The Engine & Ancillaries

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1. THE ENGINE

The Standard-Triumph 6 cylinder engine was originally developed for the Standard Vanguard Luxury Six, which came out in 1960, see advert below:

  

The engine was an overhead valve design with  a cast-iron block and cylinder head, and a pressed-steel sump.The camshaft, which drove the distributor and oil pump through a spur gear, was itself chain-driven off the nose of the crankshaft, with the drive covered by a pressed-steel cover.

Beginnings: The SC four


The story of this engine starts with the Standard Eight of 1953 for which an entirely new 4-cylinder engine, known as the SC (small car) was designed by David Eley. Although new, the engine block had to be machined with tooling purchased for the Triumph Mayflower engine so the cylinder centre dimensions of the new 803cc engine were shared with the Mayflower's side valve 1247cc unit. This new in-line engine had overhead valves operated by push rods with the camshaft in the block, with both the cylinder block and head made of cast iron. It is notable for having both manifolds (exhaust and inlet) on the right hand side, and the distributor, camshaft, spark plugs and oil filter on the left-hand side, differentiating it from the similar capacity "A" series engine with which it is sometimes compared; they share the same bore and stroke (58 x 76mm) giving 803cc. The water pump is a separate casting mounted on the front of the cylinder head, indicating that the original 4 cylinder block may have been based on an earlier sidevalve engine with thermo-syphon cooling! The SC engine can be seen below:

Standard 8 Engine

The Six or 20S


Although the 6 cylinder engine was based on the 4 cylinder, David Eley, who was responsible for both, says that it "wasn't just a six-cylinder version of the SC" and talk of finding the seam where the additional 2 cylinders were added is wrong! It was not even manufactured in the same factory, being cast at Bean Industries (pictured below) which Standard-Triumph had just acquired (it's history goes back to the 'Bean' motor-car, click here to find out more). However it did share the location of the ports, distributor and camshaft, and had similar front and rear block faces. Below is a cut-away of the 2 litre engine, showing the position of the main components. Also the cylinders were siamesed i.e. cast with no water jacket between them, this was done so the engine would be short enough to fit into the Standard Vanguard 6. This also later helped when fitting the unit to small cars like the GT6 and Vitesse. However this also meant that there wasn't room to increase the capacity by enlarging the bores, the only way to do this was by increasing the stroke (see table below).

Although the cylinder head of the original 20S engine had individual inlet and exhaust ports from the start (unlike the SC engine), the breathing was not as efficient as it could be, this came with the inproved head design which came out in the mid to late 1960s as fitted to the GT6 Mk2 and TR5.

The original carburettors fitted were a Solex, which were not entirely successful (cold starting problems). Although SU carburettors were better, as they were made by competitor BMC, they couldn't be used. A similar variable choke carburettor had to be developed, and this was successfully done by Dennis Barbet of Alford & Alder (a wholly owned subsidiary of S-T). This new carburettor, which had rubber diaphragms, eventually became the Zenith Stromberg CD which was fitted to all the subsequent versions of the six-cylinder engine (until BMC became part of British Leyland, owners of Triumph). Strombergs can be seen in the picture below of the RHS of the engine. Another picture below shows the LHS of the engine showing from left to right the alternator, coil, distributor, mechanical petrol pump and below that the oil filter.

engine      engine LHS      engine RHS

Beans below, where the 20S engine and cylinder head were cast:

Beans Foundry


Engine 'Autopsy'

To see this at full size click on the picture below:


Various incarnations of the Standard-Triumph 6 cylinder engine
Year Bore & Stroke Capacity Power Car model
1962 66.8 x 76mm 1596cc 70bhp Triumph Vitesse 6
1960 74.7 x 76mm 1998cc 80bhp Standard Vanguard 6
1966 74.7 x 76mm 1998cc 95bhp Triumph Vitesse 2 Litre
1966 74.7 x 76mm 1998cc 95bhp Triumph GT6
1963 74.7 x 76mm 1998cc 90bhp Triumph 2000 Mk1
1969 74.7 x 76mm 1998cc - Triumph 2000 Mk2
1967 74.7 x 95mm 2498cc 150bhp Triumph TR5
1968 74.7 x 95mm 2498cc 80bhp Triumph TR6
1968 74.7 x 76mm 1998cc 105bhp Triumph GT6 Mk2
1968 74.7 x 95mm 2498cc 80bhp Triumph 2.5PI Mk1
1969 74.7 x 95mm 2498cc 80bhp Triumph 2.5PI Mk2
1970 74.7 x 76mm 1998cc 95bhp Triumph GT6 Mk3
1976 74.7 x 95mm 2498cc 80bhp Triumph 2500 Mk2

