flathead vs overhead valve engine

In a T-head engine, the exhaust gases leave on the opposite side of the cylinder from the intake valve. The resulting temperature (300oF) will be too low to detonate the fuel, as shown in the calculations below. Wasn’t a rather common hot rodders solution ohm conversions? The strength of the head is calculated across the short span of the combustion chamber, which is equal to the cylinder bore. [11], The flathead's elongated combustion chamber is prone to preignition (or "knocking") if compression ratio is increased, but improvements such as laser ignition or microwave enhanced ignition might help prevent knocking. A flathead engine, otherwise sidevalve engine, is an internal combustion engine with its poppet valves contained within the engine block, instead of in the cylinder head, as in an overhead valve engine. ( Log Out /  hopefully (fingers crossed) i won’t need to replace my flathead anytime soon. 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. Noone has mentioned his squish head design that revolutionized side valve engines. lawnmowers and motorcycles but nowadays is rarely seen in automobiles. OHV. https://youtu.be/S9E2nCXNHU8EE Shirts! In terms of flow there’s little real benefit to the crossflow arrangement. Diesel engines are economical in automotive applications because a direct injected diesel has no throttle and runs at full manifold pressure even at idle power. Name me ONE new car engine between 1922 and 1949 with overhead valves. 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. [9], Sidevalve engines can only be used for engines operating on the Otto principle. As a result, I… 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. In other words the best solution for a road car is a bigger engine rather than more ‘advanced’ technology. You’re right, Mick, that the Ford V* exhausts through the block. Many side-valve engines do not have this clearance reduction and the roof of the cylinder head is at a common distance all across the cylinder head which reduces the compression of the air/fuel mixture compared to what I have shown. 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. 221 3.0625 3.750 6.33:1 75@3800 40 Aluminum heads and higher compression give 10 more HP. The flat surfaces and internal corners are not conducive to good air flow. [8] Because sidevalve engines do not burn the fuel efficiently, they suffer from high hydrocarbon emissions. The main disadvantages of a sidevalve engine are poor gas flow, poor combustion chamber shape, and low compression ratio, all of which result in a low-revving engine with low power output[7] and low efficiency. 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. Those were the best engines of the bunch by a wide margin at least in my opinion. The originals still are. There was a time when Ardun overhead-valve cylinder heads were incredibly rare. Intake and exhaust around the wrong way. Engineers during the flathead era had limited research and development tools and getting reliability was often a challenge. If the compression & breathing problems of side-valve engines had been overcome some other way than with overhead valve systems, then even modern piston engines would still be some side-valve design. Because a decent answer to the problem was known, the industry followed that path. In other words it was a lot easier for the OHV engines to reach the 45 horsepower mark than it was for the flatheads at the time. Change ), You are commenting using your Google account. 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. In the world of "state-of-art" internal combustion engines you have to include aircraft power-plants ---and those were seldom flatheads." 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. But the flathead, in spite of its limitations, is still somewhat cool. It would have 48 valves which would go some distance to reducing the power margin potential of modern OHC engines. The combustion chamber volume is equal to the swept volume of the cylinder to achieve a 2:1 compression ratio. The compression ratio was 3:1 to prevent the heat of compression from detonating the oil. [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. Once seldom used in gasoline engines due to high temperatures, it is now beginning to be used in high priced sports cars. Thanks for taking the time to reply. Chrysler didn't go to an overhead valve engine until 1960. 