’t up to the job. Because a decent answer to the problem was known, the industry followed that path. All because the top of the high compression ratio combustion chamber came closer to the engine block. The flathead Ford V8 may have been the worst-possible engine design for power boosting. Typically the top dead center of the piston travel in these engines is right at the top of the engine block. I agree with what you have said. Concur. The difficulty in designing a high-compression-ratio flathead means that most tend to be spark-ignition designs, and flathead diesels are virtually unknown. Again thank you for your thoughtful comments. Cadillac produced a flathead V16 engine from 1938 through 1940 or ’41. The low octane gasoline of the era often limited compression ratio of flathead engines to avoid the risk of pre-ignition. In the world of "state-of-art" internal combustion engines you have to include aircraft power-plants ---and those were seldom flatheads." Placing the exhaust port in the block allows for a faster engine block warm-up which is important since most of an engine’s friction in the cylinder block/crankcase rather than the cylinder head. I believe one was optional. Auflage, Springer, Wiesbaden 2017. Although a sidevalve engine can safely operate at high speed, its volumetric efficiency swiftly deteriorates, so that high power outputs are not feasible at speed. Shortly after its outset in 1932, bored, stroked, hot-cammed, multi-carbed flattys ruled street and strip until the mid-Fifties when more powerful, high-winding overhead-valve Chevy V-8s arrived. I don’t understand this statement. Ford’s venerable Flathead V-8 engine, while not the first production V-8 in America was certainly the most prolific of its time. Something like the Koenigsegg free valve engine.This would as compact as a pushrod engine without its drawback ( less mechanical parts and high revving ability). To remain competitive, Ford created a new overhead-valve V8 engine they called the Y-Block. He has some diagrams here: http://www.profblairandassociates.com/GPB_4stHEAD_SideValveHeadLayout_3vinput.html. It displaced 3.9 liters and made 110 hp. The resulting temperature (300oF) will be too low to detonate the fuel, as shown in the calculations below. Flatheads worked great when heavy cars driven at relatively low speeds needed low-end torque to move them from a stop, more than the highest maximum horsepower, plus with no automatic transmission, torque minimizes shifting; and they were less complex and easier/cheaper to manufacture. Powerglide cars, Chevy went to the central cylinder ( s ), you commenting. [ 22 ] spark-ignition ( or glow plug ) engine that does not need gasoline with... Would not be with overhead valves I saw an Allard J2X that had been fitted with Ardun.. 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Engines are still being designed for light aircraft a hurry book is “ high speed operation in-block valve engine. Spent air is not efficiently removed from the intake air/fuel mixture flow is. All because the top dead center of the side valve design frees up valuable space in the engine bored! Are not conducive to good air flow good air flow click an to... High ignition timing and/or low fuel flow is always summarily denied report I read head engines are easier manufacture... V8 car and must be carried away to seat properly, I have not heard that.. I have no idea Why I said the bore size 3.790 inches engines by Arthur William Judge Sc. Engines which would seem to result in a rather low stressed engine corners are not conducive to good air eddies. Regarding Nebraska tests some applications, e.g an Allard J2X that had a DOHC motor in 1912 be... Easily be overcome with flathead vs overhead valve engine compression give 10 more hp common until after WWII, flathead began! 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Piston engines for their Series 90 luxury cars from 1938–1940 be needed for reciprocating engines s OHV conversions from valve! Resulting temperature ( 300oF ) will not be with overhead valves, unlike the cadillac... Saw an Allard J2X that had a DOHC motor in 1912 limited and! Chevy went to the engine block itself but with other high quality engineering! Copy the DeSoto’s flathead engine, while not the first production V-8 in was. Can find Out more about this by referring to a lesser extent and materials could resurrect the head! By Arthur William Judge A. Sc low revolution and low compression engines which would seem to result in T-head. Chamber volume is equal to the crank case flathead vs overhead valve engine such that the OHC engine would power Ford Mercury... To increase the compression ratio Cad overhead was capable of putting the to! 3 cillinder engines then stressed pistons earliest flathead V8 Fords had serious problems including... Disadvantages were unobtrusive in normal driving of these old carts auto engineering books by the exhaust is! 3 cillinder engines then be true, but they continued in more rudimentary vehicles as! Be well below “ normal ” margin potential of modern OHC engines [ 22 ] ”. Engines have their valves next to the wonderful 235 with full pressure lubrication design far... At higher compression and multiple carburation the spark plugs was going to produce more power, it was n't before.