The Legacy - The new SD1 Six of 1977

When Triumph engineer Mike Loasby (who previously worked for Aston Martin) designed the successor to David Eley's Six (see below), elements of the original Triumph block were retained to allow continued use of existing casting and machining equipment, just as had previously been done with the original SC engine. Also cast by Bean Industries, the block was lengthened by 20mm, the bore and stroke dimensions of 81mm and 76mm/84mm were retained, and water passages were introduced between the cylinders. According to Robert Leitch on the AROnline website "Although it has received a bit rap in the trade thanks to its well-documented problems, the SD1 Six is a very capable engine. However, it could have been so much more had it been given the start it so richly deserved". Now somebody needs to build up a GT6 (Mk IV?) with this engine, which even in it's prototype stage could put out 150 bhp! To see the AROnline article click here.


See a Standard-Triumph - 6 cylinder Engine Animation by Williams Illustration

Animation

Click on the image above to see in youtube (the animation is fantastic!)



2. THE DISTRIBUTOR

Ignition on the GT6 is by a Delco-Remy D200 distributor (see below left), driven by a bevelled gear that meshes with a similar one on the camshaft (see below right). Delco stands for 'Dayton Engineering Laboratories Co.' and they were pioneers in battery ignition back in 1909. Remy was another American manufacturer of electrical equipment, both became a single division of GM in 1918 known as Delco-Remy. Triumph fitted Delco-Remy distributors to Spitfires and GT6s, probably with their predominant American market in mind. Other Triumphs were fitted with Lucas distributors, which, according to Martin Jay of Distributor Doctor are better quality.

      

Ignition is "timed" to occur just before the piston in cylinder 1 (nearest the front of the engine). According to Wikipedia "the need for advancing (or retarding) the timing of the spark is because fuel does not completely burn the instant the spark fires, the combustion gases  take a period of time to expand and the angular or rotational speed of the engine can lengthen or shorten the time frame in which the burning and expansion should occur. In a vast majority of cases, the angle will be described as a certain angle advanced before top dead center (BTDC)".  Static timing for the Triumph 6 cylinder engines should be 10 degs. BTDC. Dynamic timing (controlled by centrifugal weights within the distributor) should be as the table below (with the curve further below):

Ignition Distributor - Centrifugal Advance
(GT6 2 litre engine)
RPM Degrees Crankshaft (max)
500 0.0
900 3.8
1650 11.0
2400 12.8
3600 15.6
4800 18.6
5000 19.0


3. THE COIL

A coil, which acts as a step-up transformer,  provides the high voltage (around 40,000 volts) needed by the spark plugs to ignite the mixture in the engine. Coils have two 'windings' around a common core, the primary which is connected to a 12v supply (the battery) and the secondary which outputs the high voltage for the spark at the plugs.

The normal coil fitted to the GT6 is a Lucas HA12. HA refers to High Performance (Standard is LA, BA is an older coding for coils used with a ballast resistor & SA is Sports). The currently available equivalent is known as a DLB105 which has a primary resistance of 3 ohms to suit non ballast resisted ignition.

Ballast resisted ignition systems were developed (by Ford in around 1970) to overcome problems with poor cold starting. As the starter takes nearly all the current to turn over the cold engine, it starves the coil of the current needed to provide a nice spark. A ballast resisted coil will have fewer turns so will have a DC resistance of 1.5 ohms instead of the usual 3 ohms. It will give a good spark with only a 9 volts supply. The coil will need two wires or feeds connected to the +ve terminal, one from the ignition which goes through the ballast resistor to give a constant 9v when the engine is running, and one from the solenoid activated by the starter switch giving the full 12v which in a coil rated at 9v provides a 'supercharged' spark to the plugs during starting. The Lucas ballast resistor fitted to the GT6 Mk3 is shown below:

 It is critical, therefore, that a 1.5 ohm coil is fitted with a ballast resisted ignition and a 3 ohm coil to a non ballast resisted ignition! Generally the various GT6 models were as the table below (as per the official workshop manual):

