IOE engine
Encyclopedia
The intake/inlet over exhaust (IOE) engine, also known as F-head and pocket valve
, is a valvetrain
configuration used in early four-stroke
internal combustion engine
s. The configuration consists of intake valves located in the cylinder head
and exhaust valves located in the cylinder or engine block
.
used a more advanced form of IOE engine. It was designed by Jack Swaine in the mid-late 1940s and was in production from 1948 to the early 1980s. Unlike the F-head, this had an efficient combustion chamber designed for good combustion, rather than simple manufacture. The top surface of the block was machined at an angle, with the piston crowns angled in a "pitched roof" to match. At TDC, the piston almost touched the angled inlet valve and provided good 'squish' to the combustion chamber itself, offset to the side by half a cylinder diameter. The resultant combustion chamber shape was a near-ideal hemisphere, although inverted and tilted from the usual "hemi-head" design. The spark plug was centrally mounted and this, together with the turbulence generated by the squish, provided a short flame path. The thinness of the gas layer between piston and inlet valve was so confined as to reduce the risk of detonation on poor fuel, one factor that kept it in service with Land Rover for so long. During the late 1940s and early 1950s when the only petrol available was low octane
'pool' petrol it also allowed Rover to run higher compression ratios than many competitors with the more usual side valve (flat head) or overhead valve
designs.
The unusual combustion chamber arrangement with its angled valves also lead to an unusual valve train. The block-mounted camshaft operates small wedge shaped rockers, one for each valve. In early models the camshaft acts on a simple pad on the rocker, but for later models this pad was replaced by a roller follower. The exhaust rockers act directly on the valves, whilst the inlet rockers act on pushrods running up to a second set of longer flat rockers operating the inlet valves. The Rover engine, like many 1940s designs, was a small bore, long stroke engine to keep the RAC HP rating as low as possible, thus keeping the road tax as low as possible. The IOE layout enabled Rover to use much larger valves than would normally be possible in a small bore engine, allowing much better breathing and better performance.
The shape of the combustion chamber as an "inverted hemi-head", along with the angled cylinder head joint and pitched-roof piston crowns, had earlier been used in the 1930 Van Ranst
-designed Packard
V12 engine, although in this case the valves were both in the block as side valves and the spark plug
was poorly placed at the extremity of the combustion chamber.
The Rover IOE engine family encompassed straight-4 (1.6- and 2.0-litres) and straight-6 (2.1-, 2.2-, 2.3-, 2.4-, 2.6- and 3.0-litres) engines and powered much of the company's post-war range in the form of the P3
, P4
and P5
models. Adapted versions of the 1.6 and 2.0 IOE engines were used in early version of the Land Rover
as well. Power outputs ranged from 50bhp (Land Rover 1.6) to 134bhp (P5
3 litre MkII & III). The 2.6 6-cylinder IOE engine had a particularly long career. After being used in Rover P4
saloon cars it was added to long-wheelbase Land Rover models from 1963 in the 2A Forward Control models, then in 1967 in the bonneted 109", and remained an optional fitment until 1980 when it was replaced by the Rover V8.
used IOE engines with atmospheric inlet valves until 1912, and with mechanically driven inlet valves from 1911 to the late 1920s. Indian
used IOE valvetrains on all of their four cylinder bikes except those built in 1936 and 1937. Other American motorcycle manufacturers that use IOE engines include Excelsior
, Henderson
, and Ace
.
Hudson
used an IOE straight-six engine from 1927 to 1929. Willys
, and its successor Kaiser-Jeep, used variants of the Willys Hurricane engine
from 1950 to 1971. Rolls-Royce
used variants of their B60 IOE straight-six engine in their Wraith
and Silver Wraith
cars. A short-stroke oversquare version of the B60 engine was also used in the Princess 4-litre-R saloon car, displacing 3909cc and producing around 175 hp (manufacturers figures). This was known as the FB60 and was substantially upgraded from the common-or-garden B60 - it had hydraulic lifters, different carburation, hotter cam and other improvements. These changes liberated a 55 hp increase from the B60 engines' 120 hp output. Over 6000 of these cars were made.
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...
, is a valvetrain
Valvetrain
Valvetrain is an all-encompassing term used to describe the mechanisms and parts which control the operation of the valves. A traditional reciprocating internal combustion engine uses valves to control air and fuel flow into and out of the cylinders, facilitating combustion.-Layout:Valvetrain: The...
configuration used in early four-stroke
Four-stroke cycle
A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.There are two...
internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s. The configuration consists of intake valves located in the cylinder head
Overhead valve
An overhead valve engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block , and uses pushrods or rods to actuate rocker arms above the cylinder...
and exhaust valves located in the cylinder or engine block
Flathead engine
A flathead engine 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...
.
