The Triumph Six Cylinder or Triumph I6 engine is a compact, reliable and in some configurations, relatively powerful straight-six engine using traditional cast iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 construction and a pushrod actuated 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...

 head, originally introduced by Standard Triumph in their Standard Vanguard

Standard Vanguard

The car used a conventional chassis on which was mounted the American inspired semi-streamlined four-door body, which resembles a Plymouth. Suspension was independent at the front with coil springs and a live axle and leaf springs at the rear. Front and rear anti-roll bars were fitted. The brakes...

. It has been used in a range of vehicles including some kit cars.

History

The engine began life as an 803 cc 4 cylinder unit used in the Standard Eight

Standard Eight

The Flying Eight was the smallest member of the Standard Flying family.Introduced in 1938 or 1939 , the Flying Eight featured, in its saloon form, the "streamlined" body of the little Standard Flying Nine which had appeared in 1937...

 in 1953, it was modified a number of times for use in the Triumph Herald

Triumph Herald

The Triumph Herald was a small two-door car introduced in 1959 by the Standard-Triumph Company of Coventry. Body design was by the Italian stylist Michelotti and the car was offered in saloon, convertible, coupé, van, and estate models....

, and Triumph Spitfire

Triumph Spitfire

The Triumph Spitfire is a small English two-seat sports car, introduced at the London Motor Show in 1962. The vehicle was based on a design produced for Standard-Triumph in 1957 by Italian designer Giovanni Michelotti...

.

First for the 948 cc Herald, then for the 1147 cc Herald 1200 the Cylinders were re-aligned to give better clearance for the head studs and allow the bore to be enlarged. The engine was further developed and bored from 69.3 mm (2.7 in) in the 1147 cc version to 73.7 mm (2.9 in) giving 1296 cc for the Herald 13/60, the stroke was also increased from 76 mm (3 in) to 86.5 mm (3.4 in) providing 1493 cc for the Spitfire 1500.

At the same time there was another project at Triumph to provide a more sporty version of the Herald, and it was decided to add two extra cylinders giving 1596 cc and the familiar 6 cylinder engine was born, a very small 6 cylinder engine and something which Mazda made a selling point in their designs years later.

The story continued much as before with ongoing increases in bore size and stroke, and soon another bore change up to 74.6 mm (2.9 in) gave a 2 litre version used in the Standard Vanguard

Standard Vanguard

The car used a conventional chassis on which was mounted the American inspired semi-streamlined four-door body, which resembles a Plymouth. Suspension was independent at the front with coil springs and a live axle and leaf springs at the rear. Front and rear anti-roll bars were fitted. The brakes...

 and Triumph 2000

Triumph 2000

The Triumph 2000 is a mid-sized, rear wheel drive automobile which was produced in Coventry by the Triumph Motor Company between 1963 and 1977. Larger-engined models, known as the Triumph 2.5 PI and Triumph 2500 were also produced.-Engine:...

 and proved to be a very smooth engine, not giving away any of its earlier origins.

When the range of TR sportscars needed a refresh, and the old 4 cylinder engine did not deliver the power required the stroke of the 6 cylinder engine was again increased to a huge 95 mm (3.7 in) giving 2498 cc. Quite amazing when you consider that the original version was only 803 cc.

This new 2.5 litre version gave a respectable 150 bhp in the TR5 when equipped with the Lucas mechanical fuel injection system, although the car was sold in the US with Stromberg carburettors to avoid the need for additional emissions control systems and unfortunately this reduced the power to 105 bhp.

Technical

A partial chart of triumph engine numbers is posted on the "Spitfire & GT6 magazine" site. However the capacity appears not to match the bore/stroke, or that published on other sites including the GT6 Ezine, hence the corrections in the tables below.

Engine Applications Chart

Engine No. Prefix	Capacity	Car
HB	1596 cc	Vitesse 6
HC	1998 cc	Vitesse 2 Litre
KC	1998 cc	GT6 Mk1/2
KD	1998 cc	GT6 Mk1/2 (Anti Smog) (US?)
KE	1998 cc	GT6 Mk3
KF	1998 cc	GT6 Mk3 (US)
KG	1998 cc	GT6 Mk3 (Sweden)
MB	1998 cc	2000 Mk1
MB	1998 cc	2000 Mk1
MG, MM, MN	2498 cc	2500
ME, ML	1998 cc	2000 Mk2
CC	2498 cc	TR250 & TR6
CF	2498 cc	TR6
CP, CR	2498 cc	TR6(injection) and TR5PI

Factory Quoted Power Chart

Model	Quoted power @rpm	Quoted torque @rpm	Capacity
TR5	150 bhp @5500	164 lbft @3500	2498 cc
TR250	104 bhp @4500	143 lbft @3000	2498 cc
TR6 (69-72)	150 bhp @5500	164 lbft @3500	2498 cc
TR6 (73...)	124 bhp @5000	143 lbft @3500	2498 cc
TR6 (USA)	104 bhp @4500	143 lbft @3000	2498 cc
2.5 PI Mk1 & Mk2	132 bhp @5500	153 lbft @2000	2498 cc
2500 Mk2	99 bhp @4700	133 lbft @3000	2498 cc
2500 TC	106 bhp @4700	139 lbft @3000	2498 cc
2000 Mk1	90 bhp @5000	117 lbft @2900	1998 cc
2000 Mk2	84 bhp @5000	100 lbft @2900	1998 cc
2000 TC	91 bhp @4750	110 lbft @3300	1998 cc
GT6 Mk1	95 bhp @5000	117 lbft @3000	1998 cc
GT6 Mk2	104 bhp @5300	117 lbft @3000	1998 cc
GT6+	95 bhp @4700	117 lbft @3400	1998 cc
Vitesse 6	70 bhp @5000	92 lbft @2800	1596 cc
Vitesse 2L	95 bhp @5000	117 lbft @3000	1998 cc
Vitesse Mk2	104 bhp @5300	117 lbft @3000	1998 cc

Racing

Triumph did start to race Spitfires, and some early GT6 prototypes at Le Mans, with some good success, and later at Sebring but due to rule changes and the takeover by Leyland, this was not continued.