Model Coil Manufacturer Type Primary Winding Resistance Ballast Resistor Type
GT6 Mk1 Lucas HA12 3.0 to 3.5  Ω Not fitted
GT6 Mk2 Lucas HA12 3.0 to 3.5  Ω Not fitted
GT6 Plus Lucas HA12 3.0 to 3.5  Ω Not fitted
GT6 Mk3 (early) Lucas 16C6 1.43 to 1.58 Ω Lucas 3BR
GT6 Mk3 (late) Lucas 2400 1.3 to 1.5  Ω Wire

As can be seen above, the ballast resistor was introduced in the October 1970 GT6 Mk3. Later GT6s had a resisted wire instead. A section of the GT6 Mk3 Wiring Diagram can be seen below:

The wire from the ballast resistor to the Solenoid is WY (White/Yellow).


A table showing the values for non-ballast resisted and ballast resisted ignitions is shown below. The nominal voltage given by a 12v battery is 12.6v which gives 52.9 watts power to the ignition with non-ballast resisted ignition (1st row). When ballast resisted ignition is in starting mode (i.e. the ballast resistor is bypassed, 2nd row) a power of 48.2 watts to the ignition is given, even when the voltage drops to 8.5v as can happen when a large proportion of current goes to the starter motor, as when the engine is cold. After the car has started (3rd row) the ballast resistor kicks in to increase the total resistance to 3 ohms, which gives 52.9 watts power to the ignition. With a 1.5 ohm coil but without the ballast resistor (4th row), the power would be double, around 105 watts, which would burn out the ignition, hence the need for a 1.5 ohm ballast resistor with a 1.5 ohm coil! Incidentally later cars didn't have the ballast resistor as shown above, instead they had a 1.5 ohm wire which had the same effect.

Coil Coil Resistance Ballast Resistor Total Resistance Amperage Volts Power (watts)
For non-ballasted ignition 3.0 ohms Not fitted 3.0 ohms 4.2 12.6 52.9
For ballasted ignition (starting mode) 1.5 ohms Not fitted 1.5 ohms 5.7 8.5 48.2
For ballasted ignition (running mode) 1.5 ohms 1.5 ohms 3.0 ohms 4.2 12.6 52.9
Car running with 1.5 ohm coil, but no ballast resistor 1.5 ohms Not fitted 1.5 ohms 8.4 12.6 105.8

To watch a very clear explanation of ballast resistors on YouTube, courtesy of  Moss Motoring, click here.


4. THE SPARK PLUGS

The spark plugs normally fitted are the trusty Champion N9Ys.  Albert Champion was a Frenchman who immigrated to the United States in 1889 to race bicycles and motorcycles. He also set up a side business, manufacturing and selling spark plugs in Boston, Massachusetts, as a means of income. William Durant, the founder of General Motors in the USA, spotted Champion’s potential and moved him and his operation to Flint, Michigan, in 1904. The Champion Ignition Company was formed. Over the next few years, Champion lost control of the company, he left and subsequently setup the AC spark plug company in 1908. GM’s production of motor vehicles grew significantly and GM Corp purchased the AC spark plug company in 1909 to service their ever increasing needs. Champion spark plugs used to be made in Upton in the Wirral until the factory closed in 2006. They are now made in Italy.

The N9Y has a 19mm reach, a M4 thread and is 14mm in diameter. The single electrode is made from standand nickel.


5. THE FUEL PUMP

One of the most common type of fuel pumps used in automobiles was the single action, diaphragm-type mechanical pump (before the advent of modern electronic fuel injection). A diaphragm type fuel pump is usually mounted on the engine and is operated by an eccentric lobe on the camshaft. The GT6 is fitted with 2 different types of fuel pump, originally made by AC, the division of General Motors originally founded by Albert Champion of spark plug fame (see above). The GT6 Mk1 was fitted with the version with a glass sediment bowl, as were many Fords of the 50s and 60s, as per the first picture below. This didn't contain a filter (fitting a separate filter is recommended) but at least one could see if there was any sediment!  Later models of GT6 were fitted with the brass top version, as per the second picture below.

      

The AC fuel pump is shown in more detail below:

I don't think the current replacement pumps are any longer made by AC, but probably by a manufacturer in the Far East. Repair kits for the originals are available. The one below is sold by ANG but others are, of course, widely available. I have no personal experience of these, but a 'new' pump I obtained from James Paddock did leak when the car was on a slope, but this was cured by fitting the fibre washer they subsequently sent me, under the top locating screw.