Description
In a F-head engine, the intake manifold and its valves are located atop the cylinders, in the cylinder head, and are operated by rocker arms which reverse the motion of the pushrods so that the intake valves open downward into the combustion chamber. The exhaust manifold and its valves are located beside or as part of the cylinders, in the block. The exhaust valves are either roughly or exactly parallel with the pistons; their faces point upwards and they are not operated by pushrods, but by contact with a camshaft through the tappet or valve lifter.Origin
The earliest IOE layouts used atmospheric inlet valves which were held closed with a weak spring and were opened by the suction created when the piston went down on the inlet stroke. When the limits of this system were reached, the design was improved without substantial changes to the head casting by adding a mechanical system to open the inlet valves and stronger springs to close them. In both cases, the exhaust valves were in the block and were opened by contact with a camshaft through a tappet or valve lifter and closed by springs.Advantages
The IOE design allowed the use of much larger valves than a side valve or overhead valve engine. Its advantages over the flathead also included better intake mixture flow and greater reliability from its cooling of the exhaust valve and its spring.Rover IOE engines
RoverRover P3
The Rover P3 car produced by the Rover company in 1948 and 1949 was very much an interim model.For the post-war market Rover had a new engine that had been in preparation since the late 1930s with overhead inlet and side exhaust valves. It was made in two version for the car, the "60" had a...
used a more advanced form of IOE engine. It was designed by Jack Swaine in the mid-late 1940s and was in production from 1948 to the early 1980s. Unlike the F-head, this had an efficient combustion chamber designed for good combustion, rather than simple manufacture. The top surface of the block was machined at an angle, with the piston crowns angled in a "pitched roof" to match. At TDC, the piston almost touched the angled inlet valve and provided good 'squish' to the combustion chamber itself, offset to the side by half a cylinder diameter. The resultant combustion chamber shape was a near-ideal hemisphere, although inverted and tilted from the usual "hemi-head" design. The spark plug was centrally mounted and this, together with the turbulence generated by the squish, provided a short flame path. The thinness of the gas layer between piston and inlet valve was so confined as to reduce the risk of detonation on poor fuel, one factor that kept it in service with Land Rover for so long. During the late 1940s and early 1950s when the only petrol available was low octane
Octane
Octane is a hydrocarbon and an alkane with the chemical formula C8H18, and the condensed structural formula CH36CH3. Octane has many structural isomers that differ by the amount and location of branching in the carbon chain...
'pool' petrol it also allowed Rover to run higher compression ratios than many competitors with the more usual side valve (flat head) or overhead valve
Overhead valve
An overhead valve engine, also informally called pushrod engine or I-head engine, is a type of piston engine that places the camshaft within the cylinder block , and uses pushrods or rods to actuate rocker arms above the cylinder...
designs.
The unusual combustion chamber arrangement with its angled valves also lead to an unusual valve train. The block-mounted camshaft operates small wedge shaped rockers, one for each valve. In early models the camshaft acts on a simple pad on the rocker, but for later models this pad was replaced by a roller follower. The exhaust rockers act directly on the valves, whilst the inlet rockers act on pushrods running up to a second set of longer flat rockers operating the inlet valves. The Rover engine, like many 1940s designs, was a small bore, long stroke engine to keep the RAC HP rating as low as possible, thus keeping the road tax as low as possible. The IOE layout enabled Rover to use much larger valves than would normally be possible in a small bore engine, allowing much better breathing and better performance.
The shape of the combustion chamber as an "inverted hemi-head", along with the angled cylinder head joint and pitched-roof piston crowns, had earlier been used in the 1930 Van Ranst
C. W. Van Ranst
Cornelius "C. W." Van Ranst was an American racecar driver who competed in the 1921 Indianapolis 500....
-designed Packard
Packard
Packard was an American luxury-type automobile marque built by the Packard Motor Car Company of Detroit, Michigan, and later by the Studebaker-Packard Corporation of South Bend, Indiana...
V12 engine, although in this case the valves were both in the block as side valves and the spark plug
Spark plug
A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...
was poorly placed at the extremity of the combustion chamber.
The Rover IOE engine family encompassed straight-4 (1.6- and 2.0-litres) and straight-6 (2.1-, 2.2-, 2.3-, 2.4-, 2.6- and 3.0-litres) engines and powered much of the company's post-war range in the form of the P3
Rover P3
The Rover P3 car produced by the Rover company in 1948 and 1949 was very much an interim model.For the post-war market Rover had a new engine that had been in preparation since the late 1930s with overhead inlet and side exhaust valves. It was made in two version for the car, the "60" had a...
, P4
Rover P4
The Rover P4 series was a group of saloon automobiles produced from 1949 through to 1964 designed by Gordon Bashford. The P4 designation is factory terminology for the group of cars and was not in day-to-day use by ordinary owners, who would have said simply that they had a "Rover 90" and so on.The...
and P5
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
models. Adapted versions of the 1.6 and 2.0 IOE engines were used in early version of the Land Rover
Land Rover Series
The Land Rover Series I, II, and III are off-road vehicles produced by the British manufacturer Land Rover that were inspired by the US-built Willys Jeep...
as well. Power outputs ranged from 50bhp (Land Rover 1.6) to 134bhp (P5
Rover P5
The Mark II version of the P5 was introduced in 1962. It featured more power from the same 3.0 L engine and an improved suspension, while dropping the glass wind deflectors from the top of the window openings which also, on the front doors, now featured "quarterlight" windows .The most...