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). Thus the flathead V-8's tenure came to end. During the 1950’s Harley Davidson engineers had “perfected” their design of the 45 cubic inch (750 cc) flathead engine for the AMA racing series. The flatheads were pretty tough as I recall as long as you weren't in a hurry. The supercharger would be packaged as a close-coupled unit with an 8:1 step-up gear drive. I always wondered if modern ideas and materials could resurrect the flat head. The Ford Flathead V8 was the first mass-market V8 and the starting point for uniquely American performance. Contents. Oddly enough, the first of the new-era 1955 Chevrolet OHV V8 engines had the same problem, plus the longer term issue of no oil filter. The IH Cub and the AC G used small 4 cylinder flathead engines of about 61 or 62 CI. 8. In my sketch above, it can be seen that the air/fuel mixture moves from right to left during the intake stroke and from left to right during the exhaust stroke. I believe one was optional. The greater percentage of compression ratio that is developed in the supercharger, and the lesser compression that is developed by the reciprocating expander, the more efficient is the engine package at sustained high power settings. Two modern flatheads are the Belgian D-Motor flat-fours and flat-sixes. The compact nature of the side valve design frees up valuable space in the engine bay. The early history of hot rodding was built on the back of the Ford Flathead V8. OHV vs OHC. Or in a boxer motorcycle engine would result in a narrower engine, and that might have some advantages. The venerable Ford Flathead V8 was antiquated by the early 1950s. 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. [6] "Pop-up" pistons are so called because, at top dead centre, they protrude above the top of the cylinder block. europe is flooded by small 3 cilinder designs lately. Change ), Rally Navigation/Co-Driver Equipment For Sale, John Fitch Turns 95 in August! An overhead valve (OHV) cylinder head configuration is used in today’s modern-day engines where valves are arranged over the cylinders. [1][19], The simplicity, lightness, compactness and reliability might seem ideal for an aero-engine, but because of their low efficiency, early flathead engines were deemed unsuitable. Peugeot actually built a race car that had a DOHC motor in 1912. 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 Harley racing flathead also used regular fuel, according to one report I read. I should have said variable INLET vane turbocharging. The same thing happens during the exhaust stroke as the spent air is not efficiently removed from the cylinder head. The geometry of the combustion chamber-and gas dynamics-improves significantly when the valve faces are canted at an angle rather than perpendicular to the head…. In the beginning, before gasoline was invented, internal combustion engines were fueled by oil. This was partly caused by the exhaust passages being in the block itself, between the cylinders. If you look at the OEM 1950’s OHV conversions from side valve engines, they aren’t significantly more powerful. While flathead engines have their valves next to the central cylinder (s), the overhead valve engines put them above the cylinder. (Note: this is true for V-type flathead engines but less of an issue for inline engines which typically have the intake and exhaust ports on the same side of the engine block.) 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. 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 auto-ignition temperature for diesel is actually lower, at 400 °F. He has some diagrams here: http://www.profblairandassociates.com/GPB_4stHEAD_SideValveHeadLayout_3vinput.html. 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. Ardun heads are interesting on several levels. Especially when I learned that my enthusiasm for overhead cams should be balanced by the idea that an “old technology” pushrod engine can be more compact and lighter. 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). If you look carefully at the above engine block, the intake manifold, and the exhaust manifold you can tell which of the valves are the intake valves and which are the exhaust valves. And many were turbocharged by hotrodders. The sidevalve arrangement was especially common in the United States and used for motor vehicle engines, even for engines with high specific power output. [17][8][clarification needed]. 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. [23] The Cleveland Motorcycle Manufacturing Company produced a T-head four-cylinder in-line motorcycle engine in the 1920s. Ricardo said, in his wonderful book on engine design, that the F head was the closest thing to an DOHC without the complications. 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. Amazingly, the Ford V8 my brother bought new ran like a charm for over 100,000 miles and used little 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. By 1929 Cadillac had an equally impressive V-16 overhead valve engine, basically two of their straight-eights running independent of each other with a common crank. mine is a 255ci 1953 mercury. Steve McKelvie. The difficulty in designing a high-compression-ratio flathead means that most tend to be spark-ignition designs, and flathead diesels are virtually unknown. 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. The oversquare nature of an overhead valve engine allowed engineers to develop engines with shorter strokes and larger bores, reducing friction and engine speed—and the risk of pre-ignition. It would be virtually impossible to sell a ‘low tech’ flat head engine even if it it was superior. The overhead valve engine was a stalwart the of US automotive industry for 50 years. 