Triumph 6 cylinder engine '67 through '76

[Andrew Mace]

Even more interesting was that quite literally at the other end of the building, Rover had the aluminum block v8, and would not share. Therby killing any chance the stag might have had.

Really? The story as I heard it was that Triumph wanted to go their own way on the Stag engine. Good engine actually, just underdeveloped at time of release and needed more attention than owners were willing to give....

By the time Rover had scored the V-8 from GM, British Leyland was already one big (un)happy family. I don't think there was any question of sharing or not sharing <span style="font-style: italic">per se</span> with various marques within BLMC; after all, Morgan used the engine in their +8 almost as soon as it appeared in the Rover! If anything, it might have been more a case of a: lingering stubbornness, and b: possibly a lack of manufacturing capacity, as well as the fact that Triumph had already developed the slant-four and, with it, their own V-8.

As I recall, it took an outsider making MGB V-8 conversions to finally shame MG/BLMC into doing it themselves!

 

[TR3driver]

Also, there was supposedly a report from the Triumph engineers that the so-called Rover V8 (actually a General Motors design sold to Rover after GM had too many problems with it) would not fit into the Stag. From what I have heard, that may have had some truth to it, as Rover had not yet developed the modified components that would allow it to fit in the Stag's rather cramped engine compartment. ("reverse" Oil pan and shortened water pump IIRC)

Also, it's my understanding that the original plan was for a "modular" V8 that could also be manufactured as a 4-cylinder. Not quite the same thing as "welding two 4-cylinders together". The original development was actually a joint venture with SAAB. (SAAB paid for much of the development, in return for training and rights to use the resulting design in their own cars.) The TR7 motor was actually a further development of the 4 pot version, and of course SAAB continued using the design for many years, making their own changes until it was quite successful for them.

The marketing folk may have had some input as well. Back then, a SOHC V8 was much sexier than a pushrod motor.

 

[jsfbond]

A freind of mine installed that same Buick (215)V8 into a 1960 MG Midget. What was commonly refered to as a Chinese car after completion.

 

[martx-5]

... The TR7 motor was actually a further development of the 4 pot version, and of course SAAB continued using the design for many years, making their own changes until it was quite successful for them.

I was working as a mechanic at a Saab dealer shortly after the first 99's started appearing with the Triumph engine. Huge number of warranty problems with it, mostly with the head. Actually, Saab didn't use it very long, by 1972, after four years, they <span style="font-weight: bold">substantially</span> redesigned the engine and began producing it themselves. It was know as the Saab B engine. We just called it the King Kong. It was pretty much bullet proof after the changes.

 

[swift6]

I was under the impression that the GT6 engine was a de-stroked version of the 2.5 block, resulting in the 2.0 for higher revs. designed for more bullit proof racing.

The 2.0 is essenntially a de-stroked version of the the 2.5 but the 2.0 came before the the 2.5, it wasn't developed from it. So in historical terms, the 2.5 litre version is a stroked version of the 2.0 litre. As Andy pointed out, the vitesse series started as an 803cc(?) 4 cylinder and kept getting bigger. The first 6 cylinder vitesse engine being 1.6 litre, bore size was increased to get to 2.0 litre and then stroked to get to 2.5 litre. The 2.5 litre was also the basis for the DOHC 2.3 litre and 2.6 litre I-6 used in the Rover SD1's. By the time that DOHC engine had finished development so many changes had been made that it had lost any real sense of lineage back to the vitesse series engines.

 

[Andrew Mace]

Right again, Shawn. Actually, I'm pretty sure the first six was a 2.0, as used in the Standard Vanguard Six models, circa 1960-61. It was then "sleeved down" to 1.6L for the Vitesse 6, and I vaguely recall that a 1.5L version was considered for some applications but never put into production. Similarly, there had been some plans to use (I think) the 1.6L version as a "base" engine in the big Triumph saloon introduced in 1963; we know that car as the 2000 and later the 2500 and 2.5, but that "base" model never came to be.

 

[jsfbond]

So being a carpenter type, I ask the question "If the short stroke of the race born design is great for higher revs, then why go to a longer stroked engine? Is displacement a just trade off for throwing more mass? Is the TR6 engine really that more powerfull?

 

[Andrew Mace]

Keep in mind that none of these engines was designed for racing! The wet-liner four was developed to give reasonably good power and long service and also to be easily "field-serviced" around the world, first in the Standard Vanguard and soon after in the Ferguson tractor. It was only after much "redevelopment" that the engine also became a decent powerplant for sporting cars. Similarly, the "SC" 803cc four-cylinder was also developed for a basic, economical car, and it was only much development and redesign that it became bigger, more powerful, etc., etc. Both engines dated from a time when long(ish)-stroke engines were still favored, in some part for tax reasons but also for basic power at lower revs! Thinking of any of these engines as short-stroke is really not accurate. Some came closer to being "square" but that was about it. The original 803cc four had (as previously noted) a 76mm stroke and a cylinder bore of only 58mm, only a bit larger in diameter than your typical Smiths/Jaeger fuel or temp. gauge!

 

[swift6]

Andy alluded to it in his above post, when he metioned the tax implications. The tax on the vehicle used to be based on the bore displacement. So the easy way to increase power without increasing the tax was to increase the stroke of the engine. If you look through the design of many British engines there is a historical trend of long stroke low revving engines. Even after the basis for taxation changed, the trend continued.

Toque was the key to power over horsepower with stroking the engines.

 

[ABCD]

The latest GT6 engine with recessed block and thick fire rings on the gasket used the thick head and domed pistons to get the higher compression ratio.