3 litre MkII & III). The 2.6 6-cylinder IOE engine had a particularly long career. After being used in Rover P4
Rover P4
The Rover P4 series was a group of saloon automobiles produced from 1949 through to 1964 designed by Gordon Bashford. The P4 designation is factory terminology for the group of cars and was not in day-to-day use by ordinary owners, who would have said simply that they had a "Rover 90" and so on.The...
saloon cars it was added to long-wheelbase Land Rover models from 1963 in the 2A Forward Control models, then in 1967 in the bonneted 109", and remained an optional fitment until 1980 when it was replaced by the Rover V8.
Other users
The IOE valvetrain layout was used extensively in American motorcycles. Harley-DavidsonHarley-Davidson
Harley-Davidson , often abbreviated H-D or Harley, is an American motorcycle manufacturer. Founded in Milwaukee, Wisconsin, during the first decade of the 20th century, it was one of two major American motorcycle manufacturers to survive the Great Depression...
used IOE engines with atmospheric inlet valves until 1912, and with mechanically driven inlet valves from 1911 to the late 1920s. Indian
Indian (motorcycle)
Indian is an American brand of motorcycles. Indian motorcycles were manufactured from 1901 to 1953 by a company in Springfield, Massachusetts, USA, initially known as the Hendee Manufacturing Company but which was renamed the Indian Manufacturing Company in 1928. The Indian factory team took the...
used IOE valvetrains on all of their four cylinder bikes except those built in 1936 and 1937. Other American motorcycle manufacturers that use IOE engines include Excelsior
Excelsior Motor Manufacturing & Supply Company
Excelsior Motor Manufacturing & Supply Company was a U.S. motorcycle manufacturer operating in Chicago from 1907 to 1931. It was purchased by Ignaz Schwinn, proprietor of bicycle manufacturer Arnold, Schwinn & Co. in 1912. The Henderson Motorcycle Company became a division of Excelsior when...
, Henderson
Henderson Motorcycle
Henderson produced 4-cylinder motorcycles from 1912 until 1931. They were the largest and fastest motorcycles of their time, and appealed to sport riders and police departments. Police favored them for traffic patrol because they were faster than anything on the roads...
, and Ace
Ace Motor Corporation
Ace Motor Corporation was a motorcycle manufacturer in operation continuously in Philadelphia, Pennsylvania between 1919 and 1924 and intermittently afterward until 1927...
.
Hudson
Hudson Motor Car Company
The Hudson Motor Car Company made Hudson and other brand automobiles in Detroit, Michigan, from 1909 to 1954. In 1954, Hudson merged with Nash-Kelvinator Corporation to form American Motors. The Hudson name was continued through the 1957 model year, after which it was dropped.- Company strategy...
used an IOE straight-six engine from 1927 to 1929. Willys
Willys
Willys was the brand name used by Willys-Overland Motors, an American automobile company best known for its design and production of military Jeeps and civilian versions during the 20th century.-Early History:In 1908, John Willys bought the Overland Automotive Division of Standard Wheel Company...
, and its successor Kaiser-Jeep, used variants of the Willys Hurricane engine
Willys Hurricane engine
The Willys F4-134 Hurricane was an inline-4 piston engine and powered the famous Jeep CJ in the CJ-3B, CJ-5, and CJ-6 models. It was also used in the Willys 473 and 475 pickups, wagons, and sedan deliveries...
from 1950 to 1971. Rolls-Royce
Rolls-Royce Limited
Rolls-Royce Limited was a renowned British car and, from 1914 on, aero-engine manufacturing company founded by Charles Stewart Rolls and Henry Royce on 15 March 1906 as the result of a partnership formed in 1904....
used variants of their B60 IOE straight-six engine in their Wraith
Rolls-Royce Wraith
The Rolls-Royce Wraith was built by Rolls-Royce at their Derby factory from 1938 to 1939 and supplied to independent coachbuilders as a running chassis....
and Silver Wraith
Rolls-Royce Silver Wraith
For information on the Silver Wraith II, see Rolls-Royce Silver Shadow.The Silver Wraith was the first post-war Rolls-Royce model and was made at the Crewe factory from 1946 to 1959....
cars. A short-stroke oversquare version of the B60 engine was also used in the Princess 4-litre-R saloon car, displacing 3909cc and producing around 175 hp (manufacturers figures). This was known as the FB60 and was substantially upgraded from the common-or-garden B60 - it had hydraulic lifters, different carburation, hotter cam and other improvements. These changes liberated a 55 hp increase from the B60 engines' 120 hp output. Over 6000 of these cars were made.