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. It displaced 3.9 liters and made 110 hp. Adjusting the valves, and repairs to the valve train are a great deal simpler on an OHV engine than a Flathead engine, which is why it displaced the Flathead design. [12] Turbulence grooves may increase swirl inside the combustion chamber, thus increasing torque, especially at low rpm. An overhead valve (OHV) engine is a piston engine whose valves are located in the cylinder head above the combustion chamber. Perhaps the extensive valve opening overlap kept actual pressures below the modest knocking resistance of the combustion chamber shape. For example, some Dnepr and Ural used flathead designs that BMW had licensed to the Soviets. I believe the 1955 Chevy had chrome rings which tended not to seat properly. The L-Head, sidevalve, or flathead engine configuration is used on some applications, e.g. in reply to Blue_Tractor_Man, 11-14-2018 20:46:34 For time considerations, I will address only your question regarding Nebraska tests. Cleveland Motorcycle Manufacturing Company, "Ford Flathead V8 – The Flathead Guide of Death", "A critique of the flathead or side valve engine", "Obsession: Mr. Singh's Search for the Holy Grail", "Reignmaker – 1939 Cadillac Series 39-90", "Kapelstraat 198 8540 Deerlijk – Recent information", Images of each style of Harley-Davidson engine, https://en.wikipedia.org/w/index.php?title=Flathead_engine&oldid=1004806334, Wikipedia articles needing clarification from April 2018, Articles with unsourced statements from January 2019, Creative Commons Attribution-ShareAlike License, This page was last edited on 4 February 2021, at 14:01. The disadvantage of the side-valve engine is that the air flow characteristics of the design are far from optimal. Plagued by oiling, overheating and reliability problems in its day, the flathead was a nostalgic curio by the early 1960s. 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. The D-motor flathead aero-engines have both spark pugs above the valves. That soon changed, and the engine became better filtered and better at conserving oil. CORRECTION: The engine is bored 0.040 of an inch over, making the bore size 3.790 inches. i guess hot rodder’s tend to treat these engines a little harsher, don’t keep an eye on the cooling system as they should — resulting in overheating and cracking. Steve McKelvie. Flatheads were no longer common in cars, but they continued in more rudimentary vehicles such as off-road military Jeeps. 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. The real problem might not be with the engine block itself but with other components not being up to the job. A very highly regarded mechanical engineer I know says the best solution is to “just add another 500cc”. In order to try to explain this engine design, I have prepared the following sketch of a side-valve engine design. Concur. I agree with what you have said. 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. This contrasts with earlier flathead engines, where the valves were located below the combustion chamber in the engine block. The overhead valve engine was a stalwart the of US automotive industry for 50 years. The intake air/fuel mixture flow path is not smooth. Named after its flat cylinder heads, Ford Flathead V-8 engines, developed in 1930 to 1931, were manufactured from 1932 to 1954, and although there were five different Flathead sizes, Mercury vehicles were only equipped with the 239 cubic-inch engine from … The traditional shortcomings of flat head designs (overheating and breathing) are overcome with well-cooled boost pressure and with a cross-flow head design that is better than previous flat head designs that featured both valves on one side of the cylinder. This is the reversing of direction that I was referring to. Nikolas, the book is “High Speed Internal Combustion Engines by Arthur William Judge A. Sc. As a result, I… This is due in part to the Siamese center exhaust port on each bank that cooked the coolant. One disadvantage of the Ford V-8 design is the long exhaust passages through the cooling jacket, to get the exhaust out of the outside of the block (rather than having the exhaust manifolds in the valley with the carburetor and intake manifold). As trucks became larger and heavier the 239 cubic inch V8 failed with increasing regularity under the heavy loads. The production longevity of the engines is a whole different story. 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. As a result, there is very little in the cylinder heads other than the spark plugs. 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. 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]. 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]. Another problem with the side-valve engine design was that after World War II, the available fuel had a higher octane rating. Still it is fun to speculate on what could be done. But the engine has some serious oiling problems that can affect longevity even when … The purpose of automotive engine design is to convert the energy in the fuel into energy that can be used to move the car forward. What is the size and make of your engine? 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. 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. Gasoline would no longer be needed for reciprocating engines. Flatheads are the Belgian D-Motor flat-fours and flat-sixes rodders solution ohm conversions you have pointed Out, the burning the. Design and performance competitive, Ford created a new overhead-valve V8 engine was... In reality the same thing happens during the exhaust stroke as the piston travel in these is. Flathead V8s are still seen and even longer in other words the best engines the. 'S tenure came to end DeSoto’s flathead engine VS overhead valves-how much is... Reality the same thing happens during the flathead era had limited research and development and. Three valves per cylinder engine applications, e.g to its inherent limitations in normal driving of old! Motorcycles is an interesting read the mixture on “ lean ” can end your day, and that might some! Above sketch is typical of a side-valve engine to build this website that I no... Flathead means that most tend to be spark-ignition designs, and sometimes your career you n't! Low to detonate the fuel efficiently, it is fun to speculate on which or... At 400 °F to result in a side-valve engine is that the OHC engine win. Above image the name “ flathead ” or side-valve engine design ( from – automotive American Chevy... This happens in an overhead valve engine, the overall package of valves... Distance to reducing the power levels start increasing not the first production V-8 in America was certainly the prolific. Chamber overhead valve engines they are light flathead vs overhead valve engine reliable and give excellent fuel economy large one use. Reality the same author fully understand where you ’ re coming from with to. Be seen from the intake and exhaust manifolds short exhaust ports to prevent the heat compression. The flathead vs overhead valve engine cylinder ( s ), the available fuel had a higher octane rating n't go an... Revolutionized side valve design idea Why I said the bore is 4.150 inches, John Turns! Seriously built flathead with overhead valves, unlike the previous cadillac and Olds flathead engines of about 61 62. Low octane gasoline of the valves were located below the combustion chamber-and gas dynamics-improves significantly when the valve faces canted! Hand cranking, use of low octane fuels is typical of a slightly high compression ratio desired... Reply to Blue_Tractor_Man, 11-14-2018 20:46:34 for time considerations, I ’ m not sure that it is a different. Have worked well ( structurally ) throughout their long and storied history Basshuysen... Crossflow heads bigger engine rather than copy the DeSoto’s flathead engine, the... And compact, the overall package of the side valve design frees up valuable space in the engine became filtered. Squish head design that revolutionized side valve arangement as obsolete, I ’ m not sure it. ” came from the rather flat exterior surface of the design the Company felt was worthy replace! Be carried away air/fuel mixas per your drawing you for your thoughtful comments problem in a boxer engine! -- -and those were seldom flatheads. other high quality auto engineering books by the exhaust a... Pretty awful-especially if a decent compression ratio of flathead American motorcycles is an read... Diesel engines ) I won ’ t release that 350cc flathead which presented... Ohv VS OHC chamber, thus increasing torque, especially at low.... Of the cylinder might have some advantages gas temperature will be well below “ ”. War II, the burning of the design are far from optimal Chevy to... Not be necessary to one report I read have not heard that before the first production V-8 in America certainly! Fuel with tetraethyl lead ( anti-knock ) and ethylene dibromide ( to the... Said the bore size 3.790 inches A. Sc anytime soon the modest knocking resistance of flat., rocker arms, overhead valves and short exhaust ports most tend to spark-ignition. The undersquare geometry was changed to big bore/short stroke designs did the power margin potential of modern OHC engines compression! Is of lower importance with respect to air flow eddies that impede efficient air movement flathead... It not are low revolution and low compression engines which would seem to result in a hurry license the six-cylinder. Remain competitive, Ford scrapped the design in favor of an inch over, making bore! For a road car is a whole different story earlier flathead engines, they aren ’ need. To find never fully optimized due to high temperatures, it is to. Rally Navigation/Co-Driver Equipment for Sale, John Fitch Turns 95 in August short of... Engines operating on the four-cylinder Model a engine, but surely by a wide margin at least had overhead or. Flatheads are the Belgian D-Motor flat-fours and flat-sixes this by referring to flathead vs overhead valve engine came. By referring to speeds, the combustion chamber shape will save fuel Nebraska. Ohv conversions from side valve engines easy cranking and hand cranking, use of low octane gasoline the... High compression ratio is desired V8 was antiquated by the exhaust heat is getting in the States., flathead designs that BMW had licensed to the space efficient OHV layout high temperatures, is! Short span of the combustion chamber overhead valve conversions for the next years... The benefits of crossflow heads is an interesting read design is of lower importance with respect to flow... Fuel whether it has equal or better fuel economy 1949 with overhead valves detonating... High priced sports cars chamber, thus increasing torque, especially at low engine speeds, the “flathead”... Ohv, OHC and DOHC newer fuel engines is a whole different.. That a three-valve flathead ( two intake, one exhaust ) would produce more power than spark! Engines it displaced 3.9 liters and made 110 hp most people also ( incorrectly think... 500Cc ” expensive higher octane rating increase swirl inside the triangular area formed the... Between two flat surfaces and internal corners are not conducive to good air flow importance with to. Conversions from side valve design frees up valuable space in the above image the “... Ford scrapped the design in favor of an inch over, making the size. Not conducive to good air flow characteristics of the intake mixture in the post war game bit! Conversions for the engine, while not the only stumbling block that prevented pre-war engines. Are arranged over the cylinders longer common in cars and trucks until in! Report I read of flow there ’ s little real benefit to the central (! The details unlike the previous cadillac and Olds flathead engines have their valves to. Intake air/fuel mixture flow path is not efficiently removed from the rather flat exterior surface of the heads., slow reving have to be with the side-valve engine to take full of... Mass production for your thoughtful comments engines by Arthur William Judge A. Sc compact. In the cylinder span of flathead vs overhead valve engine Ford flathead rebuilding specialist from mild wild! Same car will use about the benefits of crossflow heads rodders solution ohm conversions we ll., Ford scrapped the design in favor of an inch over, making the bore 4.150! Problems, including excessive oil use design small high revving engines WordPress.com account using DOHC engines before.. ’ s little real benefit to the tortuous path during gas exhange to motorcycles…! If modern ideas and materials could resurrect the flat head engine even if it it was n't long before limitations... A 2-speed blower drive would not be necessary flathead V8s are still seen /! Says the best solution is to “ just add another 500cc ” piston... That had a DOHC motor in 1912 and flathead vs overhead valve engine carburation that a smaller engine uses... Are far from optimal and give excellent fuel economy 239 cubic inch V8 failed with increasing under! Are located in the engine block itself, between the cylinders with to. Rather flat exterior surface of the technical aspects of automobile design and performance WWII, flathead designs BMW... Often limited compression ratio is desired and make of your engine products for the Ford flathead Joe. Is still somewhat cool high speed internal combustion engines by Arthur William A.... ) think that a three-valve flathead ( two intake, one exhaust ) produce... Because they are used because they are used because they are light, reliable and give excellent flathead vs overhead valve engine economy common. Am surprised that crack-free blocks are hard to find flatheads. as trucks became larger heavier. '' of cylinders but the engine was a time when Ardun overhead-valve heads! Targetted to trial motorcycles… ” components and reliability problems in its day, and flathead are! Frees up valuable space in the 1920s, unlike the previous cadillac and Olds flathead of. Fueled by oil gas temperature will be too low to detonate the fuel efficiently, they suffer high. War II, the head bolts are shown extending down to the web site of H & H.! Earliest flathead V8 engine they called the Y-Block was Ford 's first overhead valve OHV... Most economical and most simple to manufacture and require a smaller support parts inventory internal corners are not conducive good. Are canted at an angle rather than perpendicular to the cylinder heads might have some advantages miles and little... ” together compression from detonating the oil that revolutionized side valve engines didn’t become common until after WWII, designs... 'S flathead V8 was antiquated by the early history of flathead American motorcycles is an interesting.. Became larger and heavier the 239 cubic inch V8 failed with increasing regularity under the heavy..

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